diff --git a/fs/btrfs/Kconfig b/fs/btrfs/Kconfig
index d33f01c..5f583c8a 100644
--- a/fs/btrfs/Kconfig
+++ b/fs/btrfs/Kconfig
@@ -6,6 +6,9 @@
 	select ZLIB_DEFLATE
 	select LZO_COMPRESS
 	select LZO_DECOMPRESS
+	select RAID6_PQ
+	select XOR_BLOCKS
+
 	help
 	  Btrfs is a new filesystem with extents, writable snapshotting,
 	  support for multiple devices and many more features.
diff --git a/fs/btrfs/Makefile b/fs/btrfs/Makefile
index 7df3e0f..3932224 100644
--- a/fs/btrfs/Makefile
+++ b/fs/btrfs/Makefile
@@ -8,7 +8,7 @@
 	   extent_io.o volumes.o async-thread.o ioctl.o locking.o orphan.o \
 	   export.o tree-log.o free-space-cache.o zlib.o lzo.o \
 	   compression.o delayed-ref.o relocation.o delayed-inode.o scrub.o \
-	   reada.o backref.o ulist.o qgroup.o send.o dev-replace.o
+	   reada.o backref.o ulist.o qgroup.o send.o dev-replace.o raid56.o
 
 btrfs-$(CONFIG_BTRFS_FS_POSIX_ACL) += acl.o
 btrfs-$(CONFIG_BTRFS_FS_CHECK_INTEGRITY) += check-integrity.o
diff --git a/fs/btrfs/compression.c b/fs/btrfs/compression.c
index 94ab2f8..15b9408 100644
--- a/fs/btrfs/compression.c
+++ b/fs/btrfs/compression.c
@@ -372,7 +372,7 @@
 		page = compressed_pages[pg_index];
 		page->mapping = inode->i_mapping;
 		if (bio->bi_size)
-			ret = io_tree->ops->merge_bio_hook(page, 0,
+			ret = io_tree->ops->merge_bio_hook(WRITE, page, 0,
 							   PAGE_CACHE_SIZE,
 							   bio, 0);
 		else
@@ -655,7 +655,7 @@
 		page->index = em_start >> PAGE_CACHE_SHIFT;
 
 		if (comp_bio->bi_size)
-			ret = tree->ops->merge_bio_hook(page, 0,
+			ret = tree->ops->merge_bio_hook(READ, page, 0,
 							PAGE_CACHE_SIZE,
 							comp_bio, 0);
 		else
diff --git a/fs/btrfs/ctree.h b/fs/btrfs/ctree.h
index 1679051..3dcedfe 100644
--- a/fs/btrfs/ctree.h
+++ b/fs/btrfs/ctree.h
@@ -506,6 +506,7 @@
 #define BTRFS_FEATURE_INCOMPAT_BIG_METADATA	(1ULL << 5)
 
 #define BTRFS_FEATURE_INCOMPAT_EXTENDED_IREF	(1ULL << 6)
+#define BTRFS_FEATURE_INCOMPAT_RAID56		(1ULL << 7)
 
 #define BTRFS_FEATURE_COMPAT_SUPP		0ULL
 #define BTRFS_FEATURE_COMPAT_RO_SUPP		0ULL
@@ -515,6 +516,7 @@
 	 BTRFS_FEATURE_INCOMPAT_MIXED_GROUPS |		\
 	 BTRFS_FEATURE_INCOMPAT_BIG_METADATA |		\
 	 BTRFS_FEATURE_INCOMPAT_COMPRESS_LZO |		\
+	 BTRFS_FEATURE_INCOMPAT_RAID56 |		\
 	 BTRFS_FEATURE_INCOMPAT_EXTENDED_IREF)
 
 /*
@@ -956,6 +958,8 @@
 #define BTRFS_BLOCK_GROUP_RAID1		(1ULL << 4)
 #define BTRFS_BLOCK_GROUP_DUP		(1ULL << 5)
 #define BTRFS_BLOCK_GROUP_RAID10	(1ULL << 6)
+#define BTRFS_BLOCK_GROUP_RAID5    (1 << 7)
+#define BTRFS_BLOCK_GROUP_RAID6    (1 << 8)
 #define BTRFS_BLOCK_GROUP_RESERVED	BTRFS_AVAIL_ALLOC_BIT_SINGLE
 
 enum btrfs_raid_types {
@@ -964,6 +968,8 @@
 	BTRFS_RAID_DUP,
 	BTRFS_RAID_RAID0,
 	BTRFS_RAID_SINGLE,
+	BTRFS_RAID_RAID5,
+	BTRFS_RAID_RAID6,
 	BTRFS_NR_RAID_TYPES
 };
 
@@ -973,6 +979,8 @@
 
 #define BTRFS_BLOCK_GROUP_PROFILE_MASK	(BTRFS_BLOCK_GROUP_RAID0 |   \
 					 BTRFS_BLOCK_GROUP_RAID1 |   \
+					 BTRFS_BLOCK_GROUP_RAID5 |   \
+					 BTRFS_BLOCK_GROUP_RAID6 |   \
 					 BTRFS_BLOCK_GROUP_DUP |     \
 					 BTRFS_BLOCK_GROUP_RAID10)
 /*
@@ -1197,6 +1205,10 @@
 	u64 flags;
 	u64 sectorsize;
 	u64 cache_generation;
+
+	/* for raid56, this is a full stripe, without parity */
+	unsigned long full_stripe_len;
+
 	unsigned int ro:1;
 	unsigned int dirty:1;
 	unsigned int iref:1;
@@ -1242,6 +1254,23 @@
 	ORPHAN_CLEANUP_DONE	= 2,
 };
 
+/* used by the raid56 code to lock stripes for read/modify/write */
+struct btrfs_stripe_hash {
+	struct list_head hash_list;
+	wait_queue_head_t wait;
+	spinlock_t lock;
+};
+
+/* used by the raid56 code to lock stripes for read/modify/write */
+struct btrfs_stripe_hash_table {
+	struct list_head stripe_cache;
+	spinlock_t cache_lock;
+	int cache_size;
+	struct btrfs_stripe_hash table[];
+};
+
+#define BTRFS_STRIPE_HASH_TABLE_BITS 11
+
 /* fs_info */
 struct reloc_control;
 struct btrfs_device;
@@ -1341,6 +1370,13 @@
 	struct mutex cleaner_mutex;
 	struct mutex chunk_mutex;
 	struct mutex volume_mutex;
+
+	/* this is used during read/modify/write to make sure
+	 * no two ios are trying to mod the same stripe at the same
+	 * time
+	 */
+	struct btrfs_stripe_hash_table *stripe_hash_table;
+
 	/*
 	 * this protects the ordered operations list only while we are
 	 * processing all of the entries on it.  This way we make
@@ -1423,6 +1459,8 @@
 	struct btrfs_workers flush_workers;
 	struct btrfs_workers endio_workers;
 	struct btrfs_workers endio_meta_workers;
+	struct btrfs_workers endio_raid56_workers;
+	struct btrfs_workers rmw_workers;
 	struct btrfs_workers endio_meta_write_workers;
 	struct btrfs_workers endio_write_workers;
 	struct btrfs_workers endio_freespace_worker;
@@ -3490,9 +3528,9 @@
 		     struct writeback_control *wbc);
 int btrfs_create_subvol_root(struct btrfs_trans_handle *trans,
 			     struct btrfs_root *new_root, u64 new_dirid);
-int btrfs_merge_bio_hook(struct page *page, unsigned long offset,
-			 size_t size, struct bio *bio, unsigned long bio_flags);
-
+int btrfs_merge_bio_hook(int rw, struct page *page, unsigned long offset,
+			 size_t size, struct bio *bio,
+			 unsigned long bio_flags);
 int btrfs_page_mkwrite(struct vm_area_struct *vma, struct vm_fault *vmf);
 int btrfs_readpage(struct file *file, struct page *page);
 void btrfs_evict_inode(struct inode *inode);
diff --git a/fs/btrfs/delayed-ref.h b/fs/btrfs/delayed-ref.h
index 7939149..f75fcaf 100644
--- a/fs/btrfs/delayed-ref.h
+++ b/fs/btrfs/delayed-ref.h
@@ -132,6 +132,15 @@
 	unsigned long num_heads_ready;
 
 	/*
+	 * bumped when someone is making progress on the delayed
+	 * refs, so that other procs know they are just adding to
+	 * contention intead of helping
+	 */
+	atomic_t procs_running_refs;
+	atomic_t ref_seq;
+	wait_queue_head_t wait;
+
+	/*
 	 * set when the tree is flushing before a transaction commit,
 	 * used by the throttling code to decide if new updates need
 	 * to be run right away
diff --git a/fs/btrfs/disk-io.c b/fs/btrfs/disk-io.c
index 779b401..eb7c143 100644
--- a/fs/btrfs/disk-io.c
+++ b/fs/btrfs/disk-io.c
@@ -46,6 +46,7 @@
 #include "check-integrity.h"
 #include "rcu-string.h"
 #include "dev-replace.h"
+#include "raid56.h"
 
 #ifdef CONFIG_X86
 #include <asm/cpufeature.h>
@@ -640,8 +641,15 @@
 		btree_readahead_hook(root, eb, eb->start, ret);
 	}
 
-	if (ret)
+	if (ret) {
+		/*
+		 * our io error hook is going to dec the io pages
+		 * again, we have to make sure it has something
+		 * to decrement
+		 */
+		atomic_inc(&eb->io_pages);
 		clear_extent_buffer_uptodate(eb);
+	}
 	free_extent_buffer(eb);
 out:
 	return ret;
@@ -655,6 +663,7 @@
 	eb = (struct extent_buffer *)page->private;
 	set_bit(EXTENT_BUFFER_IOERR, &eb->bflags);
 	eb->read_mirror = failed_mirror;
+	atomic_dec(&eb->io_pages);
 	if (test_and_clear_bit(EXTENT_BUFFER_READAHEAD, &eb->bflags))
 		btree_readahead_hook(root, eb, eb->start, -EIO);
 	return -EIO;	/* we fixed nothing */
@@ -671,17 +680,23 @@
 	end_io_wq->work.flags = 0;
 
 	if (bio->bi_rw & REQ_WRITE) {
-		if (end_io_wq->metadata == 1)
+		if (end_io_wq->metadata == BTRFS_WQ_ENDIO_METADATA)
 			btrfs_queue_worker(&fs_info->endio_meta_write_workers,
 					   &end_io_wq->work);
-		else if (end_io_wq->metadata == 2)
+		else if (end_io_wq->metadata == BTRFS_WQ_ENDIO_FREE_SPACE)
 			btrfs_queue_worker(&fs_info->endio_freespace_worker,
 					   &end_io_wq->work);
+		else if (end_io_wq->metadata == BTRFS_WQ_ENDIO_RAID56)
+			btrfs_queue_worker(&fs_info->endio_raid56_workers,
+					   &end_io_wq->work);
 		else
 			btrfs_queue_worker(&fs_info->endio_write_workers,
 					   &end_io_wq->work);
 	} else {
-		if (end_io_wq->metadata)
+		if (end_io_wq->metadata == BTRFS_WQ_ENDIO_RAID56)
+			btrfs_queue_worker(&fs_info->endio_raid56_workers,
+					   &end_io_wq->work);
+		else if (end_io_wq->metadata)
 			btrfs_queue_worker(&fs_info->endio_meta_workers,
 					   &end_io_wq->work);
 		else
@@ -696,6 +711,7 @@
  * 0 - if data
  * 1 - if normal metadta
  * 2 - if writing to the free space cache area
+ * 3 - raid parity work
  */
 int btrfs_bio_wq_end_io(struct btrfs_fs_info *info, struct bio *bio,
 			int metadata)
@@ -2179,6 +2195,12 @@
 	init_waitqueue_head(&fs_info->transaction_blocked_wait);
 	init_waitqueue_head(&fs_info->async_submit_wait);
 
+	ret = btrfs_alloc_stripe_hash_table(fs_info);
+	if (ret) {
+		err = -ENOMEM;
+		goto fail_alloc;
+	}
+
 	__setup_root(4096, 4096, 4096, 4096, tree_root,
 		     fs_info, BTRFS_ROOT_TREE_OBJECTID);
 
@@ -2349,6 +2371,12 @@
 	btrfs_init_workers(&fs_info->endio_meta_write_workers,
 			   "endio-meta-write", fs_info->thread_pool_size,
 			   &fs_info->generic_worker);
+	btrfs_init_workers(&fs_info->endio_raid56_workers,
+			   "endio-raid56", fs_info->thread_pool_size,
+			   &fs_info->generic_worker);
+	btrfs_init_workers(&fs_info->rmw_workers,
+			   "rmw", fs_info->thread_pool_size,
+			   &fs_info->generic_worker);
 	btrfs_init_workers(&fs_info->endio_write_workers, "endio-write",
 			   fs_info->thread_pool_size,
 			   &fs_info->generic_worker);
@@ -2367,6 +2395,8 @@
 	 */
 	fs_info->endio_workers.idle_thresh = 4;
 	fs_info->endio_meta_workers.idle_thresh = 4;
+	fs_info->endio_raid56_workers.idle_thresh = 4;
+	fs_info->rmw_workers.idle_thresh = 2;
 
 	fs_info->endio_write_workers.idle_thresh = 2;
 	fs_info->endio_meta_write_workers.idle_thresh = 2;
@@ -2383,6 +2413,8 @@
 	ret |= btrfs_start_workers(&fs_info->fixup_workers);
 	ret |= btrfs_start_workers(&fs_info->endio_workers);
 	ret |= btrfs_start_workers(&fs_info->endio_meta_workers);
+	ret |= btrfs_start_workers(&fs_info->rmw_workers);
+	ret |= btrfs_start_workers(&fs_info->endio_raid56_workers);
 	ret |= btrfs_start_workers(&fs_info->endio_meta_write_workers);
 	ret |= btrfs_start_workers(&fs_info->endio_write_workers);
 	ret |= btrfs_start_workers(&fs_info->endio_freespace_worker);
@@ -2726,6 +2758,8 @@
 	btrfs_stop_workers(&fs_info->workers);
 	btrfs_stop_workers(&fs_info->endio_workers);
 	btrfs_stop_workers(&fs_info->endio_meta_workers);
+	btrfs_stop_workers(&fs_info->endio_raid56_workers);
+	btrfs_stop_workers(&fs_info->rmw_workers);
 	btrfs_stop_workers(&fs_info->endio_meta_write_workers);
 	btrfs_stop_workers(&fs_info->endio_write_workers);
 	btrfs_stop_workers(&fs_info->endio_freespace_worker);
@@ -2747,6 +2781,7 @@
 fail_srcu:
 	cleanup_srcu_struct(&fs_info->subvol_srcu);
 fail:
+	btrfs_free_stripe_hash_table(fs_info);
 	btrfs_close_devices(fs_info->fs_devices);
 	return err;
 
@@ -3094,11 +3129,16 @@
 				     ((flags & BTRFS_BLOCK_GROUP_PROFILE_MASK)
 				      == 0)))
 					num_tolerated_disk_barrier_failures = 0;
-				else if (num_tolerated_disk_barrier_failures > 1
-					 &&
-					 (flags & (BTRFS_BLOCK_GROUP_RAID1 |
-						   BTRFS_BLOCK_GROUP_RAID10)))
-					num_tolerated_disk_barrier_failures = 1;
+				else if (num_tolerated_disk_barrier_failures > 1) {
+					if (flags & (BTRFS_BLOCK_GROUP_RAID1 |
+					    BTRFS_BLOCK_GROUP_RAID5 |
+					    BTRFS_BLOCK_GROUP_RAID10)) {
+						num_tolerated_disk_barrier_failures = 1;
+					} else if (flags &
+						   BTRFS_BLOCK_GROUP_RAID5) {
+						num_tolerated_disk_barrier_failures = 2;
+					}
+				}
 			}
 		}
 		up_read(&sinfo->groups_sem);
@@ -3402,6 +3442,8 @@
 	btrfs_stop_workers(&fs_info->workers);
 	btrfs_stop_workers(&fs_info->endio_workers);
 	btrfs_stop_workers(&fs_info->endio_meta_workers);
+	btrfs_stop_workers(&fs_info->endio_raid56_workers);
+	btrfs_stop_workers(&fs_info->rmw_workers);
 	btrfs_stop_workers(&fs_info->endio_meta_write_workers);
 	btrfs_stop_workers(&fs_info->endio_write_workers);
 	btrfs_stop_workers(&fs_info->endio_freespace_worker);
@@ -3424,6 +3466,8 @@
 	bdi_destroy(&fs_info->bdi);
 	cleanup_srcu_struct(&fs_info->subvol_srcu);
 
+	btrfs_free_stripe_hash_table(fs_info);
+
 	return 0;
 }
 
diff --git a/fs/btrfs/disk-io.h b/fs/btrfs/disk-io.h
index 305c33e..034d7dc 100644
--- a/fs/btrfs/disk-io.h
+++ b/fs/btrfs/disk-io.h
@@ -25,6 +25,13 @@
 #define BTRFS_SUPER_MIRROR_MAX	 3
 #define BTRFS_SUPER_MIRROR_SHIFT 12
 
+enum {
+	BTRFS_WQ_ENDIO_DATA = 0,
+	BTRFS_WQ_ENDIO_METADATA = 1,
+	BTRFS_WQ_ENDIO_FREE_SPACE = 2,
+	BTRFS_WQ_ENDIO_RAID56 = 3,
+};
+
 static inline u64 btrfs_sb_offset(int mirror)
 {
 	u64 start = 16 * 1024;
diff --git a/fs/btrfs/extent-tree.c b/fs/btrfs/extent-tree.c
index 5cd44e2..b3ecca4 100644
--- a/fs/btrfs/extent-tree.c
+++ b/fs/btrfs/extent-tree.c
@@ -31,6 +31,7 @@
 #include "print-tree.h"
 #include "transaction.h"
 #include "volumes.h"
+#include "raid56.h"
 #include "locking.h"
 #include "free-space-cache.h"
 #include "math.h"
@@ -1852,6 +1853,8 @@
 		*actual_bytes = discarded_bytes;
 
 
+	if (ret == -EOPNOTSUPP)
+		ret = 0;
 	return ret;
 }
 
@@ -2440,6 +2443,16 @@
 	return ret;
 }
 
+static int refs_newer(struct btrfs_delayed_ref_root *delayed_refs, int seq,
+		      int count)
+{
+	int val = atomic_read(&delayed_refs->ref_seq);
+
+	if (val < seq || val >= seq + count)
+		return 1;
+	return 0;
+}
+
 /*
  * this starts processing the delayed reference count updates and
  * extent insertions we have queued up so far.  count can be
@@ -2474,6 +2487,44 @@
 
 	delayed_refs = &trans->transaction->delayed_refs;
 	INIT_LIST_HEAD(&cluster);
+	if (count == 0) {
+		count = delayed_refs->num_entries * 2;
+		run_most = 1;
+	}
+
+	if (!run_all && !run_most) {
+		int old;
+		int seq = atomic_read(&delayed_refs->ref_seq);
+
+progress:
+		old = atomic_cmpxchg(&delayed_refs->procs_running_refs, 0, 1);
+		if (old) {
+			DEFINE_WAIT(__wait);
+			if (delayed_refs->num_entries < 16348)
+				return 0;
+
+			prepare_to_wait(&delayed_refs->wait, &__wait,
+					TASK_UNINTERRUPTIBLE);
+
+			old = atomic_cmpxchg(&delayed_refs->procs_running_refs, 0, 1);
+			if (old) {
+				schedule();
+				finish_wait(&delayed_refs->wait, &__wait);
+
+				if (!refs_newer(delayed_refs, seq, 256))
+					goto progress;
+				else
+					return 0;
+			} else {
+				finish_wait(&delayed_refs->wait, &__wait);
+				goto again;
+			}
+		}
+
+	} else {
+		atomic_inc(&delayed_refs->procs_running_refs);
+	}
+
 again:
 	loops = 0;
 	spin_lock(&delayed_refs->lock);
@@ -2482,10 +2533,6 @@
 	delayed_refs->run_delayed_start = find_middle(&delayed_refs->root);
 #endif
 
-	if (count == 0) {
-		count = delayed_refs->num_entries * 2;
-		run_most = 1;
-	}
 	while (1) {
 		if (!(run_all || run_most) &&
 		    delayed_refs->num_heads_ready < 64)
@@ -2508,9 +2555,12 @@
 			btrfs_release_ref_cluster(&cluster);
 			spin_unlock(&delayed_refs->lock);
 			btrfs_abort_transaction(trans, root, ret);
+			atomic_dec(&delayed_refs->procs_running_refs);
 			return ret;
 		}
 
+		atomic_add(ret, &delayed_refs->ref_seq);
+
 		count -= min_t(unsigned long, ret, count);
 
 		if (count == 0)
@@ -2579,6 +2629,11 @@
 		goto again;
 	}
 out:
+	atomic_dec(&delayed_refs->procs_running_refs);
+	smp_mb();
+	if (waitqueue_active(&delayed_refs->wait))
+		wake_up(&delayed_refs->wait);
+
 	spin_unlock(&delayed_refs->lock);
 	assert_qgroups_uptodate(trans);
 	return 0;
@@ -3284,6 +3339,7 @@
 	u64 num_devices = root->fs_info->fs_devices->rw_devices +
 		root->fs_info->fs_devices->missing_devices;
 	u64 target;
+	u64 tmp;
 
 	/*
 	 * see if restripe for this chunk_type is in progress, if so
@@ -3300,30 +3356,32 @@
 	}
 	spin_unlock(&root->fs_info->balance_lock);
 
+	/* First, mask out the RAID levels which aren't possible */
 	if (num_devices == 1)
-		flags &= ~(BTRFS_BLOCK_GROUP_RAID1 | BTRFS_BLOCK_GROUP_RAID0);
+		flags &= ~(BTRFS_BLOCK_GROUP_RAID1 | BTRFS_BLOCK_GROUP_RAID0 |
+			   BTRFS_BLOCK_GROUP_RAID5);
+	if (num_devices < 3)
+		flags &= ~BTRFS_BLOCK_GROUP_RAID6;
 	if (num_devices < 4)
 		flags &= ~BTRFS_BLOCK_GROUP_RAID10;
 
-	if ((flags & BTRFS_BLOCK_GROUP_DUP) &&
-	    (flags & (BTRFS_BLOCK_GROUP_RAID1 |
-		      BTRFS_BLOCK_GROUP_RAID10))) {
-		flags &= ~BTRFS_BLOCK_GROUP_DUP;
-	}
+	tmp = flags & (BTRFS_BLOCK_GROUP_DUP | BTRFS_BLOCK_GROUP_RAID0 |
+		       BTRFS_BLOCK_GROUP_RAID1 | BTRFS_BLOCK_GROUP_RAID5 |
+		       BTRFS_BLOCK_GROUP_RAID6 | BTRFS_BLOCK_GROUP_RAID10);
+	flags &= ~tmp;
 
-	if ((flags & BTRFS_BLOCK_GROUP_RAID1) &&
-	    (flags & BTRFS_BLOCK_GROUP_RAID10)) {
-		flags &= ~BTRFS_BLOCK_GROUP_RAID1;
-	}
+	if (tmp & BTRFS_BLOCK_GROUP_RAID6)
+		tmp = BTRFS_BLOCK_GROUP_RAID6;
+	else if (tmp & BTRFS_BLOCK_GROUP_RAID5)
+		tmp = BTRFS_BLOCK_GROUP_RAID5;
+	else if (tmp & BTRFS_BLOCK_GROUP_RAID10)
+		tmp = BTRFS_BLOCK_GROUP_RAID10;
+	else if (tmp & BTRFS_BLOCK_GROUP_RAID1)
+		tmp = BTRFS_BLOCK_GROUP_RAID1;
+	else if (tmp & BTRFS_BLOCK_GROUP_RAID0)
+		tmp = BTRFS_BLOCK_GROUP_RAID0;
 
-	if ((flags & BTRFS_BLOCK_GROUP_RAID0) &&
-	    ((flags & BTRFS_BLOCK_GROUP_RAID1) |
-	     (flags & BTRFS_BLOCK_GROUP_RAID10) |
-	     (flags & BTRFS_BLOCK_GROUP_DUP))) {
-		flags &= ~BTRFS_BLOCK_GROUP_RAID0;
-	}
-
-	return extended_to_chunk(flags);
+	return extended_to_chunk(flags | tmp);
 }
 
 static u64 get_alloc_profile(struct btrfs_root *root, u64 flags)
@@ -3347,6 +3405,7 @@
 u64 btrfs_get_alloc_profile(struct btrfs_root *root, int data)
 {
 	u64 flags;
+	u64 ret;
 
 	if (data)
 		flags = BTRFS_BLOCK_GROUP_DATA;
@@ -3355,7 +3414,8 @@
 	else
 		flags = BTRFS_BLOCK_GROUP_METADATA;
 
-	return get_alloc_profile(root, flags);
+	ret = get_alloc_profile(root, flags);
+	return ret;
 }
 
 /*
@@ -3530,8 +3590,10 @@
 {
 	u64 num_dev;
 
-	if (type & BTRFS_BLOCK_GROUP_RAID10 ||
-	    type & BTRFS_BLOCK_GROUP_RAID0)
+	if (type & (BTRFS_BLOCK_GROUP_RAID10 |
+		    BTRFS_BLOCK_GROUP_RAID0 |
+		    BTRFS_BLOCK_GROUP_RAID5 |
+		    BTRFS_BLOCK_GROUP_RAID6))
 		num_dev = root->fs_info->fs_devices->rw_devices;
 	else if (type & BTRFS_BLOCK_GROUP_RAID1)
 		num_dev = 2;
@@ -3706,7 +3768,9 @@
 
 	/*
 	 * If we have dup, raid1 or raid10 then only half of the free
-	 * space is actually useable.
+	 * space is actually useable.  For raid56, the space info used
+	 * doesn't include the parity drive, so we don't have to
+	 * change the math
 	 */
 	if (profile & (BTRFS_BLOCK_GROUP_DUP |
 		       BTRFS_BLOCK_GROUP_RAID1 |
@@ -5539,10 +5603,14 @@
 	return ret;
 }
 
-static u64 stripe_align(struct btrfs_root *root, u64 val)
+static u64 stripe_align(struct btrfs_root *root,
+			struct btrfs_block_group_cache *cache,
+			u64 val, u64 num_bytes)
 {
-	u64 mask = ((u64)root->stripesize - 1);
-	u64 ret = (val + mask) & ~mask;
+	u64 mask;
+	u64 ret;
+	mask = ((u64)root->stripesize - 1);
+	ret = (val + mask) & ~mask;
 	return ret;
 }
 
@@ -5599,8 +5667,12 @@
 		return BTRFS_RAID_DUP;
 	else if (flags & BTRFS_BLOCK_GROUP_RAID0)
 		return BTRFS_RAID_RAID0;
-	else
-		return BTRFS_RAID_SINGLE;
+	else if (flags & BTRFS_BLOCK_GROUP_RAID5)
+		return BTRFS_RAID_RAID5;
+	else if (flags & BTRFS_BLOCK_GROUP_RAID6)
+		return BTRFS_RAID_RAID6;
+
+	return BTRFS_RAID_SINGLE; /* BTRFS_BLOCK_GROUP_SINGLE */
 }
 
 static int get_block_group_index(struct btrfs_block_group_cache *cache)
@@ -5743,6 +5815,8 @@
 		if (!block_group_bits(block_group, data)) {
 		    u64 extra = BTRFS_BLOCK_GROUP_DUP |
 				BTRFS_BLOCK_GROUP_RAID1 |
+				BTRFS_BLOCK_GROUP_RAID5 |
+				BTRFS_BLOCK_GROUP_RAID6 |
 				BTRFS_BLOCK_GROUP_RAID10;
 
 			/*
@@ -5771,6 +5845,7 @@
 		 * lets look there
 		 */
 		if (last_ptr) {
+			unsigned long aligned_cluster;
 			/*
 			 * the refill lock keeps out other
 			 * people trying to start a new cluster
@@ -5837,11 +5912,15 @@
 				goto unclustered_alloc;
 			}
 
+			aligned_cluster = max_t(unsigned long,
+						empty_cluster + empty_size,
+					      block_group->full_stripe_len);
+
 			/* allocate a cluster in this block group */
 			ret = btrfs_find_space_cluster(trans, root,
 					       block_group, last_ptr,
 					       search_start, num_bytes,
-					       empty_cluster + empty_size);
+					       aligned_cluster);
 			if (ret == 0) {
 				/*
 				 * now pull our allocation out of this
@@ -5912,7 +5991,8 @@
 			goto loop;
 		}
 checks:
-		search_start = stripe_align(root, offset);
+		search_start = stripe_align(root, used_block_group,
+					    offset, num_bytes);
 
 		/* move on to the next group */
 		if (search_start + num_bytes >
@@ -7284,6 +7364,7 @@
 		root->fs_info->fs_devices->missing_devices;
 
 	stripped = BTRFS_BLOCK_GROUP_RAID0 |
+		BTRFS_BLOCK_GROUP_RAID5 | BTRFS_BLOCK_GROUP_RAID6 |
 		BTRFS_BLOCK_GROUP_RAID1 | BTRFS_BLOCK_GROUP_RAID10;
 
 	if (num_devices == 1) {
@@ -7837,7 +7918,9 @@
 		btrfs_release_path(path);
 		cache->flags = btrfs_block_group_flags(&cache->item);
 		cache->sectorsize = root->sectorsize;
-
+		cache->full_stripe_len = btrfs_full_stripe_len(root,
+					       &root->fs_info->mapping_tree,
+					       found_key.objectid);
 		btrfs_init_free_space_ctl(cache);
 
 		/*
@@ -7891,6 +7974,8 @@
 		if (!(get_alloc_profile(root, space_info->flags) &
 		      (BTRFS_BLOCK_GROUP_RAID10 |
 		       BTRFS_BLOCK_GROUP_RAID1 |
+		       BTRFS_BLOCK_GROUP_RAID5 |
+		       BTRFS_BLOCK_GROUP_RAID6 |
 		       BTRFS_BLOCK_GROUP_DUP)))
 			continue;
 		/*
@@ -7966,6 +8051,9 @@
 	cache->key.type = BTRFS_BLOCK_GROUP_ITEM_KEY;
 	cache->sectorsize = root->sectorsize;
 	cache->fs_info = root->fs_info;
+	cache->full_stripe_len = btrfs_full_stripe_len(root,
+					       &root->fs_info->mapping_tree,
+					       chunk_offset);
 
 	atomic_set(&cache->count, 1);
 	spin_lock_init(&cache->lock);
diff --git a/fs/btrfs/extent_io.c b/fs/btrfs/extent_io.c
index 5c00d6a..66f999b 100644
--- a/fs/btrfs/extent_io.c
+++ b/fs/btrfs/extent_io.c
@@ -1895,13 +1895,11 @@
 	if (ret)
 		err = ret;
 
-	if (did_repair) {
-		ret = clear_extent_bits(&BTRFS_I(inode)->io_tree, rec->start,
-					rec->start + rec->len - 1,
-					EXTENT_DAMAGED, GFP_NOFS);
-		if (ret && !err)
-			err = ret;
-	}
+	ret = clear_extent_bits(&BTRFS_I(inode)->io_tree, rec->start,
+				rec->start + rec->len - 1,
+				EXTENT_DAMAGED, GFP_NOFS);
+	if (ret && !err)
+		err = ret;
 
 	kfree(rec);
 	return err;
@@ -1932,10 +1930,15 @@
 	u64 map_length = 0;
 	u64 sector;
 	struct btrfs_bio *bbio = NULL;
+	struct btrfs_mapping_tree *map_tree = &fs_info->mapping_tree;
 	int ret;
 
 	BUG_ON(!mirror_num);
 
+	/* we can't repair anything in raid56 yet */
+	if (btrfs_is_parity_mirror(map_tree, logical, length, mirror_num))
+		return 0;
+
 	bio = bio_alloc(GFP_NOFS, 1);
 	if (!bio)
 		return -EIO;
@@ -2052,6 +2055,7 @@
 						failrec->failed_mirror);
 			did_repair = !ret;
 		}
+		ret = 0;
 	}
 
 out:
@@ -2487,13 +2491,13 @@
 	return ret;
 }
 
-static int merge_bio(struct extent_io_tree *tree, struct page *page,
+static int merge_bio(int rw, struct extent_io_tree *tree, struct page *page,
 		     unsigned long offset, size_t size, struct bio *bio,
 		     unsigned long bio_flags)
 {
 	int ret = 0;
 	if (tree->ops && tree->ops->merge_bio_hook)
-		ret = tree->ops->merge_bio_hook(page, offset, size, bio,
+		ret = tree->ops->merge_bio_hook(rw, page, offset, size, bio,
 						bio_flags);
 	BUG_ON(ret < 0);
 	return ret;
@@ -2528,7 +2532,7 @@
 				sector;
 
 		if (prev_bio_flags != bio_flags || !contig ||
-		    merge_bio(tree, page, offset, page_size, bio, bio_flags) ||
+		    merge_bio(rw, tree, page, offset, page_size, bio, bio_flags) ||
 		    bio_add_page(bio, page, page_size, offset) < page_size) {
 			ret = submit_one_bio(rw, bio, mirror_num,
 					     prev_bio_flags);
@@ -4162,6 +4166,7 @@
 
 static void check_buffer_tree_ref(struct extent_buffer *eb)
 {
+	int refs;
 	/* the ref bit is tricky.  We have to make sure it is set
 	 * if we have the buffer dirty.   Otherwise the
 	 * code to free a buffer can end up dropping a dirty
@@ -4182,6 +4187,10 @@
 	 * So bump the ref count first, then set the bit.  If someone
 	 * beat us to it, drop the ref we added.
 	 */
+	refs = atomic_read(&eb->refs);
+	if (refs >= 2 && test_bit(EXTENT_BUFFER_TREE_REF, &eb->bflags))
+		return;
+
 	spin_lock(&eb->refs_lock);
 	if (!test_and_set_bit(EXTENT_BUFFER_TREE_REF, &eb->bflags))
 		atomic_inc(&eb->refs);
@@ -4383,9 +4392,20 @@
 
 void free_extent_buffer(struct extent_buffer *eb)
 {
+	int refs;
+	int old;
 	if (!eb)
 		return;
 
+	while (1) {
+		refs = atomic_read(&eb->refs);
+		if (refs <= 3)
+			break;
+		old = atomic_cmpxchg(&eb->refs, refs, refs - 1);
+		if (old == refs)
+			return;
+	}
+
 	spin_lock(&eb->refs_lock);
 	if (atomic_read(&eb->refs) == 2 &&
 	    test_bit(EXTENT_BUFFER_DUMMY, &eb->bflags))
diff --git a/fs/btrfs/extent_io.h b/fs/btrfs/extent_io.h
index ff18232..dc81868 100644
--- a/fs/btrfs/extent_io.h
+++ b/fs/btrfs/extent_io.h
@@ -72,7 +72,7 @@
 	int (*writepage_start_hook)(struct page *page, u64 start, u64 end);
 	int (*writepage_io_hook)(struct page *page, u64 start, u64 end);
 	extent_submit_bio_hook_t *submit_bio_hook;
-	int (*merge_bio_hook)(struct page *page, unsigned long offset,
+	int (*merge_bio_hook)(int rw, struct page *page, unsigned long offset,
 			      size_t size, struct bio *bio,
 			      unsigned long bio_flags);
 	int (*readpage_io_failed_hook)(struct page *page, int failed_mirror);
diff --git a/fs/btrfs/free-space-cache.c b/fs/btrfs/free-space-cache.c
index c8090f1..1f84fc0 100644
--- a/fs/btrfs/free-space-cache.c
+++ b/fs/btrfs/free-space-cache.c
@@ -1465,10 +1465,14 @@
 }
 
 static struct btrfs_free_space *
-find_free_space(struct btrfs_free_space_ctl *ctl, u64 *offset, u64 *bytes)
+find_free_space(struct btrfs_free_space_ctl *ctl, u64 *offset, u64 *bytes,
+		unsigned long align)
 {
 	struct btrfs_free_space *entry;
 	struct rb_node *node;
+	u64 ctl_off;
+	u64 tmp;
+	u64 align_off;
 	int ret;
 
 	if (!ctl->free_space_offset.rb_node)
@@ -1483,15 +1487,34 @@
 		if (entry->bytes < *bytes)
 			continue;
 
+		/* make sure the space returned is big enough
+		 * to match our requested alignment
+		 */
+		if (*bytes >= align) {
+			ctl_off = entry->offset - ctl->start;
+			tmp = ctl_off + align - 1;;
+			do_div(tmp, align);
+			tmp = tmp * align + ctl->start;
+			align_off = tmp - entry->offset;
+		} else {
+			align_off = 0;
+			tmp = entry->offset;
+		}
+
+		if (entry->bytes < *bytes + align_off)
+			continue;
+
 		if (entry->bitmap) {
-			ret = search_bitmap(ctl, entry, offset, bytes);
-			if (!ret)
+			ret = search_bitmap(ctl, entry, &tmp, bytes);
+			if (!ret) {
+				*offset = tmp;
 				return entry;
+			}
 			continue;
 		}
 
-		*offset = entry->offset;
-		*bytes = entry->bytes;
+		*offset = tmp;
+		*bytes = entry->bytes - align_off;
 		return entry;
 	}
 
@@ -2101,9 +2124,12 @@
 	struct btrfs_free_space *entry = NULL;
 	u64 bytes_search = bytes + empty_size;
 	u64 ret = 0;
+	u64 align_gap = 0;
+	u64 align_gap_len = 0;
 
 	spin_lock(&ctl->tree_lock);
-	entry = find_free_space(ctl, &offset, &bytes_search);
+	entry = find_free_space(ctl, &offset, &bytes_search,
+				block_group->full_stripe_len);
 	if (!entry)
 		goto out;
 
@@ -2113,9 +2139,15 @@
 		if (!entry->bytes)
 			free_bitmap(ctl, entry);
 	} else {
+
 		unlink_free_space(ctl, entry);
-		entry->offset += bytes;
-		entry->bytes -= bytes;
+		align_gap_len = offset - entry->offset;
+		align_gap = entry->offset;
+
+		entry->offset = offset + bytes;
+		WARN_ON(entry->bytes < bytes + align_gap_len);
+
+		entry->bytes -= bytes + align_gap_len;
 		if (!entry->bytes)
 			kmem_cache_free(btrfs_free_space_cachep, entry);
 		else
@@ -2125,6 +2157,8 @@
 out:
 	spin_unlock(&ctl->tree_lock);
 
+	if (align_gap_len)
+		__btrfs_add_free_space(ctl, align_gap, align_gap_len);
 	return ret;
 }
 
diff --git a/fs/btrfs/inode.c b/fs/btrfs/inode.c
index 1aa98be..4e6a11c 100644
--- a/fs/btrfs/inode.c
+++ b/fs/btrfs/inode.c
@@ -40,6 +40,7 @@
 #include <linux/ratelimit.h>
 #include <linux/mount.h>
 #include <linux/btrfs.h>
+#include <linux/blkdev.h>
 #include "compat.h"
 #include "ctree.h"
 #include "disk-io.h"
@@ -1605,7 +1606,7 @@
  * extent_io.c merge_bio_hook, this must check the chunk tree to make sure
  * we don't create bios that span stripes or chunks
  */
-int btrfs_merge_bio_hook(struct page *page, unsigned long offset,
+int btrfs_merge_bio_hook(int rw, struct page *page, unsigned long offset,
 			 size_t size, struct bio *bio,
 			 unsigned long bio_flags)
 {
@@ -1620,7 +1621,7 @@
 
 	length = bio->bi_size;
 	map_length = length;
-	ret = btrfs_map_block(root->fs_info, READ, logical,
+	ret = btrfs_map_block(root->fs_info, rw, logical,
 			      &map_length, NULL, 0);
 	/* Will always return 0 with map_multi == NULL */
 	BUG_ON(ret < 0);
@@ -6464,19 +6465,24 @@
 	int async_submit = 0;
 
 	map_length = orig_bio->bi_size;
-	ret = btrfs_map_block(root->fs_info, READ, start_sector << 9,
+	ret = btrfs_map_block(root->fs_info, rw, start_sector << 9,
 			      &map_length, NULL, 0);
 	if (ret) {
 		bio_put(orig_bio);
 		return -EIO;
 	}
-
 	if (map_length >= orig_bio->bi_size) {
 		bio = orig_bio;
 		goto submit;
 	}
 
-	async_submit = 1;
+	/* async crcs make it difficult to collect full stripe writes. */
+	if (btrfs_get_alloc_profile(root, 1) &
+	    (BTRFS_BLOCK_GROUP_RAID5 | BTRFS_BLOCK_GROUP_RAID6))
+		async_submit = 0;
+	else
+		async_submit = 1;
+
 	bio = btrfs_dio_bio_alloc(orig_bio->bi_bdev, start_sector, GFP_NOFS);
 	if (!bio)
 		return -ENOMEM;
@@ -6518,7 +6524,7 @@
 			bio->bi_end_io = btrfs_end_dio_bio;
 
 			map_length = orig_bio->bi_size;
-			ret = btrfs_map_block(root->fs_info, READ,
+			ret = btrfs_map_block(root->fs_info, rw,
 					      start_sector << 9,
 					      &map_length, NULL, 0);
 			if (ret) {
diff --git a/fs/btrfs/raid56.c b/fs/btrfs/raid56.c
new file mode 100644
index 0000000..e34e568
--- /dev/null
+++ b/fs/btrfs/raid56.c
@@ -0,0 +1,2080 @@
+/*
+ * Copyright (C) 2012 Fusion-io  All rights reserved.
+ * Copyright (C) 2012 Intel Corp. All rights reserved.
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public
+ * License v2 as published by the Free Software Foundation.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public
+ * License along with this program; if not, write to the
+ * Free Software Foundation, Inc., 59 Temple Place - Suite 330,
+ * Boston, MA 021110-1307, USA.
+ */
+#include <linux/sched.h>
+#include <linux/wait.h>
+#include <linux/bio.h>
+#include <linux/slab.h>
+#include <linux/buffer_head.h>
+#include <linux/blkdev.h>
+#include <linux/random.h>
+#include <linux/iocontext.h>
+#include <linux/capability.h>
+#include <linux/ratelimit.h>
+#include <linux/kthread.h>
+#include <linux/raid/pq.h>
+#include <linux/hash.h>
+#include <linux/list_sort.h>
+#include <linux/raid/xor.h>
+#include <asm/div64.h>
+#include "compat.h"
+#include "ctree.h"
+#include "extent_map.h"
+#include "disk-io.h"
+#include "transaction.h"
+#include "print-tree.h"
+#include "volumes.h"
+#include "raid56.h"
+#include "async-thread.h"
+#include "check-integrity.h"
+#include "rcu-string.h"
+
+/* set when additional merges to this rbio are not allowed */
+#define RBIO_RMW_LOCKED_BIT	1
+
+/*
+ * set when this rbio is sitting in the hash, but it is just a cache
+ * of past RMW
+ */
+#define RBIO_CACHE_BIT		2
+
+/*
+ * set when it is safe to trust the stripe_pages for caching
+ */
+#define RBIO_CACHE_READY_BIT	3
+
+
+#define RBIO_CACHE_SIZE 1024
+
+struct btrfs_raid_bio {
+	struct btrfs_fs_info *fs_info;
+	struct btrfs_bio *bbio;
+
+	/*
+	 * logical block numbers for the start of each stripe
+	 * The last one or two are p/q.  These are sorted,
+	 * so raid_map[0] is the start of our full stripe
+	 */
+	u64 *raid_map;
+
+	/* while we're doing rmw on a stripe
+	 * we put it into a hash table so we can
+	 * lock the stripe and merge more rbios
+	 * into it.
+	 */
+	struct list_head hash_list;
+
+	/*
+	 * LRU list for the stripe cache
+	 */
+	struct list_head stripe_cache;
+
+	/*
+	 * for scheduling work in the helper threads
+	 */
+	struct btrfs_work work;
+
+	/*
+	 * bio list and bio_list_lock are used
+	 * to add more bios into the stripe
+	 * in hopes of avoiding the full rmw
+	 */
+	struct bio_list bio_list;
+	spinlock_t bio_list_lock;
+
+	/* also protected by the bio_list_lock, the
+	 * plug list is used by the plugging code
+	 * to collect partial bios while plugged.  The
+	 * stripe locking code also uses it to hand off
+	 * the stripe lock to the next pending IO
+	 */
+	struct list_head plug_list;
+
+	/*
+	 * flags that tell us if it is safe to
+	 * merge with this bio
+	 */
+	unsigned long flags;
+
+	/* size of each individual stripe on disk */
+	int stripe_len;
+
+	/* number of data stripes (no p/q) */
+	int nr_data;
+
+	/*
+	 * set if we're doing a parity rebuild
+	 * for a read from higher up, which is handled
+	 * differently from a parity rebuild as part of
+	 * rmw
+	 */
+	int read_rebuild;
+
+	/* first bad stripe */
+	int faila;
+
+	/* second bad stripe (for raid6 use) */
+	int failb;
+
+	/*
+	 * number of pages needed to represent the full
+	 * stripe
+	 */
+	int nr_pages;
+
+	/*
+	 * size of all the bios in the bio_list.  This
+	 * helps us decide if the rbio maps to a full
+	 * stripe or not
+	 */
+	int bio_list_bytes;
+
+	atomic_t refs;
+
+	/*
+	 * these are two arrays of pointers.  We allocate the
+	 * rbio big enough to hold them both and setup their
+	 * locations when the rbio is allocated
+	 */
+
+	/* pointers to pages that we allocated for
+	 * reading/writing stripes directly from the disk (including P/Q)
+	 */
+	struct page **stripe_pages;
+
+	/*
+	 * pointers to the pages in the bio_list.  Stored
+	 * here for faster lookup
+	 */
+	struct page **bio_pages;
+};
+
+static int __raid56_parity_recover(struct btrfs_raid_bio *rbio);
+static noinline void finish_rmw(struct btrfs_raid_bio *rbio);
+static void rmw_work(struct btrfs_work *work);
+static void read_rebuild_work(struct btrfs_work *work);
+static void async_rmw_stripe(struct btrfs_raid_bio *rbio);
+static void async_read_rebuild(struct btrfs_raid_bio *rbio);
+static int fail_bio_stripe(struct btrfs_raid_bio *rbio, struct bio *bio);
+static int fail_rbio_index(struct btrfs_raid_bio *rbio, int failed);
+static void __free_raid_bio(struct btrfs_raid_bio *rbio);
+static void index_rbio_pages(struct btrfs_raid_bio *rbio);
+static int alloc_rbio_pages(struct btrfs_raid_bio *rbio);
+
+/*
+ * the stripe hash table is used for locking, and to collect
+ * bios in hopes of making a full stripe
+ */
+int btrfs_alloc_stripe_hash_table(struct btrfs_fs_info *info)
+{
+	struct btrfs_stripe_hash_table *table;
+	struct btrfs_stripe_hash_table *x;
+	struct btrfs_stripe_hash *cur;
+	struct btrfs_stripe_hash *h;
+	int num_entries = 1 << BTRFS_STRIPE_HASH_TABLE_BITS;
+	int i;
+
+	if (info->stripe_hash_table)
+		return 0;
+
+	table = kzalloc(sizeof(*table) + sizeof(*h) * num_entries, GFP_NOFS);
+	if (!table)
+		return -ENOMEM;
+
+	spin_lock_init(&table->cache_lock);
+	INIT_LIST_HEAD(&table->stripe_cache);
+
+	h = table->table;
+
+	for (i = 0; i < num_entries; i++) {
+		cur = h + i;
+		INIT_LIST_HEAD(&cur->hash_list);
+		spin_lock_init(&cur->lock);
+		init_waitqueue_head(&cur->wait);
+	}
+
+	x = cmpxchg(&info->stripe_hash_table, NULL, table);
+	if (x)
+		kfree(x);
+	return 0;
+}
+
+/*
+ * caching an rbio means to copy anything from the
+ * bio_pages array into the stripe_pages array.  We
+ * use the page uptodate bit in the stripe cache array
+ * to indicate if it has valid data
+ *
+ * once the caching is done, we set the cache ready
+ * bit.
+ */
+static void cache_rbio_pages(struct btrfs_raid_bio *rbio)
+{
+	int i;
+	char *s;
+	char *d;
+	int ret;
+
+	ret = alloc_rbio_pages(rbio);
+	if (ret)
+		return;
+
+	for (i = 0; i < rbio->nr_pages; i++) {
+		if (!rbio->bio_pages[i])
+			continue;
+
+		s = kmap(rbio->bio_pages[i]);
+		d = kmap(rbio->stripe_pages[i]);
+
+		memcpy(d, s, PAGE_CACHE_SIZE);
+
+		kunmap(rbio->bio_pages[i]);
+		kunmap(rbio->stripe_pages[i]);
+		SetPageUptodate(rbio->stripe_pages[i]);
+	}
+	set_bit(RBIO_CACHE_READY_BIT, &rbio->flags);
+}
+
+/*
+ * we hash on the first logical address of the stripe
+ */
+static int rbio_bucket(struct btrfs_raid_bio *rbio)
+{
+	u64 num = rbio->raid_map[0];
+
+	/*
+	 * we shift down quite a bit.  We're using byte
+	 * addressing, and most of the lower bits are zeros.
+	 * This tends to upset hash_64, and it consistently
+	 * returns just one or two different values.
+	 *
+	 * shifting off the lower bits fixes things.
+	 */
+	return hash_64(num >> 16, BTRFS_STRIPE_HASH_TABLE_BITS);
+}
+
+/*
+ * stealing an rbio means taking all the uptodate pages from the stripe
+ * array in the source rbio and putting them into the destination rbio
+ */
+static void steal_rbio(struct btrfs_raid_bio *src, struct btrfs_raid_bio *dest)
+{
+	int i;
+	struct page *s;
+	struct page *d;
+
+	if (!test_bit(RBIO_CACHE_READY_BIT, &src->flags))
+		return;
+
+	for (i = 0; i < dest->nr_pages; i++) {
+		s = src->stripe_pages[i];
+		if (!s || !PageUptodate(s)) {
+			continue;
+		}
+
+		d = dest->stripe_pages[i];
+		if (d)
+			__free_page(d);
+
+		dest->stripe_pages[i] = s;
+		src->stripe_pages[i] = NULL;
+	}
+}
+
+/*
+ * merging means we take the bio_list from the victim and
+ * splice it into the destination.  The victim should
+ * be discarded afterwards.
+ *
+ * must be called with dest->rbio_list_lock held
+ */
+static void merge_rbio(struct btrfs_raid_bio *dest,
+		       struct btrfs_raid_bio *victim)
+{
+	bio_list_merge(&dest->bio_list, &victim->bio_list);
+	dest->bio_list_bytes += victim->bio_list_bytes;
+	bio_list_init(&victim->bio_list);
+}
+
+/*
+ * used to prune items that are in the cache.  The caller
+ * must hold the hash table lock.
+ */
+static void __remove_rbio_from_cache(struct btrfs_raid_bio *rbio)
+{
+	int bucket = rbio_bucket(rbio);
+	struct btrfs_stripe_hash_table *table;
+	struct btrfs_stripe_hash *h;
+	int freeit = 0;
+
+	/*
+	 * check the bit again under the hash table lock.
+	 */
+	if (!test_bit(RBIO_CACHE_BIT, &rbio->flags))
+		return;
+
+	table = rbio->fs_info->stripe_hash_table;
+	h = table->table + bucket;
+
+	/* hold the lock for the bucket because we may be
+	 * removing it from the hash table
+	 */
+	spin_lock(&h->lock);
+
+	/*
+	 * hold the lock for the bio list because we need
+	 * to make sure the bio list is empty
+	 */
+	spin_lock(&rbio->bio_list_lock);
+
+	if (test_and_clear_bit(RBIO_CACHE_BIT, &rbio->flags)) {
+		list_del_init(&rbio->stripe_cache);
+		table->cache_size -= 1;
+		freeit = 1;
+
+		/* if the bio list isn't empty, this rbio is
+		 * still involved in an IO.  We take it out
+		 * of the cache list, and drop the ref that
+		 * was held for the list.
+		 *
+		 * If the bio_list was empty, we also remove
+		 * the rbio from the hash_table, and drop
+		 * the corresponding ref
+		 */
+		if (bio_list_empty(&rbio->bio_list)) {
+			if (!list_empty(&rbio->hash_list)) {
+				list_del_init(&rbio->hash_list);
+				atomic_dec(&rbio->refs);
+				BUG_ON(!list_empty(&rbio->plug_list));
+			}
+		}
+	}
+
+	spin_unlock(&rbio->bio_list_lock);
+	spin_unlock(&h->lock);
+
+	if (freeit)
+		__free_raid_bio(rbio);
+}
+
+/*
+ * prune a given rbio from the cache
+ */
+static void remove_rbio_from_cache(struct btrfs_raid_bio *rbio)
+{
+	struct btrfs_stripe_hash_table *table;
+	unsigned long flags;
+
+	if (!test_bit(RBIO_CACHE_BIT, &rbio->flags))
+		return;
+
+	table = rbio->fs_info->stripe_hash_table;
+
+	spin_lock_irqsave(&table->cache_lock, flags);
+	__remove_rbio_from_cache(rbio);
+	spin_unlock_irqrestore(&table->cache_lock, flags);
+}
+
+/*
+ * remove everything in the cache
+ */
+void btrfs_clear_rbio_cache(struct btrfs_fs_info *info)
+{
+	struct btrfs_stripe_hash_table *table;
+	unsigned long flags;
+	struct btrfs_raid_bio *rbio;
+
+	table = info->stripe_hash_table;
+
+	spin_lock_irqsave(&table->cache_lock, flags);
+	while (!list_empty(&table->stripe_cache)) {
+		rbio = list_entry(table->stripe_cache.next,
+				  struct btrfs_raid_bio,
+				  stripe_cache);
+		__remove_rbio_from_cache(rbio);
+	}
+	spin_unlock_irqrestore(&table->cache_lock, flags);
+}
+
+/*
+ * remove all cached entries and free the hash table
+ * used by unmount
+ */
+void btrfs_free_stripe_hash_table(struct btrfs_fs_info *info)
+{
+	if (!info->stripe_hash_table)
+		return;
+	btrfs_clear_rbio_cache(info);
+	kfree(info->stripe_hash_table);
+	info->stripe_hash_table = NULL;
+}
+
+/*
+ * insert an rbio into the stripe cache.  It
+ * must have already been prepared by calling
+ * cache_rbio_pages
+ *
+ * If this rbio was already cached, it gets
+ * moved to the front of the lru.
+ *
+ * If the size of the rbio cache is too big, we
+ * prune an item.
+ */
+static void cache_rbio(struct btrfs_raid_bio *rbio)
+{
+	struct btrfs_stripe_hash_table *table;
+	unsigned long flags;
+
+	if (!test_bit(RBIO_CACHE_READY_BIT, &rbio->flags))
+		return;
+
+	table = rbio->fs_info->stripe_hash_table;
+
+	spin_lock_irqsave(&table->cache_lock, flags);
+	spin_lock(&rbio->bio_list_lock);
+
+	/* bump our ref if we were not in the list before */
+	if (!test_and_set_bit(RBIO_CACHE_BIT, &rbio->flags))
+		atomic_inc(&rbio->refs);
+
+	if (!list_empty(&rbio->stripe_cache)){
+		list_move(&rbio->stripe_cache, &table->stripe_cache);
+	} else {
+		list_add(&rbio->stripe_cache, &table->stripe_cache);
+		table->cache_size += 1;
+	}
+
+	spin_unlock(&rbio->bio_list_lock);
+
+	if (table->cache_size > RBIO_CACHE_SIZE) {
+		struct btrfs_raid_bio *found;
+
+		found = list_entry(table->stripe_cache.prev,
+				  struct btrfs_raid_bio,
+				  stripe_cache);
+
+		if (found != rbio)
+			__remove_rbio_from_cache(found);
+	}
+
+	spin_unlock_irqrestore(&table->cache_lock, flags);
+	return;
+}
+
+/*
+ * helper function to run the xor_blocks api.  It is only
+ * able to do MAX_XOR_BLOCKS at a time, so we need to
+ * loop through.
+ */
+static void run_xor(void **pages, int src_cnt, ssize_t len)
+{
+	int src_off = 0;
+	int xor_src_cnt = 0;
+	void *dest = pages[src_cnt];
+
+	while(src_cnt > 0) {
+		xor_src_cnt = min(src_cnt, MAX_XOR_BLOCKS);
+		xor_blocks(xor_src_cnt, len, dest, pages + src_off);
+
+		src_cnt -= xor_src_cnt;
+		src_off += xor_src_cnt;
+	}
+}
+
+/*
+ * returns true if the bio list inside this rbio
+ * covers an entire stripe (no rmw required).
+ * Must be called with the bio list lock held, or
+ * at a time when you know it is impossible to add
+ * new bios into the list
+ */
+static int __rbio_is_full(struct btrfs_raid_bio *rbio)
+{
+	unsigned long size = rbio->bio_list_bytes;
+	int ret = 1;
+
+	if (size != rbio->nr_data * rbio->stripe_len)
+		ret = 0;
+
+	BUG_ON(size > rbio->nr_data * rbio->stripe_len);
+	return ret;
+}
+
+static int rbio_is_full(struct btrfs_raid_bio *rbio)
+{
+	unsigned long flags;
+	int ret;
+
+	spin_lock_irqsave(&rbio->bio_list_lock, flags);
+	ret = __rbio_is_full(rbio);
+	spin_unlock_irqrestore(&rbio->bio_list_lock, flags);
+	return ret;
+}
+
+/*
+ * returns 1 if it is safe to merge two rbios together.
+ * The merging is safe if the two rbios correspond to
+ * the same stripe and if they are both going in the same
+ * direction (read vs write), and if neither one is
+ * locked for final IO
+ *
+ * The caller is responsible for locking such that
+ * rmw_locked is safe to test
+ */
+static int rbio_can_merge(struct btrfs_raid_bio *last,
+			  struct btrfs_raid_bio *cur)
+{
+	if (test_bit(RBIO_RMW_LOCKED_BIT, &last->flags) ||
+	    test_bit(RBIO_RMW_LOCKED_BIT, &cur->flags))
+		return 0;
+
+	/*
+	 * we can't merge with cached rbios, since the
+	 * idea is that when we merge the destination
+	 * rbio is going to run our IO for us.  We can
+	 * steal from cached rbio's though, other functions
+	 * handle that.
+	 */
+	if (test_bit(RBIO_CACHE_BIT, &last->flags) ||
+	    test_bit(RBIO_CACHE_BIT, &cur->flags))
+		return 0;
+
+	if (last->raid_map[0] !=
+	    cur->raid_map[0])
+		return 0;
+
+	/* reads can't merge with writes */
+	if (last->read_rebuild !=
+	    cur->read_rebuild) {
+		return 0;
+	}
+
+	return 1;
+}
+
+/*
+ * helper to index into the pstripe
+ */
+static struct page *rbio_pstripe_page(struct btrfs_raid_bio *rbio, int index)
+{
+	index += (rbio->nr_data * rbio->stripe_len) >> PAGE_CACHE_SHIFT;
+	return rbio->stripe_pages[index];
+}
+
+/*
+ * helper to index into the qstripe, returns null
+ * if there is no qstripe
+ */
+static struct page *rbio_qstripe_page(struct btrfs_raid_bio *rbio, int index)
+{
+	if (rbio->nr_data + 1 == rbio->bbio->num_stripes)
+		return NULL;
+
+	index += ((rbio->nr_data + 1) * rbio->stripe_len) >>
+		PAGE_CACHE_SHIFT;
+	return rbio->stripe_pages[index];
+}
+
+/*
+ * The first stripe in the table for a logical address
+ * has the lock.  rbios are added in one of three ways:
+ *
+ * 1) Nobody has the stripe locked yet.  The rbio is given
+ * the lock and 0 is returned.  The caller must start the IO
+ * themselves.
+ *
+ * 2) Someone has the stripe locked, but we're able to merge
+ * with the lock owner.  The rbio is freed and the IO will
+ * start automatically along with the existing rbio.  1 is returned.
+ *
+ * 3) Someone has the stripe locked, but we're not able to merge.
+ * The rbio is added to the lock owner's plug list, or merged into
+ * an rbio already on the plug list.  When the lock owner unlocks,
+ * the next rbio on the list is run and the IO is started automatically.
+ * 1 is returned
+ *
+ * If we return 0, the caller still owns the rbio and must continue with
+ * IO submission.  If we return 1, the caller must assume the rbio has
+ * already been freed.
+ */
+static noinline int lock_stripe_add(struct btrfs_raid_bio *rbio)
+{
+	int bucket = rbio_bucket(rbio);
+	struct btrfs_stripe_hash *h = rbio->fs_info->stripe_hash_table->table + bucket;
+	struct btrfs_raid_bio *cur;
+	struct btrfs_raid_bio *pending;
+	unsigned long flags;
+	DEFINE_WAIT(wait);
+	struct btrfs_raid_bio *freeit = NULL;
+	struct btrfs_raid_bio *cache_drop = NULL;
+	int ret = 0;
+	int walk = 0;
+
+	spin_lock_irqsave(&h->lock, flags);
+	list_for_each_entry(cur, &h->hash_list, hash_list) {
+		walk++;
+		if (cur->raid_map[0] == rbio->raid_map[0]) {
+			spin_lock(&cur->bio_list_lock);
+
+			/* can we steal this cached rbio's pages? */
+			if (bio_list_empty(&cur->bio_list) &&
+			    list_empty(&cur->plug_list) &&
+			    test_bit(RBIO_CACHE_BIT, &cur->flags) &&
+			    !test_bit(RBIO_RMW_LOCKED_BIT, &cur->flags)) {
+				list_del_init(&cur->hash_list);
+				atomic_dec(&cur->refs);
+
+				steal_rbio(cur, rbio);
+				cache_drop = cur;
+				spin_unlock(&cur->bio_list_lock);
+
+				goto lockit;
+			}
+
+			/* can we merge into the lock owner? */
+			if (rbio_can_merge(cur, rbio)) {
+				merge_rbio(cur, rbio);
+				spin_unlock(&cur->bio_list_lock);
+				freeit = rbio;
+				ret = 1;
+				goto out;
+			}
+
+
+			/*
+			 * we couldn't merge with the running
+			 * rbio, see if we can merge with the
+			 * pending ones.  We don't have to
+			 * check for rmw_locked because there
+			 * is no way they are inside finish_rmw
+			 * right now
+			 */
+			list_for_each_entry(pending, &cur->plug_list,
+					    plug_list) {
+				if (rbio_can_merge(pending, rbio)) {
+					merge_rbio(pending, rbio);
+					spin_unlock(&cur->bio_list_lock);
+					freeit = rbio;
+					ret = 1;
+					goto out;
+				}
+			}
+
+			/* no merging, put us on the tail of the plug list,
+			 * our rbio will be started with the currently
+			 * running rbio unlocks
+			 */
+			list_add_tail(&rbio->plug_list, &cur->plug_list);
+			spin_unlock(&cur->bio_list_lock);
+			ret = 1;
+			goto out;
+		}
+	}
+lockit:
+	atomic_inc(&rbio->refs);
+	list_add(&rbio->hash_list, &h->hash_list);
+out:
+	spin_unlock_irqrestore(&h->lock, flags);
+	if (cache_drop)
+		remove_rbio_from_cache(cache_drop);
+	if (freeit)
+		__free_raid_bio(freeit);
+	return ret;
+}
+
+/*
+ * called as rmw or parity rebuild is completed.  If the plug list has more
+ * rbios waiting for this stripe, the next one on the list will be started
+ */
+static noinline void unlock_stripe(struct btrfs_raid_bio *rbio)
+{
+	int bucket;
+	struct btrfs_stripe_hash *h;
+	unsigned long flags;
+	int keep_cache = 0;
+
+	bucket = rbio_bucket(rbio);
+	h = rbio->fs_info->stripe_hash_table->table + bucket;
+
+	if (list_empty(&rbio->plug_list))
+		cache_rbio(rbio);
+
+	spin_lock_irqsave(&h->lock, flags);
+	spin_lock(&rbio->bio_list_lock);
+
+	if (!list_empty(&rbio->hash_list)) {
+		/*
+		 * if we're still cached and there is no other IO
+		 * to perform, just leave this rbio here for others
+		 * to steal from later
+		 */
+		if (list_empty(&rbio->plug_list) &&
+		    test_bit(RBIO_CACHE_BIT, &rbio->flags)) {
+			keep_cache = 1;
+			clear_bit(RBIO_RMW_LOCKED_BIT, &rbio->flags);
+			BUG_ON(!bio_list_empty(&rbio->bio_list));
+			goto done;
+		}
+
+		list_del_init(&rbio->hash_list);
+		atomic_dec(&rbio->refs);
+
+		/*
+		 * we use the plug list to hold all the rbios
+		 * waiting for the chance to lock this stripe.
+		 * hand the lock over to one of them.
+		 */
+		if (!list_empty(&rbio->plug_list)) {
+			struct btrfs_raid_bio *next;
+			struct list_head *head = rbio->plug_list.next;
+
+			next = list_entry(head, struct btrfs_raid_bio,
+					  plug_list);
+
+			list_del_init(&rbio->plug_list);
+
+			list_add(&next->hash_list, &h->hash_list);
+			atomic_inc(&next->refs);
+			spin_unlock(&rbio->bio_list_lock);
+			spin_unlock_irqrestore(&h->lock, flags);
+
+			if (next->read_rebuild)
+				async_read_rebuild(next);
+			else {
+				steal_rbio(rbio, next);
+				async_rmw_stripe(next);
+			}
+
+			goto done_nolock;
+		} else  if (waitqueue_active(&h->wait)) {
+			spin_unlock(&rbio->bio_list_lock);
+			spin_unlock_irqrestore(&h->lock, flags);
+			wake_up(&h->wait);
+			goto done_nolock;
+		}
+	}
+done:
+	spin_unlock(&rbio->bio_list_lock);
+	spin_unlock_irqrestore(&h->lock, flags);
+
+done_nolock:
+	if (!keep_cache)
+		remove_rbio_from_cache(rbio);
+}
+
+static void __free_raid_bio(struct btrfs_raid_bio *rbio)
+{
+	int i;
+
+	WARN_ON(atomic_read(&rbio->refs) < 0);
+	if (!atomic_dec_and_test(&rbio->refs))
+		return;
+
+	WARN_ON(!list_empty(&rbio->stripe_cache));
+	WARN_ON(!list_empty(&rbio->hash_list));
+	WARN_ON(!bio_list_empty(&rbio->bio_list));
+
+	for (i = 0; i < rbio->nr_pages; i++) {
+		if (rbio->stripe_pages[i]) {
+			__free_page(rbio->stripe_pages[i]);
+			rbio->stripe_pages[i] = NULL;
+		}
+	}
+	kfree(rbio->raid_map);
+	kfree(rbio->bbio);
+	kfree(rbio);
+}
+
+static void free_raid_bio(struct btrfs_raid_bio *rbio)
+{
+	unlock_stripe(rbio);
+	__free_raid_bio(rbio);
+}
+
+/*
+ * this frees the rbio and runs through all the bios in the
+ * bio_list and calls end_io on them
+ */
+static void rbio_orig_end_io(struct btrfs_raid_bio *rbio, int err, int uptodate)
+{
+	struct bio *cur = bio_list_get(&rbio->bio_list);
+	struct bio *next;
+	free_raid_bio(rbio);
+
+	while (cur) {
+		next = cur->bi_next;
+		cur->bi_next = NULL;
+		if (uptodate)
+			set_bit(BIO_UPTODATE, &cur->bi_flags);
+		bio_endio(cur, err);
+		cur = next;
+	}
+}
+
+/*
+ * end io function used by finish_rmw.  When we finally
+ * get here, we've written a full stripe
+ */
+static void raid_write_end_io(struct bio *bio, int err)
+{
+	struct btrfs_raid_bio *rbio = bio->bi_private;
+
+	if (err)
+		fail_bio_stripe(rbio, bio);
+
+	bio_put(bio);
+
+	if (!atomic_dec_and_test(&rbio->bbio->stripes_pending))
+		return;
+
+	err = 0;
+
+	/* OK, we have read all the stripes we need to. */
+	if (atomic_read(&rbio->bbio->error) > rbio->bbio->max_errors)
+		err = -EIO;
+
+	rbio_orig_end_io(rbio, err, 0);
+	return;
+}
+
+/*
+ * the read/modify/write code wants to use the original bio for
+ * any pages it included, and then use the rbio for everything
+ * else.  This function decides if a given index (stripe number)
+ * and page number in that stripe fall inside the original bio
+ * or the rbio.
+ *
+ * if you set bio_list_only, you'll get a NULL back for any ranges
+ * that are outside the bio_list
+ *
+ * This doesn't take any refs on anything, you get a bare page pointer
+ * and the caller must bump refs as required.
+ *
+ * You must call index_rbio_pages once before you can trust
+ * the answers from this function.
+ */
+static struct page *page_in_rbio(struct btrfs_raid_bio *rbio,
+				 int index, int pagenr, int bio_list_only)
+{
+	int chunk_page;
+	struct page *p = NULL;
+
+	chunk_page = index * (rbio->stripe_len >> PAGE_SHIFT) + pagenr;
+
+	spin_lock_irq(&rbio->bio_list_lock);
+	p = rbio->bio_pages[chunk_page];
+	spin_unlock_irq(&rbio->bio_list_lock);
+
+	if (p || bio_list_only)
+		return p;
+
+	return rbio->stripe_pages[chunk_page];
+}
+
+/*
+ * number of pages we need for the entire stripe across all the
+ * drives
+ */
+static unsigned long rbio_nr_pages(unsigned long stripe_len, int nr_stripes)
+{
+	unsigned long nr = stripe_len * nr_stripes;
+	return (nr + PAGE_CACHE_SIZE - 1) >> PAGE_CACHE_SHIFT;
+}
+
+/*
+ * allocation and initial setup for the btrfs_raid_bio.  Not
+ * this does not allocate any pages for rbio->pages.
+ */
+static struct btrfs_raid_bio *alloc_rbio(struct btrfs_root *root,
+			  struct btrfs_bio *bbio, u64 *raid_map,
+			  u64 stripe_len)
+{
+	struct btrfs_raid_bio *rbio;
+	int nr_data = 0;
+	int num_pages = rbio_nr_pages(stripe_len, bbio->num_stripes);
+	void *p;
+
+	rbio = kzalloc(sizeof(*rbio) + num_pages * sizeof(struct page *) * 2,
+			GFP_NOFS);
+	if (!rbio) {
+		kfree(raid_map);
+		kfree(bbio);
+		return ERR_PTR(-ENOMEM);
+	}
+
+	bio_list_init(&rbio->bio_list);
+	INIT_LIST_HEAD(&rbio->plug_list);
+	spin_lock_init(&rbio->bio_list_lock);
+	INIT_LIST_HEAD(&rbio->stripe_cache);
+	INIT_LIST_HEAD(&rbio->hash_list);
+	rbio->bbio = bbio;
+	rbio->raid_map = raid_map;
+	rbio->fs_info = root->fs_info;
+	rbio->stripe_len = stripe_len;
+	rbio->nr_pages = num_pages;
+	rbio->faila = -1;
+	rbio->failb = -1;
+	atomic_set(&rbio->refs, 1);
+
+	/*
+	 * the stripe_pages and bio_pages array point to the extra
+	 * memory we allocated past the end of the rbio
+	 */
+	p = rbio + 1;
+	rbio->stripe_pages = p;
+	rbio->bio_pages = p + sizeof(struct page *) * num_pages;
+
+	if (raid_map[bbio->num_stripes - 1] == RAID6_Q_STRIPE)
+		nr_data = bbio->num_stripes - 2;
+	else
+		nr_data = bbio->num_stripes - 1;
+
+	rbio->nr_data = nr_data;
+	return rbio;
+}
+
+/* allocate pages for all the stripes in the bio, including parity */
+static int alloc_rbio_pages(struct btrfs_raid_bio *rbio)
+{
+	int i;
+	struct page *page;
+
+	for (i = 0; i < rbio->nr_pages; i++) {
+		if (rbio->stripe_pages[i])
+			continue;
+		page = alloc_page(GFP_NOFS | __GFP_HIGHMEM);
+		if (!page)
+			return -ENOMEM;
+		rbio->stripe_pages[i] = page;
+		ClearPageUptodate(page);
+	}
+	return 0;
+}
+
+/* allocate pages for just the p/q stripes */
+static int alloc_rbio_parity_pages(struct btrfs_raid_bio *rbio)
+{
+	int i;
+	struct page *page;
+
+	i = (rbio->nr_data * rbio->stripe_len) >> PAGE_CACHE_SHIFT;
+
+	for (; i < rbio->nr_pages; i++) {
+		if (rbio->stripe_pages[i])
+			continue;
+		page = alloc_page(GFP_NOFS | __GFP_HIGHMEM);
+		if (!page)
+			return -ENOMEM;
+		rbio->stripe_pages[i] = page;
+	}
+	return 0;
+}
+
+/*
+ * add a single page from a specific stripe into our list of bios for IO
+ * this will try to merge into existing bios if possible, and returns
+ * zero if all went well.
+ */
+int rbio_add_io_page(struct btrfs_raid_bio *rbio,
+		     struct bio_list *bio_list,
+		     struct page *page,
+		     int stripe_nr,
+		     unsigned long page_index,
+		     unsigned long bio_max_len)
+{
+	struct bio *last = bio_list->tail;
+	u64 last_end = 0;
+	int ret;
+	struct bio *bio;
+	struct btrfs_bio_stripe *stripe;
+	u64 disk_start;
+
+	stripe = &rbio->bbio->stripes[stripe_nr];
+	disk_start = stripe->physical + (page_index << PAGE_CACHE_SHIFT);
+
+	/* if the device is missing, just fail this stripe */
+	if (!stripe->dev->bdev)
+		return fail_rbio_index(rbio, stripe_nr);
+
+	/* see if we can add this page onto our existing bio */
+	if (last) {
+		last_end = (u64)last->bi_sector << 9;
+		last_end += last->bi_size;
+
+		/*
+		 * we can't merge these if they are from different
+		 * devices or if they are not contiguous
+		 */
+		if (last_end == disk_start && stripe->dev->bdev &&
+		    test_bit(BIO_UPTODATE, &last->bi_flags) &&
+		    last->bi_bdev == stripe->dev->bdev) {
+			ret = bio_add_page(last, page, PAGE_CACHE_SIZE, 0);
+			if (ret == PAGE_CACHE_SIZE)
+				return 0;
+		}
+	}
+
+	/* put a new bio on the list */
+	bio = bio_alloc(GFP_NOFS, bio_max_len >> PAGE_SHIFT?:1);
+	if (!bio)
+		return -ENOMEM;
+
+	bio->bi_size = 0;
+	bio->bi_bdev = stripe->dev->bdev;
+	bio->bi_sector = disk_start >> 9;
+	set_bit(BIO_UPTODATE, &bio->bi_flags);
+
+	bio_add_page(bio, page, PAGE_CACHE_SIZE, 0);
+	bio_list_add(bio_list, bio);
+	return 0;
+}
+
+/*
+ * while we're doing the read/modify/write cycle, we could
+ * have errors in reading pages off the disk.  This checks
+ * for errors and if we're not able to read the page it'll
+ * trigger parity reconstruction.  The rmw will be finished
+ * after we've reconstructed the failed stripes
+ */
+static void validate_rbio_for_rmw(struct btrfs_raid_bio *rbio)
+{
+	if (rbio->faila >= 0 || rbio->failb >= 0) {
+		BUG_ON(rbio->faila == rbio->bbio->num_stripes - 1);
+		__raid56_parity_recover(rbio);
+	} else {
+		finish_rmw(rbio);
+	}
+}
+
+/*
+ * these are just the pages from the rbio array, not from anything
+ * the FS sent down to us
+ */
+static struct page *rbio_stripe_page(struct btrfs_raid_bio *rbio, int stripe, int page)
+{
+	int index;
+	index = stripe * (rbio->stripe_len >> PAGE_CACHE_SHIFT);
+	index += page;
+	return rbio->stripe_pages[index];
+}
+
+/*
+ * helper function to walk our bio list and populate the bio_pages array with
+ * the result.  This seems expensive, but it is faster than constantly
+ * searching through the bio list as we setup the IO in finish_rmw or stripe
+ * reconstruction.
+ *
+ * This must be called before you trust the answers from page_in_rbio
+ */
+static void index_rbio_pages(struct btrfs_raid_bio *rbio)
+{
+	struct bio *bio;
+	u64 start;
+	unsigned long stripe_offset;
+	unsigned long page_index;
+	struct page *p;
+	int i;
+
+	spin_lock_irq(&rbio->bio_list_lock);
+	bio_list_for_each(bio, &rbio->bio_list) {
+		start = (u64)bio->bi_sector << 9;
+		stripe_offset = start - rbio->raid_map[0];
+		page_index = stripe_offset >> PAGE_CACHE_SHIFT;
+
+		for (i = 0; i < bio->bi_vcnt; i++) {
+			p = bio->bi_io_vec[i].bv_page;
+			rbio->bio_pages[page_index + i] = p;
+		}
+	}
+	spin_unlock_irq(&rbio->bio_list_lock);
+}
+
+/*
+ * this is called from one of two situations.  We either
+ * have a full stripe from the higher layers, or we've read all
+ * the missing bits off disk.
+ *
+ * This will calculate the parity and then send down any
+ * changed blocks.
+ */
+static noinline void finish_rmw(struct btrfs_raid_bio *rbio)
+{
+	struct btrfs_bio *bbio = rbio->bbio;
+	void *pointers[bbio->num_stripes];
+	int stripe_len = rbio->stripe_len;
+	int nr_data = rbio->nr_data;
+	int stripe;
+	int pagenr;
+	int p_stripe = -1;
+	int q_stripe = -1;
+	struct bio_list bio_list;
+	struct bio *bio;
+	int pages_per_stripe = stripe_len >> PAGE_CACHE_SHIFT;
+	int ret;
+
+	bio_list_init(&bio_list);
+
+	if (bbio->num_stripes - rbio->nr_data == 1) {
+		p_stripe = bbio->num_stripes - 1;
+	} else if (bbio->num_stripes - rbio->nr_data == 2) {
+		p_stripe = bbio->num_stripes - 2;
+		q_stripe = bbio->num_stripes - 1;
+	} else {
+		BUG();
+	}
+
+	/* at this point we either have a full stripe,
+	 * or we've read the full stripe from the drive.
+	 * recalculate the parity and write the new results.
+	 *
+	 * We're not allowed to add any new bios to the
+	 * bio list here, anyone else that wants to
+	 * change this stripe needs to do their own rmw.
+	 */
+	spin_lock_irq(&rbio->bio_list_lock);
+	set_bit(RBIO_RMW_LOCKED_BIT, &rbio->flags);
+	spin_unlock_irq(&rbio->bio_list_lock);
+
+	atomic_set(&rbio->bbio->error, 0);
+
+	/*
+	 * now that we've set rmw_locked, run through the
+	 * bio list one last time and map the page pointers
+	 *
+	 * We don't cache full rbios because we're assuming
+	 * the higher layers are unlikely to use this area of
+	 * the disk again soon.  If they do use it again,
+	 * hopefully they will send another full bio.
+	 */
+	index_rbio_pages(rbio);
+	if (!rbio_is_full(rbio))
+		cache_rbio_pages(rbio);
+	else
+		clear_bit(RBIO_CACHE_READY_BIT, &rbio->flags);
+
+	for (pagenr = 0; pagenr < pages_per_stripe; pagenr++) {
+		struct page *p;
+		/* first collect one page from each data stripe */
+		for (stripe = 0; stripe < nr_data; stripe++) {
+			p = page_in_rbio(rbio, stripe, pagenr, 0);
+			pointers[stripe] = kmap(p);
+		}
+
+		/* then add the parity stripe */
+		p = rbio_pstripe_page(rbio, pagenr);
+		SetPageUptodate(p);
+		pointers[stripe++] = kmap(p);
+
+		if (q_stripe != -1) {
+
+			/*
+			 * raid6, add the qstripe and call the
+			 * library function to fill in our p/q
+			 */
+			p = rbio_qstripe_page(rbio, pagenr);
+			SetPageUptodate(p);
+			pointers[stripe++] = kmap(p);
+
+			raid6_call.gen_syndrome(bbio->num_stripes, PAGE_SIZE,
+						pointers);
+		} else {
+			/* raid5 */
+			memcpy(pointers[nr_data], pointers[0], PAGE_SIZE);
+			run_xor(pointers + 1, nr_data - 1, PAGE_CACHE_SIZE);
+		}
+
+
+		for (stripe = 0; stripe < bbio->num_stripes; stripe++)
+			kunmap(page_in_rbio(rbio, stripe, pagenr, 0));
+	}
+
+	/*
+	 * time to start writing.  Make bios for everything from the
+	 * higher layers (the bio_list in our rbio) and our p/q.  Ignore
+	 * everything else.
+	 */
+	for (stripe = 0; stripe < bbio->num_stripes; stripe++) {
+		for (pagenr = 0; pagenr < pages_per_stripe; pagenr++) {
+			struct page *page;
+			if (stripe < rbio->nr_data) {
+				page = page_in_rbio(rbio, stripe, pagenr, 1);
+				if (!page)
+					continue;
+			} else {
+			       page = rbio_stripe_page(rbio, stripe, pagenr);
+			}
+
+			ret = rbio_add_io_page(rbio, &bio_list,
+				       page, stripe, pagenr, rbio->stripe_len);
+			if (ret)
+				goto cleanup;
+		}
+	}
+
+	atomic_set(&bbio->stripes_pending, bio_list_size(&bio_list));
+	BUG_ON(atomic_read(&bbio->stripes_pending) == 0);
+
+	while (1) {
+		bio = bio_list_pop(&bio_list);
+		if (!bio)
+			break;
+
+		bio->bi_private = rbio;
+		bio->bi_end_io = raid_write_end_io;
+		BUG_ON(!test_bit(BIO_UPTODATE, &bio->bi_flags));
+		submit_bio(WRITE, bio);
+	}
+	return;
+
+cleanup:
+	rbio_orig_end_io(rbio, -EIO, 0);
+}
+
+/*
+ * helper to find the stripe number for a given bio.  Used to figure out which
+ * stripe has failed.  This expects the bio to correspond to a physical disk,
+ * so it looks up based on physical sector numbers.
+ */
+static int find_bio_stripe(struct btrfs_raid_bio *rbio,
+			   struct bio *bio)
+{
+	u64 physical = bio->bi_sector;
+	u64 stripe_start;
+	int i;
+	struct btrfs_bio_stripe *stripe;
+
+	physical <<= 9;
+
+	for (i = 0; i < rbio->bbio->num_stripes; i++) {
+		stripe = &rbio->bbio->stripes[i];
+		stripe_start = stripe->physical;
+		if (physical >= stripe_start &&
+		    physical < stripe_start + rbio->stripe_len) {
+			return i;
+		}
+	}
+	return -1;
+}
+
+/*
+ * helper to find the stripe number for a given
+ * bio (before mapping).  Used to figure out which stripe has
+ * failed.  This looks up based on logical block numbers.
+ */
+static int find_logical_bio_stripe(struct btrfs_raid_bio *rbio,
+				   struct bio *bio)
+{
+	u64 logical = bio->bi_sector;
+	u64 stripe_start;
+	int i;
+
+	logical <<= 9;
+
+	for (i = 0; i < rbio->nr_data; i++) {
+		stripe_start = rbio->raid_map[i];
+		if (logical >= stripe_start &&
+		    logical < stripe_start + rbio->stripe_len) {
+			return i;
+		}
+	}
+	return -1;
+}
+
+/*
+ * returns -EIO if we had too many failures
+ */
+static int fail_rbio_index(struct btrfs_raid_bio *rbio, int failed)
+{
+	unsigned long flags;
+	int ret = 0;
+
+	spin_lock_irqsave(&rbio->bio_list_lock, flags);
+
+	/* we already know this stripe is bad, move on */
+	if (rbio->faila == failed || rbio->failb == failed)
+		goto out;
+
+	if (rbio->faila == -1) {
+		/* first failure on this rbio */
+		rbio->faila = failed;
+		atomic_inc(&rbio->bbio->error);
+	} else if (rbio->failb == -1) {
+		/* second failure on this rbio */
+		rbio->failb = failed;
+		atomic_inc(&rbio->bbio->error);
+	} else {
+		ret = -EIO;
+	}
+out:
+	spin_unlock_irqrestore(&rbio->bio_list_lock, flags);
+
+	return ret;
+}
+
+/*
+ * helper to fail a stripe based on a physical disk
+ * bio.
+ */
+static int fail_bio_stripe(struct btrfs_raid_bio *rbio,
+			   struct bio *bio)
+{
+	int failed = find_bio_stripe(rbio, bio);
+
+	if (failed < 0)
+		return -EIO;
+
+	return fail_rbio_index(rbio, failed);
+}
+
+/*
+ * this sets each page in the bio uptodate.  It should only be used on private
+ * rbio pages, nothing that comes in from the higher layers
+ */
+static void set_bio_pages_uptodate(struct bio *bio)
+{
+	int i;
+	struct page *p;
+
+	for (i = 0; i < bio->bi_vcnt; i++) {
+		p = bio->bi_io_vec[i].bv_page;
+		SetPageUptodate(p);
+	}
+}
+
+/*
+ * end io for the read phase of the rmw cycle.  All the bios here are physical
+ * stripe bios we've read from the disk so we can recalculate the parity of the
+ * stripe.
+ *
+ * This will usually kick off finish_rmw once all the bios are read in, but it
+ * may trigger parity reconstruction if we had any errors along the way
+ */
+static void raid_rmw_end_io(struct bio *bio, int err)
+{
+	struct btrfs_raid_bio *rbio = bio->bi_private;
+
+	if (err)
+		fail_bio_stripe(rbio, bio);
+	else
+		set_bio_pages_uptodate(bio);
+
+	bio_put(bio);
+
+	if (!atomic_dec_and_test(&rbio->bbio->stripes_pending))
+		return;
+
+	err = 0;
+	if (atomic_read(&rbio->bbio->error) > rbio->bbio->max_errors)
+		goto cleanup;
+
+	/*
+	 * this will normally call finish_rmw to start our write
+	 * but if there are any failed stripes we'll reconstruct
+	 * from parity first
+	 */
+	validate_rbio_for_rmw(rbio);
+	return;
+
+cleanup:
+
+	rbio_orig_end_io(rbio, -EIO, 0);
+}
+
+static void async_rmw_stripe(struct btrfs_raid_bio *rbio)
+{
+	rbio->work.flags = 0;
+	rbio->work.func = rmw_work;
+
+	btrfs_queue_worker(&rbio->fs_info->rmw_workers,
+			   &rbio->work);
+}
+
+static void async_read_rebuild(struct btrfs_raid_bio *rbio)
+{
+	rbio->work.flags = 0;
+	rbio->work.func = read_rebuild_work;
+
+	btrfs_queue_worker(&rbio->fs_info->rmw_workers,
+			   &rbio->work);
+}
+
+/*
+ * the stripe must be locked by the caller.  It will
+ * unlock after all the writes are done
+ */
+static int raid56_rmw_stripe(struct btrfs_raid_bio *rbio)
+{
+	int bios_to_read = 0;
+	struct btrfs_bio *bbio = rbio->bbio;
+	struct bio_list bio_list;
+	int ret;
+	int nr_pages = (rbio->stripe_len + PAGE_CACHE_SIZE - 1) >> PAGE_CACHE_SHIFT;
+	int pagenr;
+	int stripe;
+	struct bio *bio;
+
+	bio_list_init(&bio_list);
+
+	ret = alloc_rbio_pages(rbio);
+	if (ret)
+		goto cleanup;
+
+	index_rbio_pages(rbio);
+
+	atomic_set(&rbio->bbio->error, 0);
+	/*
+	 * build a list of bios to read all the missing parts of this
+	 * stripe
+	 */
+	for (stripe = 0; stripe < rbio->nr_data; stripe++) {
+		for (pagenr = 0; pagenr < nr_pages; pagenr++) {
+			struct page *page;
+			/*
+			 * we want to find all the pages missing from
+			 * the rbio and read them from the disk.  If
+			 * page_in_rbio finds a page in the bio list
+			 * we don't need to read it off the stripe.
+			 */
+			page = page_in_rbio(rbio, stripe, pagenr, 1);
+			if (page)
+				continue;
+
+			page = rbio_stripe_page(rbio, stripe, pagenr);
+			/*
+			 * the bio cache may have handed us an uptodate
+			 * page.  If so, be happy and use it
+			 */
+			if (PageUptodate(page))
+				continue;
+
+			ret = rbio_add_io_page(rbio, &bio_list, page,
+				       stripe, pagenr, rbio->stripe_len);
+			if (ret)
+				goto cleanup;
+		}
+	}
+
+	bios_to_read = bio_list_size(&bio_list);
+	if (!bios_to_read) {
+		/*
+		 * this can happen if others have merged with
+		 * us, it means there is nothing left to read.
+		 * But if there are missing devices it may not be
+		 * safe to do the full stripe write yet.
+		 */
+		goto finish;
+	}
+
+	/*
+	 * the bbio may be freed once we submit the last bio.  Make sure
+	 * not to touch it after that
+	 */
+	atomic_set(&bbio->stripes_pending, bios_to_read);
+	while (1) {
+		bio = bio_list_pop(&bio_list);
+		if (!bio)
+			break;
+
+		bio->bi_private = rbio;
+		bio->bi_end_io = raid_rmw_end_io;
+
+		btrfs_bio_wq_end_io(rbio->fs_info, bio,
+				    BTRFS_WQ_ENDIO_RAID56);
+
+		BUG_ON(!test_bit(BIO_UPTODATE, &bio->bi_flags));
+		submit_bio(READ, bio);
+	}
+	/* the actual write will happen once the reads are done */
+	return 0;
+
+cleanup:
+	rbio_orig_end_io(rbio, -EIO, 0);
+	return -EIO;
+
+finish:
+	validate_rbio_for_rmw(rbio);
+	return 0;
+}
+
+/*
+ * if the upper layers pass in a full stripe, we thank them by only allocating
+ * enough pages to hold the parity, and sending it all down quickly.
+ */
+static int full_stripe_write(struct btrfs_raid_bio *rbio)
+{
+	int ret;
+
+	ret = alloc_rbio_parity_pages(rbio);
+	if (ret)
+		return ret;
+
+	ret = lock_stripe_add(rbio);
+	if (ret == 0)
+		finish_rmw(rbio);
+	return 0;
+}
+
+/*
+ * partial stripe writes get handed over to async helpers.
+ * We're really hoping to merge a few more writes into this
+ * rbio before calculating new parity
+ */
+static int partial_stripe_write(struct btrfs_raid_bio *rbio)
+{
+	int ret;
+
+	ret = lock_stripe_add(rbio);
+	if (ret == 0)
+		async_rmw_stripe(rbio);
+	return 0;
+}
+
+/*
+ * sometimes while we were reading from the drive to
+ * recalculate parity, enough new bios come into create
+ * a full stripe.  So we do a check here to see if we can
+ * go directly to finish_rmw
+ */
+static int __raid56_parity_write(struct btrfs_raid_bio *rbio)
+{
+	/* head off into rmw land if we don't have a full stripe */
+	if (!rbio_is_full(rbio))
+		return partial_stripe_write(rbio);
+	return full_stripe_write(rbio);
+}
+
+/*
+ * We use plugging call backs to collect full stripes.
+ * Any time we get a partial stripe write while plugged
+ * we collect it into a list.  When the unplug comes down,
+ * we sort the list by logical block number and merge
+ * everything we can into the same rbios
+ */
+struct btrfs_plug_cb {
+	struct blk_plug_cb cb;
+	struct btrfs_fs_info *info;
+	struct list_head rbio_list;
+	struct btrfs_work work;
+};
+
+/*
+ * rbios on the plug list are sorted for easier merging.
+ */
+static int plug_cmp(void *priv, struct list_head *a, struct list_head *b)
+{
+	struct btrfs_raid_bio *ra = container_of(a, struct btrfs_raid_bio,
+						 plug_list);
+	struct btrfs_raid_bio *rb = container_of(b, struct btrfs_raid_bio,
+						 plug_list);
+	u64 a_sector = ra->bio_list.head->bi_sector;
+	u64 b_sector = rb->bio_list.head->bi_sector;
+
+	if (a_sector < b_sector)
+		return -1;
+	if (a_sector > b_sector)
+		return 1;
+	return 0;
+}
+
+static void run_plug(struct btrfs_plug_cb *plug)
+{
+	struct btrfs_raid_bio *cur;
+	struct btrfs_raid_bio *last = NULL;
+
+	/*
+	 * sort our plug list then try to merge
+	 * everything we can in hopes of creating full
+	 * stripes.
+	 */
+	list_sort(NULL, &plug->rbio_list, plug_cmp);
+	while (!list_empty(&plug->rbio_list)) {
+		cur = list_entry(plug->rbio_list.next,
+				 struct btrfs_raid_bio, plug_list);
+		list_del_init(&cur->plug_list);
+
+		if (rbio_is_full(cur)) {
+			/* we have a full stripe, send it down */
+			full_stripe_write(cur);
+			continue;
+		}
+		if (last) {
+			if (rbio_can_merge(last, cur)) {
+				merge_rbio(last, cur);
+				__free_raid_bio(cur);
+				continue;
+
+			}
+			__raid56_parity_write(last);
+		}
+		last = cur;
+	}
+	if (last) {
+		__raid56_parity_write(last);
+	}
+	kfree(plug);
+}
+
+/*
+ * if the unplug comes from schedule, we have to push the
+ * work off to a helper thread
+ */
+static void unplug_work(struct btrfs_work *work)
+{
+	struct btrfs_plug_cb *plug;
+	plug = container_of(work, struct btrfs_plug_cb, work);
+	run_plug(plug);
+}
+
+static void btrfs_raid_unplug(struct blk_plug_cb *cb, bool from_schedule)
+{
+	struct btrfs_plug_cb *plug;
+	plug = container_of(cb, struct btrfs_plug_cb, cb);
+
+	if (from_schedule) {
+		plug->work.flags = 0;
+		plug->work.func = unplug_work;
+		btrfs_queue_worker(&plug->info->rmw_workers,
+				   &plug->work);
+		return;
+	}
+	run_plug(plug);
+}
+
+/*
+ * our main entry point for writes from the rest of the FS.
+ */
+int raid56_parity_write(struct btrfs_root *root, struct bio *bio,
+			struct btrfs_bio *bbio, u64 *raid_map,
+			u64 stripe_len)
+{
+	struct btrfs_raid_bio *rbio;
+	struct btrfs_plug_cb *plug = NULL;
+	struct blk_plug_cb *cb;
+
+	rbio = alloc_rbio(root, bbio, raid_map, stripe_len);
+	if (IS_ERR(rbio)) {
+		kfree(raid_map);
+		kfree(bbio);
+		return PTR_ERR(rbio);
+	}
+	bio_list_add(&rbio->bio_list, bio);
+	rbio->bio_list_bytes = bio->bi_size;
+
+	/*
+	 * don't plug on full rbios, just get them out the door
+	 * as quickly as we can
+	 */
+	if (rbio_is_full(rbio))
+		return full_stripe_write(rbio);
+
+	cb = blk_check_plugged(btrfs_raid_unplug, root->fs_info,
+			       sizeof(*plug));
+	if (cb) {
+		plug = container_of(cb, struct btrfs_plug_cb, cb);
+		if (!plug->info) {
+			plug->info = root->fs_info;
+			INIT_LIST_HEAD(&plug->rbio_list);
+		}
+		list_add_tail(&rbio->plug_list, &plug->rbio_list);
+	} else {
+		return __raid56_parity_write(rbio);
+	}
+	return 0;
+}
+
+/*
+ * all parity reconstruction happens here.  We've read in everything
+ * we can find from the drives and this does the heavy lifting of
+ * sorting the good from the bad.
+ */
+static void __raid_recover_end_io(struct btrfs_raid_bio *rbio)
+{
+	int pagenr, stripe;
+	void **pointers;
+	int faila = -1, failb = -1;
+	int nr_pages = (rbio->stripe_len + PAGE_CACHE_SIZE - 1) >> PAGE_CACHE_SHIFT;
+	struct page *page;
+	int err;
+	int i;
+
+	pointers = kzalloc(rbio->bbio->num_stripes * sizeof(void *),
+			   GFP_NOFS);
+	if (!pointers) {
+		err = -ENOMEM;
+		goto cleanup_io;
+	}
+
+	faila = rbio->faila;
+	failb = rbio->failb;
+
+	if (rbio->read_rebuild) {
+		spin_lock_irq(&rbio->bio_list_lock);
+		set_bit(RBIO_RMW_LOCKED_BIT, &rbio->flags);
+		spin_unlock_irq(&rbio->bio_list_lock);
+	}
+
+	index_rbio_pages(rbio);
+
+	for (pagenr = 0; pagenr < nr_pages; pagenr++) {
+		/* setup our array of pointers with pages
+		 * from each stripe
+		 */
+		for (stripe = 0; stripe < rbio->bbio->num_stripes; stripe++) {
+			/*
+			 * if we're rebuilding a read, we have to use
+			 * pages from the bio list
+			 */
+			if (rbio->read_rebuild &&
+			    (stripe == faila || stripe == failb)) {
+				page = page_in_rbio(rbio, stripe, pagenr, 0);
+			} else {
+				page = rbio_stripe_page(rbio, stripe, pagenr);
+			}
+			pointers[stripe] = kmap(page);
+		}
+
+		/* all raid6 handling here */
+		if (rbio->raid_map[rbio->bbio->num_stripes - 1] ==
+		    RAID6_Q_STRIPE) {
+
+			/*
+			 * single failure, rebuild from parity raid5
+			 * style
+			 */
+			if (failb < 0) {
+				if (faila == rbio->nr_data) {
+					/*
+					 * Just the P stripe has failed, without
+					 * a bad data or Q stripe.
+					 * TODO, we should redo the xor here.
+					 */
+					err = -EIO;
+					goto cleanup;
+				}
+				/*
+				 * a single failure in raid6 is rebuilt
+				 * in the pstripe code below
+				 */
+				goto pstripe;
+			}
+
+			/* make sure our ps and qs are in order */
+			if (faila > failb) {
+				int tmp = failb;
+				failb = faila;
+				faila = tmp;
+			}
+
+			/* if the q stripe is failed, do a pstripe reconstruction
+			 * from the xors.
+			 * If both the q stripe and the P stripe are failed, we're
+			 * here due to a crc mismatch and we can't give them the
+			 * data they want
+			 */
+			if (rbio->raid_map[failb] == RAID6_Q_STRIPE) {
+				if (rbio->raid_map[faila] == RAID5_P_STRIPE) {
+					err = -EIO;
+					goto cleanup;
+				}
+				/*
+				 * otherwise we have one bad data stripe and
+				 * a good P stripe.  raid5!
+				 */
+				goto pstripe;
+			}
+
+			if (rbio->raid_map[failb] == RAID5_P_STRIPE) {
+				raid6_datap_recov(rbio->bbio->num_stripes,
+						  PAGE_SIZE, faila, pointers);
+			} else {
+				raid6_2data_recov(rbio->bbio->num_stripes,
+						  PAGE_SIZE, faila, failb,
+						  pointers);
+			}
+		} else {
+			void *p;
+
+			/* rebuild from P stripe here (raid5 or raid6) */
+			BUG_ON(failb != -1);
+pstripe:
+			/* Copy parity block into failed block to start with */
+			memcpy(pointers[faila],
+			       pointers[rbio->nr_data],
+			       PAGE_CACHE_SIZE);
+
+			/* rearrange the pointer array */
+			p = pointers[faila];
+			for (stripe = faila; stripe < rbio->nr_data - 1; stripe++)
+				pointers[stripe] = pointers[stripe + 1];
+			pointers[rbio->nr_data - 1] = p;
+
+			/* xor in the rest */
+			run_xor(pointers, rbio->nr_data - 1, PAGE_CACHE_SIZE);
+		}
+		/* if we're doing this rebuild as part of an rmw, go through
+		 * and set all of our private rbio pages in the
+		 * failed stripes as uptodate.  This way finish_rmw will
+		 * know they can be trusted.  If this was a read reconstruction,
+		 * other endio functions will fiddle the uptodate bits
+		 */
+		if (!rbio->read_rebuild) {
+			for (i = 0;  i < nr_pages; i++) {
+				if (faila != -1) {
+					page = rbio_stripe_page(rbio, faila, i);
+					SetPageUptodate(page);
+				}
+				if (failb != -1) {
+					page = rbio_stripe_page(rbio, failb, i);
+					SetPageUptodate(page);
+				}
+			}
+		}
+		for (stripe = 0; stripe < rbio->bbio->num_stripes; stripe++) {
+			/*
+			 * if we're rebuilding a read, we have to use
+			 * pages from the bio list
+			 */
+			if (rbio->read_rebuild &&
+			    (stripe == faila || stripe == failb)) {
+				page = page_in_rbio(rbio, stripe, pagenr, 0);
+			} else {
+				page = rbio_stripe_page(rbio, stripe, pagenr);
+			}
+			kunmap(page);
+		}
+	}
+
+	err = 0;
+cleanup:
+	kfree(pointers);
+
+cleanup_io:
+
+	if (rbio->read_rebuild) {
+		if (err == 0)
+			cache_rbio_pages(rbio);
+		else
+			clear_bit(RBIO_CACHE_READY_BIT, &rbio->flags);
+
+		rbio_orig_end_io(rbio, err, err == 0);
+	} else if (err == 0) {
+		rbio->faila = -1;
+		rbio->failb = -1;
+		finish_rmw(rbio);
+	} else {
+		rbio_orig_end_io(rbio, err, 0);
+	}
+}
+
+/*
+ * This is called only for stripes we've read from disk to
+ * reconstruct the parity.
+ */
+static void raid_recover_end_io(struct bio *bio, int err)
+{
+	struct btrfs_raid_bio *rbio = bio->bi_private;
+
+	/*
+	 * we only read stripe pages off the disk, set them
+	 * up to date if there were no errors
+	 */
+	if (err)
+		fail_bio_stripe(rbio, bio);
+	else
+		set_bio_pages_uptodate(bio);
+	bio_put(bio);
+
+	if (!atomic_dec_and_test(&rbio->bbio->stripes_pending))
+		return;
+
+	if (atomic_read(&rbio->bbio->error) > rbio->bbio->max_errors)
+		rbio_orig_end_io(rbio, -EIO, 0);
+	else
+		__raid_recover_end_io(rbio);
+}
+
+/*
+ * reads everything we need off the disk to reconstruct
+ * the parity. endio handlers trigger final reconstruction
+ * when the IO is done.
+ *
+ * This is used both for reads from the higher layers and for
+ * parity construction required to finish a rmw cycle.
+ */
+static int __raid56_parity_recover(struct btrfs_raid_bio *rbio)
+{
+	int bios_to_read = 0;
+	struct btrfs_bio *bbio = rbio->bbio;
+	struct bio_list bio_list;
+	int ret;
+	int nr_pages = (rbio->stripe_len + PAGE_CACHE_SIZE - 1) >> PAGE_CACHE_SHIFT;
+	int pagenr;
+	int stripe;
+	struct bio *bio;
+
+	bio_list_init(&bio_list);
+
+	ret = alloc_rbio_pages(rbio);
+	if (ret)
+		goto cleanup;
+
+	atomic_set(&rbio->bbio->error, 0);
+
+	/*
+	 * read everything that hasn't failed.  Thanks to the
+	 * stripe cache, it is possible that some or all of these
+	 * pages are going to be uptodate.
+	 */
+	for (stripe = 0; stripe < bbio->num_stripes; stripe++) {
+		if (rbio->faila == stripe ||
+		    rbio->failb == stripe)
+			continue;
+
+		for (pagenr = 0; pagenr < nr_pages; pagenr++) {
+			struct page *p;
+
+			/*
+			 * the rmw code may have already read this
+			 * page in
+			 */
+			p = rbio_stripe_page(rbio, stripe, pagenr);
+			if (PageUptodate(p))
+				continue;
+
+			ret = rbio_add_io_page(rbio, &bio_list,
+				       rbio_stripe_page(rbio, stripe, pagenr),
+				       stripe, pagenr, rbio->stripe_len);
+			if (ret < 0)
+				goto cleanup;
+		}
+	}
+
+	bios_to_read = bio_list_size(&bio_list);
+	if (!bios_to_read) {
+		/*
+		 * we might have no bios to read just because the pages
+		 * were up to date, or we might have no bios to read because
+		 * the devices were gone.
+		 */
+		if (atomic_read(&rbio->bbio->error) <= rbio->bbio->max_errors) {
+			__raid_recover_end_io(rbio);
+			goto out;
+		} else {
+			goto cleanup;
+		}
+	}
+
+	/*
+	 * the bbio may be freed once we submit the last bio.  Make sure
+	 * not to touch it after that
+	 */
+	atomic_set(&bbio->stripes_pending, bios_to_read);
+	while (1) {
+		bio = bio_list_pop(&bio_list);
+		if (!bio)
+			break;
+
+		bio->bi_private = rbio;
+		bio->bi_end_io = raid_recover_end_io;
+
+		btrfs_bio_wq_end_io(rbio->fs_info, bio,
+				    BTRFS_WQ_ENDIO_RAID56);
+
+		BUG_ON(!test_bit(BIO_UPTODATE, &bio->bi_flags));
+		submit_bio(READ, bio);
+	}
+out:
+	return 0;
+
+cleanup:
+	if (rbio->read_rebuild)
+		rbio_orig_end_io(rbio, -EIO, 0);
+	return -EIO;
+}
+
+/*
+ * the main entry point for reads from the higher layers.  This
+ * is really only called when the normal read path had a failure,
+ * so we assume the bio they send down corresponds to a failed part
+ * of the drive.
+ */
+int raid56_parity_recover(struct btrfs_root *root, struct bio *bio,
+			  struct btrfs_bio *bbio, u64 *raid_map,
+			  u64 stripe_len, int mirror_num)
+{
+	struct btrfs_raid_bio *rbio;
+	int ret;
+
+	rbio = alloc_rbio(root, bbio, raid_map, stripe_len);
+	if (IS_ERR(rbio)) {
+		return PTR_ERR(rbio);
+	}
+
+	rbio->read_rebuild = 1;
+	bio_list_add(&rbio->bio_list, bio);
+	rbio->bio_list_bytes = bio->bi_size;
+
+	rbio->faila = find_logical_bio_stripe(rbio, bio);
+	if (rbio->faila == -1) {
+		BUG();
+		kfree(rbio);
+		return -EIO;
+	}
+
+	/*
+	 * reconstruct from the q stripe if they are
+	 * asking for mirror 3
+	 */
+	if (mirror_num == 3)
+		rbio->failb = bbio->num_stripes - 2;
+
+	ret = lock_stripe_add(rbio);
+
+	/*
+	 * __raid56_parity_recover will end the bio with
+	 * any errors it hits.  We don't want to return
+	 * its error value up the stack because our caller
+	 * will end up calling bio_endio with any nonzero
+	 * return
+	 */
+	if (ret == 0)
+		__raid56_parity_recover(rbio);
+	/*
+	 * our rbio has been added to the list of
+	 * rbios that will be handled after the
+	 * currently lock owner is done
+	 */
+	return 0;
+
+}
+
+static void rmw_work(struct btrfs_work *work)
+{
+	struct btrfs_raid_bio *rbio;
+
+	rbio = container_of(work, struct btrfs_raid_bio, work);
+	raid56_rmw_stripe(rbio);
+}
+
+static void read_rebuild_work(struct btrfs_work *work)
+{
+	struct btrfs_raid_bio *rbio;
+
+	rbio = container_of(work, struct btrfs_raid_bio, work);
+	__raid56_parity_recover(rbio);
+}
diff --git a/fs/btrfs/raid56.h b/fs/btrfs/raid56.h
new file mode 100644
index 0000000..ea5d73b
--- /dev/null
+++ b/fs/btrfs/raid56.h
@@ -0,0 +1,51 @@
+/*
+ * Copyright (C) 2012 Fusion-io  All rights reserved.
+ * Copyright (C) 2012 Intel Corp. All rights reserved.
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public
+ * License v2 as published by the Free Software Foundation.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public
+ * License along with this program; if not, write to the
+ * Free Software Foundation, Inc., 59 Temple Place - Suite 330,
+ * Boston, MA 021110-1307, USA.
+ */
+
+#ifndef __BTRFS_RAID56__
+#define __BTRFS_RAID56__
+static inline int nr_parity_stripes(struct map_lookup *map)
+{
+	if (map->type & BTRFS_BLOCK_GROUP_RAID5)
+		return 1;
+	else if (map->type & BTRFS_BLOCK_GROUP_RAID6)
+		return 2;
+	else
+		return 0;
+}
+
+static inline int nr_data_stripes(struct map_lookup *map)
+{
+	return map->num_stripes - nr_parity_stripes(map);
+}
+#define RAID5_P_STRIPE ((u64)-2)
+#define RAID6_Q_STRIPE ((u64)-1)
+
+#define is_parity_stripe(x) (((x) == RAID5_P_STRIPE) ||		\
+			     ((x) == RAID6_Q_STRIPE))
+
+int raid56_parity_recover(struct btrfs_root *root, struct bio *bio,
+				 struct btrfs_bio *bbio, u64 *raid_map,
+				 u64 stripe_len, int mirror_num);
+int raid56_parity_write(struct btrfs_root *root, struct bio *bio,
+			       struct btrfs_bio *bbio, u64 *raid_map,
+			       u64 stripe_len);
+
+int btrfs_alloc_stripe_hash_table(struct btrfs_fs_info *info);
+void btrfs_free_stripe_hash_table(struct btrfs_fs_info *info);
+#endif
diff --git a/fs/btrfs/scrub.c b/fs/btrfs/scrub.c
index c78b2a3..53c3501 100644
--- a/fs/btrfs/scrub.c
+++ b/fs/btrfs/scrub.c
@@ -28,6 +28,7 @@
 #include "dev-replace.h"
 #include "check-integrity.h"
 #include "rcu-string.h"
+#include "raid56.h"
 
 /*
  * This is only the first step towards a full-features scrub. It reads all
@@ -2254,6 +2255,13 @@
 	struct btrfs_device *extent_dev;
 	int extent_mirror_num;
 
+	if (map->type & (BTRFS_BLOCK_GROUP_RAID5 |
+			 BTRFS_BLOCK_GROUP_RAID6)) {
+		if (num >= nr_data_stripes(map)) {
+			return 0;
+		}
+	}
+
 	nstripes = length;
 	offset = 0;
 	do_div(nstripes, map->stripe_len);
diff --git a/fs/btrfs/transaction.c b/fs/btrfs/transaction.c
index 955204c..a83d486 100644
--- a/fs/btrfs/transaction.c
+++ b/fs/btrfs/transaction.c
@@ -167,6 +167,9 @@
 
 	spin_lock_init(&cur_trans->commit_lock);
 	spin_lock_init(&cur_trans->delayed_refs.lock);
+	atomic_set(&cur_trans->delayed_refs.procs_running_refs, 0);
+	atomic_set(&cur_trans->delayed_refs.ref_seq, 0);
+	init_waitqueue_head(&cur_trans->delayed_refs.wait);
 
 	INIT_LIST_HEAD(&cur_trans->pending_snapshots);
 	INIT_LIST_HEAD(&cur_trans->ordered_operations);
@@ -637,7 +640,7 @@
 	if (!list_empty(&trans->new_bgs))
 		btrfs_create_pending_block_groups(trans, root);
 
-	while (count < 2) {
+	while (count < 1) {
 		unsigned long cur = trans->delayed_ref_updates;
 		trans->delayed_ref_updates = 0;
 		if (cur &&
@@ -649,6 +652,7 @@
 		}
 		count++;
 	}
+
 	btrfs_trans_release_metadata(trans, root);
 	trans->block_rsv = NULL;
 
@@ -744,7 +748,9 @@
 	struct extent_state *cached_state = NULL;
 	u64 start = 0;
 	u64 end;
+	struct blk_plug plug;
 
+	blk_start_plug(&plug);
 	while (!find_first_extent_bit(dirty_pages, start, &start, &end,
 				      mark, &cached_state)) {
 		convert_extent_bit(dirty_pages, start, end, EXTENT_NEED_WAIT,
@@ -758,6 +764,7 @@
 	}
 	if (err)
 		werr = err;
+	blk_finish_plug(&plug);
 	return werr;
 }
 
diff --git a/fs/btrfs/volumes.c b/fs/btrfs/volumes.c
index 72b1cf1..7992dc4 100644
--- a/fs/btrfs/volumes.c
+++ b/fs/btrfs/volumes.c
@@ -25,6 +25,8 @@
 #include <linux/capability.h>
 #include <linux/ratelimit.h>
 #include <linux/kthread.h>
+#include <linux/raid/pq.h>
+#include <asm/div64.h>
 #include "compat.h"
 #include "ctree.h"
 #include "extent_map.h"
@@ -32,6 +34,7 @@
 #include "transaction.h"
 #include "print-tree.h"
 #include "volumes.h"
+#include "raid56.h"
 #include "async-thread.h"
 #include "check-integrity.h"
 #include "rcu-string.h"
@@ -1465,6 +1468,21 @@
 		goto out;
 	}
 
+	if ((all_avail & BTRFS_BLOCK_GROUP_RAID5) &&
+	    root->fs_info->fs_devices->rw_devices <= 2) {
+		printk(KERN_ERR "btrfs: unable to go below two "
+		       "devices on raid5\n");
+		ret = -EINVAL;
+		goto out;
+	}
+	if ((all_avail & BTRFS_BLOCK_GROUP_RAID6) &&
+	    root->fs_info->fs_devices->rw_devices <= 3) {
+		printk(KERN_ERR "btrfs: unable to go below three "
+		       "devices on raid6\n");
+		ret = -EINVAL;
+		goto out;
+	}
+
 	if (strcmp(device_path, "missing") == 0) {
 		struct list_head *devices;
 		struct btrfs_device *tmp;
@@ -2726,11 +2744,15 @@
 		return 0;
 
 	if (btrfs_chunk_type(leaf, chunk) & (BTRFS_BLOCK_GROUP_DUP |
-	     BTRFS_BLOCK_GROUP_RAID1 | BTRFS_BLOCK_GROUP_RAID10))
-		factor = 2;
-	else
-		factor = 1;
-	factor = num_stripes / factor;
+	     BTRFS_BLOCK_GROUP_RAID1 | BTRFS_BLOCK_GROUP_RAID10)) {
+		factor = num_stripes / 2;
+	} else if (btrfs_chunk_type(leaf, chunk) & BTRFS_BLOCK_GROUP_RAID5) {
+		factor = num_stripes - 1;
+	} else if (btrfs_chunk_type(leaf, chunk) & BTRFS_BLOCK_GROUP_RAID6) {
+		factor = num_stripes - 2;
+	} else {
+		factor = num_stripes;
+	}
 
 	for (i = 0; i < num_stripes; i++) {
 		stripe = btrfs_stripe_nr(chunk, i);
@@ -3090,7 +3112,9 @@
 		allowed |= (BTRFS_BLOCK_GROUP_RAID0 | BTRFS_BLOCK_GROUP_RAID1);
 	else
 		allowed |= (BTRFS_BLOCK_GROUP_RAID0 | BTRFS_BLOCK_GROUP_RAID1 |
-				BTRFS_BLOCK_GROUP_RAID10);
+				BTRFS_BLOCK_GROUP_RAID10 |
+				BTRFS_BLOCK_GROUP_RAID5 |
+				BTRFS_BLOCK_GROUP_RAID6);
 
 	if ((bctl->data.flags & BTRFS_BALANCE_ARGS_CONVERT) &&
 	    (!alloc_profile_is_valid(bctl->data.target, 1) ||
@@ -3130,7 +3154,9 @@
 
 	/* allow to reduce meta or sys integrity only if force set */
 	allowed = BTRFS_BLOCK_GROUP_DUP | BTRFS_BLOCK_GROUP_RAID1 |
-			BTRFS_BLOCK_GROUP_RAID10;
+			BTRFS_BLOCK_GROUP_RAID10 |
+			BTRFS_BLOCK_GROUP_RAID5 |
+			BTRFS_BLOCK_GROUP_RAID6;
 	do {
 		seq = read_seqbegin(&fs_info->profiles_lock);
 
@@ -3204,11 +3230,6 @@
 		update_ioctl_balance_args(fs_info, 0, bargs);
 	}
 
-	if ((ret && ret != -ECANCELED && ret != -ENOSPC) ||
-	    balance_need_close(fs_info)) {
-		__cancel_balance(fs_info);
-	}
-
 	wake_up(&fs_info->balance_wait_q);
 
 	return ret;
@@ -3611,8 +3632,46 @@
 		.devs_increment	= 1,
 		.ncopies	= 1,
 	},
+	[BTRFS_RAID_RAID5] = {
+		.sub_stripes	= 1,
+		.dev_stripes	= 1,
+		.devs_max	= 0,
+		.devs_min	= 2,
+		.devs_increment	= 1,
+		.ncopies	= 2,
+	},
+	[BTRFS_RAID_RAID6] = {
+		.sub_stripes	= 1,
+		.dev_stripes	= 1,
+		.devs_max	= 0,
+		.devs_min	= 3,
+		.devs_increment	= 1,
+		.ncopies	= 3,
+	},
 };
- 
+
+static u32 find_raid56_stripe_len(u32 data_devices, u32 dev_stripe_target)
+{
+	/* TODO allow them to set a preferred stripe size */
+	return 64 * 1024;
+}
+
+static void check_raid56_incompat_flag(struct btrfs_fs_info *info, u64 type)
+{
+	u64 features;
+
+	if (!(type & (BTRFS_BLOCK_GROUP_RAID5 | BTRFS_BLOCK_GROUP_RAID6)))
+		return;
+
+	features = btrfs_super_incompat_flags(info->super_copy);
+	if (features & BTRFS_FEATURE_INCOMPAT_RAID56)
+		return;
+
+	features |= BTRFS_FEATURE_INCOMPAT_RAID56;
+	btrfs_set_super_incompat_flags(info->super_copy, features);
+	printk(KERN_INFO "btrfs: setting RAID5/6 feature flag\n");
+}
+
 static int __btrfs_alloc_chunk(struct btrfs_trans_handle *trans,
 			       struct btrfs_root *extent_root,
 			       struct map_lookup **map_ret,
@@ -3628,6 +3687,8 @@
 	struct btrfs_device_info *devices_info = NULL;
 	u64 total_avail;
 	int num_stripes;	/* total number of stripes to allocate */
+	int data_stripes;	/* number of stripes that count for
+				   block group size */
 	int sub_stripes;	/* sub_stripes info for map */
 	int dev_stripes;	/* stripes per dev */
 	int devs_max;		/* max devs to use */
@@ -3639,6 +3700,7 @@
 	u64 max_chunk_size;
 	u64 stripe_size;
 	u64 num_bytes;
+	u64 raid_stripe_len = BTRFS_STRIPE_LEN;
 	int ndevs;
 	int i;
 	int j;
@@ -3768,16 +3830,31 @@
 	stripe_size = devices_info[ndevs-1].max_avail;
 	num_stripes = ndevs * dev_stripes;
 
+	/*
+	 * this will have to be fixed for RAID1 and RAID10 over
+	 * more drives
+	 */
+	data_stripes = num_stripes / ncopies;
+
 	if (stripe_size * ndevs > max_chunk_size * ncopies) {
 		stripe_size = max_chunk_size * ncopies;
 		do_div(stripe_size, ndevs);
 	}
-
+	if (type & BTRFS_BLOCK_GROUP_RAID5) {
+		raid_stripe_len = find_raid56_stripe_len(ndevs - 1,
+				 btrfs_super_stripesize(info->super_copy));
+		data_stripes = num_stripes - 1;
+	}
+	if (type & BTRFS_BLOCK_GROUP_RAID6) {
+		raid_stripe_len = find_raid56_stripe_len(ndevs - 2,
+				 btrfs_super_stripesize(info->super_copy));
+		data_stripes = num_stripes - 2;
+	}
 	do_div(stripe_size, dev_stripes);
 
 	/* align to BTRFS_STRIPE_LEN */
-	do_div(stripe_size, BTRFS_STRIPE_LEN);
-	stripe_size *= BTRFS_STRIPE_LEN;
+	do_div(stripe_size, raid_stripe_len);
+	stripe_size *= raid_stripe_len;
 
 	map = kmalloc(map_lookup_size(num_stripes), GFP_NOFS);
 	if (!map) {
@@ -3795,14 +3872,14 @@
 		}
 	}
 	map->sector_size = extent_root->sectorsize;
-	map->stripe_len = BTRFS_STRIPE_LEN;
-	map->io_align = BTRFS_STRIPE_LEN;
-	map->io_width = BTRFS_STRIPE_LEN;
+	map->stripe_len = raid_stripe_len;
+	map->io_align = raid_stripe_len;
+	map->io_width = raid_stripe_len;
 	map->type = type;
 	map->sub_stripes = sub_stripes;
 
 	*map_ret = map;
-	num_bytes = stripe_size * (num_stripes / ncopies);
+	num_bytes = stripe_size * data_stripes;
 
 	*stripe_size_out = stripe_size;
 	*num_bytes_out = num_bytes;
@@ -3853,6 +3930,8 @@
 	}
 
 	free_extent_map(em);
+	check_raid56_incompat_flag(extent_root->fs_info, type);
+
 	kfree(devices_info);
 	return 0;
 
@@ -4136,6 +4215,10 @@
 		ret = map->num_stripes;
 	else if (map->type & BTRFS_BLOCK_GROUP_RAID10)
 		ret = map->sub_stripes;
+	else if (map->type & BTRFS_BLOCK_GROUP_RAID5)
+		ret = 2;
+	else if (map->type & BTRFS_BLOCK_GROUP_RAID6)
+		ret = 3;
 	else
 		ret = 1;
 	free_extent_map(em);
@@ -4148,6 +4231,52 @@
 	return ret;
 }
 
+unsigned long btrfs_full_stripe_len(struct btrfs_root *root,
+				    struct btrfs_mapping_tree *map_tree,
+				    u64 logical)
+{
+	struct extent_map *em;
+	struct map_lookup *map;
+	struct extent_map_tree *em_tree = &map_tree->map_tree;
+	unsigned long len = root->sectorsize;
+
+	read_lock(&em_tree->lock);
+	em = lookup_extent_mapping(em_tree, logical, len);
+	read_unlock(&em_tree->lock);
+	BUG_ON(!em);
+
+	BUG_ON(em->start > logical || em->start + em->len < logical);
+	map = (struct map_lookup *)em->bdev;
+	if (map->type & (BTRFS_BLOCK_GROUP_RAID5 |
+			 BTRFS_BLOCK_GROUP_RAID6)) {
+		len = map->stripe_len * nr_data_stripes(map);
+	}
+	free_extent_map(em);
+	return len;
+}
+
+int btrfs_is_parity_mirror(struct btrfs_mapping_tree *map_tree,
+			   u64 logical, u64 len, int mirror_num)
+{
+	struct extent_map *em;
+	struct map_lookup *map;
+	struct extent_map_tree *em_tree = &map_tree->map_tree;
+	int ret = 0;
+
+	read_lock(&em_tree->lock);
+	em = lookup_extent_mapping(em_tree, logical, len);
+	read_unlock(&em_tree->lock);
+	BUG_ON(!em);
+
+	BUG_ON(em->start > logical || em->start + em->len < logical);
+	map = (struct map_lookup *)em->bdev;
+	if (map->type & (BTRFS_BLOCK_GROUP_RAID5 |
+			 BTRFS_BLOCK_GROUP_RAID6))
+		ret = 1;
+	free_extent_map(em);
+	return ret;
+}
+
 static int find_live_mirror(struct btrfs_fs_info *fs_info,
 			    struct map_lookup *map, int first, int num,
 			    int optimal, int dev_replace_is_ongoing)
@@ -4185,10 +4314,39 @@
 	return optimal;
 }
 
+static inline int parity_smaller(u64 a, u64 b)
+{
+	return a > b;
+}
+
+/* Bubble-sort the stripe set to put the parity/syndrome stripes last */
+static void sort_parity_stripes(struct btrfs_bio *bbio, u64 *raid_map)
+{
+	struct btrfs_bio_stripe s;
+	int i;
+	u64 l;
+	int again = 1;
+
+	while (again) {
+		again = 0;
+		for (i = 0; i < bbio->num_stripes - 1; i++) {
+			if (parity_smaller(raid_map[i], raid_map[i+1])) {
+				s = bbio->stripes[i];
+				l = raid_map[i];
+				bbio->stripes[i] = bbio->stripes[i+1];
+				raid_map[i] = raid_map[i+1];
+				bbio->stripes[i+1] = s;
+				raid_map[i+1] = l;
+				again = 1;
+			}
+		}
+	}
+}
+
 static int __btrfs_map_block(struct btrfs_fs_info *fs_info, int rw,
 			     u64 logical, u64 *length,
 			     struct btrfs_bio **bbio_ret,
-			     int mirror_num)
+			     int mirror_num, u64 **raid_map_ret)
 {
 	struct extent_map *em;
 	struct map_lookup *map;
@@ -4200,6 +4358,8 @@
 	u64 stripe_nr;
 	u64 stripe_nr_orig;
 	u64 stripe_nr_end;
+	u64 stripe_len;
+	u64 *raid_map = NULL;
 	int stripe_index;
 	int i;
 	int ret = 0;
@@ -4211,6 +4371,7 @@
 	int num_alloc_stripes;
 	int patch_the_first_stripe_for_dev_replace = 0;
 	u64 physical_to_patch_in_first_stripe = 0;
+	u64 raid56_full_stripe_start = (u64)-1;
 
 	read_lock(&em_tree->lock);
 	em = lookup_extent_mapping(em_tree, logical, *length);
@@ -4227,29 +4388,63 @@
 	map = (struct map_lookup *)em->bdev;
 	offset = logical - em->start;
 
+	if (mirror_num > map->num_stripes)
+		mirror_num = 0;
+
+	stripe_len = map->stripe_len;
 	stripe_nr = offset;
 	/*
 	 * stripe_nr counts the total number of stripes we have to stride
 	 * to get to this block
 	 */
-	do_div(stripe_nr, map->stripe_len);
+	do_div(stripe_nr, stripe_len);
 
-	stripe_offset = stripe_nr * map->stripe_len;
+	stripe_offset = stripe_nr * stripe_len;
 	BUG_ON(offset < stripe_offset);
 
 	/* stripe_offset is the offset of this block in its stripe*/
 	stripe_offset = offset - stripe_offset;
 
-	if (rw & REQ_DISCARD)
+	/* if we're here for raid56, we need to know the stripe aligned start */
+	if (map->type & (BTRFS_BLOCK_GROUP_RAID5 | BTRFS_BLOCK_GROUP_RAID6)) {
+		unsigned long full_stripe_len = stripe_len * nr_data_stripes(map);
+		raid56_full_stripe_start = offset;
+
+		/* allow a write of a full stripe, but make sure we don't
+		 * allow straddling of stripes
+		 */
+		do_div(raid56_full_stripe_start, full_stripe_len);
+		raid56_full_stripe_start *= full_stripe_len;
+	}
+
+	if (rw & REQ_DISCARD) {
+		/* we don't discard raid56 yet */
+		if (map->type &
+		    (BTRFS_BLOCK_GROUP_RAID5 | BTRFS_BLOCK_GROUP_RAID6)) {
+			ret = -EOPNOTSUPP;
+			goto out;
+		}
 		*length = min_t(u64, em->len - offset, *length);
-	else if (map->type & BTRFS_BLOCK_GROUP_PROFILE_MASK) {
-		/* we limit the length of each bio to what fits in a stripe */
-		*length = min_t(u64, em->len - offset,
-				map->stripe_len - stripe_offset);
+	} else if (map->type & BTRFS_BLOCK_GROUP_PROFILE_MASK) {
+		u64 max_len;
+		/* For writes to RAID[56], allow a full stripeset across all disks.
+		   For other RAID types and for RAID[56] reads, just allow a single
+		   stripe (on a single disk). */
+		if (map->type & (BTRFS_BLOCK_GROUP_RAID5 | BTRFS_BLOCK_GROUP_RAID6) &&
+		    (rw & REQ_WRITE)) {
+			max_len = stripe_len * nr_data_stripes(map) -
+				(offset - raid56_full_stripe_start);
+		} else {
+			/* we limit the length of each bio to what fits in a stripe */
+			max_len = stripe_len - stripe_offset;
+		}
+		*length = min_t(u64, em->len - offset, max_len);
 	} else {
 		*length = em->len - offset;
 	}
 
+	/* This is for when we're called from btrfs_merge_bio_hook() and all
+	   it cares about is the length */
 	if (!bbio_ret)
 		goto out;
 
@@ -4282,7 +4477,7 @@
 		u64 physical_of_found = 0;
 
 		ret = __btrfs_map_block(fs_info, REQ_GET_READ_MIRRORS,
-			     logical, &tmp_length, &tmp_bbio, 0);
+			     logical, &tmp_length, &tmp_bbio, 0, NULL);
 		if (ret) {
 			WARN_ON(tmp_bbio != NULL);
 			goto out;
@@ -4348,6 +4543,7 @@
 	do_div(stripe_nr_end, map->stripe_len);
 	stripe_end_offset = stripe_nr_end * map->stripe_len -
 			    (offset + *length);
+
 	if (map->type & BTRFS_BLOCK_GROUP_RAID0) {
 		if (rw & REQ_DISCARD)
 			num_stripes = min_t(u64, map->num_stripes,
@@ -4398,6 +4594,65 @@
 					      dev_replace_is_ongoing);
 			mirror_num = stripe_index - old_stripe_index + 1;
 		}
+
+	} else if (map->type & (BTRFS_BLOCK_GROUP_RAID5 |
+				BTRFS_BLOCK_GROUP_RAID6)) {
+		u64 tmp;
+
+		if (bbio_ret && ((rw & REQ_WRITE) || mirror_num > 1)
+		    && raid_map_ret) {
+			int i, rot;
+
+			/* push stripe_nr back to the start of the full stripe */
+			stripe_nr = raid56_full_stripe_start;
+			do_div(stripe_nr, stripe_len);
+
+			stripe_index = do_div(stripe_nr, nr_data_stripes(map));
+
+			/* RAID[56] write or recovery. Return all stripes */
+			num_stripes = map->num_stripes;
+			max_errors = nr_parity_stripes(map);
+
+			raid_map = kmalloc(sizeof(u64) * num_stripes,
+					   GFP_NOFS);
+			if (!raid_map) {
+				ret = -ENOMEM;
+				goto out;
+			}
+
+			/* Work out the disk rotation on this stripe-set */
+			tmp = stripe_nr;
+			rot = do_div(tmp, num_stripes);
+
+			/* Fill in the logical address of each stripe */
+			tmp = stripe_nr * nr_data_stripes(map);
+			for (i = 0; i < nr_data_stripes(map); i++)
+				raid_map[(i+rot) % num_stripes] =
+					em->start + (tmp + i) * map->stripe_len;
+
+			raid_map[(i+rot) % map->num_stripes] = RAID5_P_STRIPE;
+			if (map->type & BTRFS_BLOCK_GROUP_RAID6)
+				raid_map[(i+rot+1) % num_stripes] =
+					RAID6_Q_STRIPE;
+
+			*length = map->stripe_len;
+			stripe_index = 0;
+			stripe_offset = 0;
+		} else {
+			/*
+			 * Mirror #0 or #1 means the original data block.
+			 * Mirror #2 is RAID5 parity block.
+			 * Mirror #3 is RAID6 Q block.
+			 */
+			stripe_index = do_div(stripe_nr, nr_data_stripes(map));
+			if (mirror_num > 1)
+				stripe_index = nr_data_stripes(map) +
+						mirror_num - 2;
+
+			/* We distribute the parity blocks across stripes */
+			tmp = stripe_nr + stripe_index;
+			stripe_index = do_div(tmp, map->num_stripes);
+		}
 	} else {
 		/*
 		 * after this do_div call, stripe_nr is the number of stripes
@@ -4506,8 +4761,11 @@
 	if (rw & (REQ_WRITE | REQ_GET_READ_MIRRORS)) {
 		if (map->type & (BTRFS_BLOCK_GROUP_RAID1 |
 				 BTRFS_BLOCK_GROUP_RAID10 |
+				 BTRFS_BLOCK_GROUP_RAID5 |
 				 BTRFS_BLOCK_GROUP_DUP)) {
 			max_errors = 1;
+		} else if (map->type & BTRFS_BLOCK_GROUP_RAID6) {
+			max_errors = 2;
 		}
 	}
 
@@ -4608,6 +4866,10 @@
 		bbio->stripes[0].physical = physical_to_patch_in_first_stripe;
 		bbio->mirror_num = map->num_stripes + 1;
 	}
+	if (raid_map) {
+		sort_parity_stripes(bbio, raid_map);
+		*raid_map_ret = raid_map;
+	}
 out:
 	if (dev_replace_is_ongoing)
 		btrfs_dev_replace_unlock(dev_replace);
@@ -4620,7 +4882,7 @@
 		      struct btrfs_bio **bbio_ret, int mirror_num)
 {
 	return __btrfs_map_block(fs_info, rw, logical, length, bbio_ret,
-				 mirror_num);
+				 mirror_num, NULL);
 }
 
 int btrfs_rmap_block(struct btrfs_mapping_tree *map_tree,
@@ -4634,6 +4896,7 @@
 	u64 bytenr;
 	u64 length;
 	u64 stripe_nr;
+	u64 rmap_len;
 	int i, j, nr = 0;
 
 	read_lock(&em_tree->lock);
@@ -4644,10 +4907,17 @@
 	map = (struct map_lookup *)em->bdev;
 
 	length = em->len;
+	rmap_len = map->stripe_len;
+
 	if (map->type & BTRFS_BLOCK_GROUP_RAID10)
 		do_div(length, map->num_stripes / map->sub_stripes);
 	else if (map->type & BTRFS_BLOCK_GROUP_RAID0)
 		do_div(length, map->num_stripes);
+	else if (map->type & (BTRFS_BLOCK_GROUP_RAID5 |
+			      BTRFS_BLOCK_GROUP_RAID6)) {
+		do_div(length, nr_data_stripes(map));
+		rmap_len = map->stripe_len * nr_data_stripes(map);
+	}
 
 	buf = kzalloc(sizeof(u64) * map->num_stripes, GFP_NOFS);
 	BUG_ON(!buf); /* -ENOMEM */
@@ -4667,8 +4937,11 @@
 			do_div(stripe_nr, map->sub_stripes);
 		} else if (map->type & BTRFS_BLOCK_GROUP_RAID0) {
 			stripe_nr = stripe_nr * map->num_stripes + i;
-		}
-		bytenr = chunk_start + stripe_nr * map->stripe_len;
+		} /* else if RAID[56], multiply by nr_data_stripes().
+		   * Alternatively, just use rmap_len below instead of
+		   * map->stripe_len */
+
+		bytenr = chunk_start + stripe_nr * rmap_len;
 		WARN_ON(nr >= map->num_stripes);
 		for (j = 0; j < nr; j++) {
 			if (buf[j] == bytenr)
@@ -4682,7 +4955,7 @@
 
 	*logical = buf;
 	*naddrs = nr;
-	*stripe_len = map->stripe_len;
+	*stripe_len = rmap_len;
 
 	free_extent_map(em);
 	return 0;
@@ -4756,7 +5029,7 @@
 		bio->bi_bdev = (struct block_device *)
 					(unsigned long)bbio->mirror_num;
 		/* only send an error to the higher layers if it is
-		 * beyond the tolerance of the multi-bio
+		 * beyond the tolerance of the btrfs bio
 		 */
 		if (atomic_read(&bbio->error) > bbio->max_errors) {
 			err = -EIO;
@@ -4790,13 +5063,18 @@
  * This will add one bio to the pending list for a device and make sure
  * the work struct is scheduled.
  */
-static noinline void schedule_bio(struct btrfs_root *root,
+noinline void btrfs_schedule_bio(struct btrfs_root *root,
 				 struct btrfs_device *device,
 				 int rw, struct bio *bio)
 {
 	int should_queue = 1;
 	struct btrfs_pending_bios *pending_bios;
 
+	if (device->missing || !device->bdev) {
+		bio_endio(bio, -EIO);
+		return;
+	}
+
 	/* don't bother with additional async steps for reads, right now */
 	if (!(rw & REQ_WRITE)) {
 		bio_get(bio);
@@ -4894,7 +5172,7 @@
 #endif
 	bio->bi_bdev = dev->bdev;
 	if (async)
-		schedule_bio(root, dev, rw, bio);
+		btrfs_schedule_bio(root, dev, rw, bio);
 	else
 		btrfsic_submit_bio(rw, bio);
 }
@@ -4953,6 +5231,7 @@
 	u64 logical = (u64)bio->bi_sector << 9;
 	u64 length = 0;
 	u64 map_length;
+	u64 *raid_map = NULL;
 	int ret;
 	int dev_nr = 0;
 	int total_devs = 1;
@@ -4961,12 +5240,30 @@
 	length = bio->bi_size;
 	map_length = length;
 
-	ret = btrfs_map_block(root->fs_info, rw, logical, &map_length, &bbio,
-			      mirror_num);
-	if (ret)
+	ret = __btrfs_map_block(root->fs_info, rw, logical, &map_length, &bbio,
+			      mirror_num, &raid_map);
+	if (ret) /* -ENOMEM */
 		return ret;
 
 	total_devs = bbio->num_stripes;
+	bbio->orig_bio = first_bio;
+	bbio->private = first_bio->bi_private;
+	bbio->end_io = first_bio->bi_end_io;
+	atomic_set(&bbio->stripes_pending, bbio->num_stripes);
+
+	if (raid_map) {
+		/* In this case, map_length has been set to the length of
+		   a single stripe; not the whole write */
+		if (rw & WRITE) {
+			return raid56_parity_write(root, bio, bbio,
+						   raid_map, map_length);
+		} else {
+			return raid56_parity_recover(root, bio, bbio,
+						     raid_map, map_length,
+						     mirror_num);
+		}
+	}
+
 	if (map_length < length) {
 		printk(KERN_CRIT "btrfs: mapping failed logical %llu bio len %llu "
 		       "len %llu\n", (unsigned long long)logical,
@@ -4975,11 +5272,6 @@
 		BUG();
 	}
 
-	bbio->orig_bio = first_bio;
-	bbio->private = first_bio->bi_private;
-	bbio->end_io = first_bio->bi_end_io;
-	atomic_set(&bbio->stripes_pending, bbio->num_stripes);
-
 	while (dev_nr < total_devs) {
 		dev = bbio->stripes[dev_nr].dev;
 		if (!dev || !dev->bdev || (rw & WRITE && !dev->writeable)) {
diff --git a/fs/btrfs/volumes.h b/fs/btrfs/volumes.h
index 12bb841..062d860 100644
--- a/fs/btrfs/volumes.h
+++ b/fs/btrfs/volumes.h
@@ -321,7 +321,14 @@
 void btrfs_init_dev_replace_tgtdev_for_resume(struct btrfs_fs_info *fs_info,
 					      struct btrfs_device *tgtdev);
 int btrfs_scratch_superblock(struct btrfs_device *device);
-
+void btrfs_schedule_bio(struct btrfs_root *root,
+			struct btrfs_device *device,
+			int rw, struct bio *bio);
+int btrfs_is_parity_mirror(struct btrfs_mapping_tree *map_tree,
+			   u64 logical, u64 len, int mirror_num);
+unsigned long btrfs_full_stripe_len(struct btrfs_root *root,
+				    struct btrfs_mapping_tree *map_tree,
+				    u64 logical);
 static inline void btrfs_dev_stat_inc(struct btrfs_device *dev,
 				      int index)
 {