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authorLiu Bo <liubo2009@cn.fujitsu.com>2012-03-29 09:57:45 -0400
committerChris Mason <chris.mason@oracle.com>2012-03-29 09:57:45 -0400
commit17ce6ef8d731af5edac8c39e806db4c7e1f6956f (patch)
tree4a54d3c5618efff3deec03fa5d32a42c0a8fc804
parent4cb13e5d6ecc47b91b24a35f8fbc2c9f33d075fe (diff)
downloadlinux-linaro-stable-17ce6ef8d731af5edac8c39e806db4c7e1f6956f.tar.gz
Btrfs: add a check to decide if we should defrag the range
If our file's layout is as follows: | hole | data1 | hole | data2 | we do not need to defrag this file, because this file has holes and cannot be merged into one extent. Signed-off-by: Liu Bo <liubo2009@cn.fujitsu.com> Signed-off-by: Chris Mason <chris.mason@oracle.com>
-rw-r--r--fs/btrfs/ioctl.c36
1 files changed, 35 insertions, 1 deletions
diff --git a/fs/btrfs/ioctl.c b/fs/btrfs/ioctl.c
index de46fa218590..6c39d1a55907 100644
--- a/fs/btrfs/ioctl.c
+++ b/fs/btrfs/ioctl.c
@@ -784,6 +784,31 @@ none:
return -ENOENT;
}
+/*
+ * Validaty check of prev em and next em:
+ * 1) no prev/next em
+ * 2) prev/next em is an hole/inline extent
+ */
+static int check_adjacent_extents(struct inode *inode, struct extent_map *em)
+{
+ struct extent_map_tree *em_tree = &BTRFS_I(inode)->extent_tree;
+ struct extent_map *prev = NULL, *next = NULL;
+ int ret = 0;
+
+ read_lock(&em_tree->lock);
+ prev = lookup_extent_mapping(em_tree, em->start - 1, (u64)-1);
+ next = lookup_extent_mapping(em_tree, em->start + em->len, (u64)-1);
+ read_unlock(&em_tree->lock);
+
+ if ((!prev || prev->block_start >= EXTENT_MAP_LAST_BYTE) &&
+ (!next || next->block_start >= EXTENT_MAP_LAST_BYTE))
+ ret = 1;
+ free_extent_map(prev);
+ free_extent_map(next);
+
+ return ret;
+}
+
static int should_defrag_range(struct inode *inode, u64 start, u64 len,
int thresh, u64 *last_len, u64 *skip,
u64 *defrag_end)
@@ -821,8 +846,16 @@ static int should_defrag_range(struct inode *inode, u64 start, u64 len,
}
/* this will cover holes, and inline extents */
- if (em->block_start >= EXTENT_MAP_LAST_BYTE)
+ if (em->block_start >= EXTENT_MAP_LAST_BYTE) {
+ ret = 0;
+ goto out;
+ }
+
+ /* If we have nothing to merge with us, just skip. */
+ if (check_adjacent_extents(inode, em)) {
ret = 0;
+ goto out;
+ }
/*
* we hit a real extent, if it is big don't bother defragging it again
@@ -830,6 +863,7 @@ static int should_defrag_range(struct inode *inode, u64 start, u64 len,
if ((*last_len == 0 || *last_len >= thresh) && em->len >= thresh)
ret = 0;
+out:
/*
* last_len ends up being a counter of how many bytes we've defragged.
* every time we choose not to defrag an extent, we reset *last_len