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authorRaz Ben-Jehuda(caro) <raziebe@gmail.com>2006-12-10 02:20:47 -0800
committerLinus Torvalds <torvalds@woody.osdl.org>2006-12-10 09:57:20 -0800
commit46031f9a38a9773021f1872abc713d62467ac22e (patch)
treefe91f661fe0aad5f149447797c5d31544453ca38 /drivers/md
parentf679623f50545bc0577caf2d0f8675b61162f059 (diff)
[PATCH] md: allow reads that have bypassed the cache to be retried on failure
If a bypass-the-cache read fails, we simply try again through the cache. If it fails again it will trigger normal recovery precedures. update 1: From: NeilBrown <neilb@suse.de> 1/ chunk_aligned_read and retry_aligned_read assume that data_disks == raid_disks - 1 which is not true for raid6. So when an aligned read request bypasses the cache, we can get the wrong data. 2/ The cloned bio is being used-after-free in raid5_align_endio (to test BIO_UPTODATE). 3/ We forgot to add rdev->data_offset when submitting a bio for aligned-read 4/ clone_bio calls blk_recount_segments and then we change bi_bdev, so we need to invalidate the segment counts. 5/ We don't de-reference the rdev when the read completes. This means we need to record the rdev to so it is still available in the end_io routine. Fortunately bi_next in the original bio is unused at this point so we can stuff it in there. 6/ We leak a cloned bio if the target rdev is not usable. From: NeilBrown <neilb@suse.de> update 2: 1/ When aligned requests fail (read error) they need to be retried via the normal method (stripe cache). As we cannot be sure that we can process a single read in one go (we may not be able to allocate all the stripes needed) we store a bio-being-retried and a list of bioes-that-still-need-to-be-retried. When find a bio that needs to be retried, we should add it to the list, not to single-bio... 2/ We were never incrementing 'scnt' when resubmitting failed aligned requests. [akpm@osdl.org: build fix] Signed-off-by: Neil Brown <neilb@suse.de> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
Diffstat (limited to 'drivers/md')
-rw-r--r--drivers/md/raid5.c165
1 files changed, 160 insertions, 5 deletions
diff --git a/drivers/md/raid5.c b/drivers/md/raid5.c
index 269b7771a30..2ac2e56a1a4 100644
--- a/drivers/md/raid5.c
+++ b/drivers/md/raid5.c
@@ -134,6 +134,8 @@ static void __release_stripe(raid5_conf_t *conf, struct stripe_head *sh)
if (!test_bit(STRIPE_EXPANDING, &sh->state)) {
list_add_tail(&sh->lru, &conf->inactive_list);
wake_up(&conf->wait_for_stripe);
+ if (conf->retry_read_aligned)
+ md_wakeup_thread(conf->mddev->thread);
}
}
}
@@ -2645,18 +2647,80 @@ static int in_chunk_boundary(mddev_t *mddev, struct bio *bio)
}
/*
+ * add bio to the retry LIFO ( in O(1) ... we are in interrupt )
+ * later sampled by raid5d.
+ */
+static void add_bio_to_retry(struct bio *bi,raid5_conf_t *conf)
+{
+ unsigned long flags;
+
+ spin_lock_irqsave(&conf->device_lock, flags);
+
+ bi->bi_next = conf->retry_read_aligned_list;
+ conf->retry_read_aligned_list = bi;
+
+ spin_unlock_irqrestore(&conf->device_lock, flags);
+ md_wakeup_thread(conf->mddev->thread);
+}
+
+
+static struct bio *remove_bio_from_retry(raid5_conf_t *conf)
+{
+ struct bio *bi;
+
+ bi = conf->retry_read_aligned;
+ if (bi) {
+ conf->retry_read_aligned = NULL;
+ return bi;
+ }
+ bi = conf->retry_read_aligned_list;
+ if(bi) {
+ conf->retry_read_aligned = bi->bi_next;
+ bi->bi_next = NULL;
+ bi->bi_phys_segments = 1; /* biased count of active stripes */
+ bi->bi_hw_segments = 0; /* count of processed stripes */
+ }
+
+ return bi;
+}
+
+
+/*
* The "raid5_align_endio" should check if the read succeeded and if it
* did, call bio_endio on the original bio (having bio_put the new bio
* first).
* If the read failed..
*/
-int raid5_align_endio(struct bio *bi, unsigned int bytes , int error)
+static int raid5_align_endio(struct bio *bi, unsigned int bytes, int error)
{
struct bio* raid_bi = bi->bi_private;
+ mddev_t *mddev;
+ raid5_conf_t *conf;
+ int uptodate = test_bit(BIO_UPTODATE, &bi->bi_flags);
+ mdk_rdev_t *rdev;
+
if (bi->bi_size)
return 1;
bio_put(bi);
- bio_endio(raid_bi, bytes, error);
+
+ mddev = raid_bi->bi_bdev->bd_disk->queue->queuedata;
+ conf = mddev_to_conf(mddev);
+ rdev = (void*)raid_bi->bi_next;
+ raid_bi->bi_next = NULL;
+
+ rdev_dec_pending(rdev, conf->mddev);
+
+ if (!error && uptodate) {
+ bio_endio(raid_bi, bytes, 0);
+ if (atomic_dec_and_test(&conf->active_aligned_reads))
+ wake_up(&conf->wait_for_stripe);
+ return 0;
+ }
+
+
+ PRINTK("raid5_align_endio : io error...handing IO for a retry\n");
+
+ add_bio_to_retry(raid_bi, conf);
return 0;
}
@@ -2665,7 +2729,7 @@ static int chunk_aligned_read(request_queue_t *q, struct bio * raid_bio)
mddev_t *mddev = q->queuedata;
raid5_conf_t *conf = mddev_to_conf(mddev);
const unsigned int raid_disks = conf->raid_disks;
- const unsigned int data_disks = raid_disks - 1;
+ const unsigned int data_disks = raid_disks - conf->max_degraded;
unsigned int dd_idx, pd_idx;
struct bio* align_bi;
mdk_rdev_t *rdev;
@@ -2699,13 +2763,25 @@ static int chunk_aligned_read(request_queue_t *q, struct bio * raid_bio)
rcu_read_lock();
rdev = rcu_dereference(conf->disks[dd_idx].rdev);
if (rdev && test_bit(In_sync, &rdev->flags)) {
- align_bi->bi_bdev = rdev->bdev;
atomic_inc(&rdev->nr_pending);
rcu_read_unlock();
+ raid_bio->bi_next = (void*)rdev;
+ align_bi->bi_bdev = rdev->bdev;
+ align_bi->bi_flags &= ~(1 << BIO_SEG_VALID);
+ align_bi->bi_sector += rdev->data_offset;
+
+ spin_lock_irq(&conf->device_lock);
+ wait_event_lock_irq(conf->wait_for_stripe,
+ conf->quiesce == 0,
+ conf->device_lock, /* nothing */);
+ atomic_inc(&conf->active_aligned_reads);
+ spin_unlock_irq(&conf->device_lock);
+
generic_make_request(align_bi);
return 1;
} else {
rcu_read_unlock();
+ bio_put(align_bi);
return 0;
}
}
@@ -3050,6 +3126,72 @@ static inline sector_t sync_request(mddev_t *mddev, sector_t sector_nr, int *ski
return STRIPE_SECTORS;
}
+static int retry_aligned_read(raid5_conf_t *conf, struct bio *raid_bio)
+{
+ /* We may not be able to submit a whole bio at once as there
+ * may not be enough stripe_heads available.
+ * We cannot pre-allocate enough stripe_heads as we may need
+ * more than exist in the cache (if we allow ever large chunks).
+ * So we do one stripe head at a time and record in
+ * ->bi_hw_segments how many have been done.
+ *
+ * We *know* that this entire raid_bio is in one chunk, so
+ * it will be only one 'dd_idx' and only need one call to raid5_compute_sector.
+ */
+ struct stripe_head *sh;
+ int dd_idx, pd_idx;
+ sector_t sector, logical_sector, last_sector;
+ int scnt = 0;
+ int remaining;
+ int handled = 0;
+
+ logical_sector = raid_bio->bi_sector & ~((sector_t)STRIPE_SECTORS-1);
+ sector = raid5_compute_sector( logical_sector,
+ conf->raid_disks,
+ conf->raid_disks - conf->max_degraded,
+ &dd_idx,
+ &pd_idx,
+ conf);
+ last_sector = raid_bio->bi_sector + (raid_bio->bi_size>>9);
+
+ for (; logical_sector < last_sector;
+ logical_sector += STRIPE_SECTORS, scnt++) {
+
+ if (scnt < raid_bio->bi_hw_segments)
+ /* already done this stripe */
+ continue;
+
+ sh = get_active_stripe(conf, sector, conf->raid_disks, pd_idx, 1);
+
+ if (!sh) {
+ /* failed to get a stripe - must wait */
+ raid_bio->bi_hw_segments = scnt;
+ conf->retry_read_aligned = raid_bio;
+ return handled;
+ }
+
+ set_bit(R5_ReadError, &sh->dev[dd_idx].flags);
+ add_stripe_bio(sh, raid_bio, dd_idx, 0);
+ handle_stripe(sh, NULL);
+ release_stripe(sh);
+ handled++;
+ }
+ spin_lock_irq(&conf->device_lock);
+ remaining = --raid_bio->bi_phys_segments;
+ spin_unlock_irq(&conf->device_lock);
+ if (remaining == 0) {
+ int bytes = raid_bio->bi_size;
+
+ raid_bio->bi_size = 0;
+ raid_bio->bi_end_io(raid_bio, bytes, 0);
+ }
+ if (atomic_dec_and_test(&conf->active_aligned_reads))
+ wake_up(&conf->wait_for_stripe);
+ return handled;
+}
+
+
+
/*
* This is our raid5 kernel thread.
*
@@ -3071,6 +3213,7 @@ static void raid5d (mddev_t *mddev)
spin_lock_irq(&conf->device_lock);
while (1) {
struct list_head *first;
+ struct bio *bio;
if (conf->seq_flush != conf->seq_write) {
int seq = conf->seq_flush;
@@ -3087,6 +3230,16 @@ static void raid5d (mddev_t *mddev)
!list_empty(&conf->delayed_list))
raid5_activate_delayed(conf);
+ while ((bio = remove_bio_from_retry(conf))) {
+ int ok;
+ spin_unlock_irq(&conf->device_lock);
+ ok = retry_aligned_read(conf, bio);
+ spin_lock_irq(&conf->device_lock);
+ if (!ok)
+ break;
+ handled++;
+ }
+
if (list_empty(&conf->handle_list))
break;
@@ -3274,6 +3427,7 @@ static int run(mddev_t *mddev)
INIT_LIST_HEAD(&conf->inactive_list);
atomic_set(&conf->active_stripes, 0);
atomic_set(&conf->preread_active_stripes, 0);
+ atomic_set(&conf->active_aligned_reads, 0);
PRINTK("raid5: run(%s) called.\n", mdname(mddev));
@@ -3796,7 +3950,8 @@ static void raid5_quiesce(mddev_t *mddev, int state)
spin_lock_irq(&conf->device_lock);
conf->quiesce = 1;
wait_event_lock_irq(conf->wait_for_stripe,
- atomic_read(&conf->active_stripes) == 0,
+ atomic_read(&conf->active_stripes) == 0 &&
+ atomic_read(&conf->active_aligned_reads) == 0,
conf->device_lock, /* nothing */);
spin_unlock_irq(&conf->device_lock);
break;