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Message-Id: <1061031060108.5095@suse.de>
Date: Tue, 31 Oct 2006 17:01:08 +1100
From: NeilBrown <neilb@...e.de>
To: Andrew Morton <akpm@...l.org>
Cc: "Raz Ben-Jehuda(caro)" <raziebe@...il.com>
Subject: [PATCH 005 of 6] 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.
cc: "Raz Ben-Jehuda(caro)" <raziebe@...il.com>
Signed-off-by: Neil Brown <neilb@...e.de>
### Diffstat output
./drivers/md/raid5.c | 150 ++++++++++++++++++++++++++++++++++++++++++-
./include/linux/raid/raid5.h | 3
2 files changed, 150 insertions(+), 3 deletions(-)
diff .prev/drivers/md/raid5.c ./drivers/md/raid5.c
--- .prev/drivers/md/raid5.c 2006-10-31 16:41:51.000000000 +1100
+++ ./drivers/md/raid5.c 2006-10-31 16:42:30.000000000 +1100
@@ -134,6 +134,8 @@ static void __release_stripe(raid5_conf_
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 +2647,74 @@ static int in_chunk_boundary(mddev_t *md
}
/*
+ * 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;
+ conf->retry_read_aligned = 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)
+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;
+
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);
+
+ if (!error && test_bit(BIO_UPTODATE, &bi->bi_flags)) {
+ 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;
}
@@ -2702,6 +2760,14 @@ static int chunk_aligned_read(request_qu
align_bi->bi_bdev = rdev->bdev;
atomic_inc(&rdev->nr_pending);
rcu_read_unlock();
+
+ 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 {
@@ -3050,6 +3116,71 @@ static inline sector_t sync_request(mdde
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-1,
+ &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) {
+
+ 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 +3202,7 @@ 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 +3219,16 @@ 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 +3416,7 @@ 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 +3939,8 @@ static void raid5_quiesce(mddev_t *mddev
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;
diff .prev/include/linux/raid/raid5.h ./include/linux/raid/raid5.h
--- .prev/include/linux/raid/raid5.h 2006-10-31 16:40:56.000000000 +1100
+++ ./include/linux/raid/raid5.h 2006-10-31 16:42:30.000000000 +1100
@@ -227,7 +227,10 @@ struct raid5_private_data {
struct list_head handle_list; /* stripes needing handling */
struct list_head delayed_list; /* stripes that have plugged requests */
struct list_head bitmap_list; /* stripes delaying awaiting bitmap update */
+ struct bio *retry_read_aligned; /* currently retrying aligned bios */
+ struct bio *retry_read_aligned_list; /* aligned bios retry list */
atomic_t preread_active_stripes; /* stripes with scheduled io */
+ atomic_t active_aligned_reads;
atomic_t reshape_stripes; /* stripes with pending writes for reshape */
/* unfortunately we need two cache names as we temporarily have
-
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