Revert "md/raid10: improve discard request for far layout"

This reverts commit d3ee2d8415a6256c1c41e1be36e80e640c3e6359.

Matthew Ruffell reported data corruption in raid10 due to the changes
in discard handling [1]. Revert these changes before we find a proper fix.

[1] https://bugs.launchpad.net/ubuntu/+source/linux/+bug/1907262/
Cc: Matthew Ruffell <matthew.ruffell@canonical.com>
Cc: Xiao Ni <xni@redhat.com>
Signed-off-by: Song Liu <songliubraving@fb.com>

diff --git a/drivers/md/raid10.c b/drivers/md/raid10.c
index b7bca67..05773ee 100644 (file)
--- a/drivers/md/raid10.c
+++ b/drivers/md/raid10.c
@@ -1534,28 +1534,6 @@ static struct bio *raid10_split_bio(struct r10conf *conf,
        return bio;
 }
 
-static void raid_end_discard_bio(struct r10bio *r10bio)
-{
-       struct r10conf *conf = r10bio->mddev->private;
-       struct r10bio *first_r10bio;
-
-       while (atomic_dec_and_test(&r10bio->remaining)) {
-
-               allow_barrier(conf);
-
-               if (!test_bit(R10BIO_Discard, &r10bio->state)) {
-                       first_r10bio = (struct r10bio *)r10bio->master_bio;
-                       free_r10bio(r10bio);
-                       r10bio = first_r10bio;
-               } else {
-                       md_write_end(r10bio->mddev);
-                       bio_endio(r10bio->master_bio);
-                       free_r10bio(r10bio);
-                       break;
-               }
-       }
-}
-
 static void raid10_end_discard_request(struct bio *bio)
 {
        struct r10bio *r10_bio = bio->bi_private;
@@ -1582,7 +1560,11 @@ static void raid10_end_discard_request(struct bio *bio)
                rdev = conf->mirrors[dev].rdev;
        }
 
-       raid_end_discard_bio(r10_bio);
+       if (atomic_dec_and_test(&r10_bio->remaining)) {
+               md_write_end(r10_bio->mddev);
+               raid_end_bio_io(r10_bio);
+       }
+
        rdev_dec_pending(rdev, conf->mddev);
 }
 
@@ -1595,9 +1577,7 @@ static int raid10_handle_discard(struct mddev *mddev, struct bio *bio)
 {
        struct r10conf *conf = mddev->private;
        struct geom *geo = &conf->geo;
-       struct r10bio *r10_bio, *first_r10bio;
-       int far_copies = geo->far_copies;
-       bool first_copy = true;
+       struct r10bio *r10_bio;
 
        int disk;
        sector_t chunk;
@@ -1636,20 +1616,30 @@ static int raid10_handle_discard(struct mddev *mddev, struct bio *bio)
        if (bio_sectors(bio) < stripe_size*2)
                goto out;
 
-       /* For far and far offset layout, if bio is not aligned with stripe size,
-        * it splits the part that is not aligned with strip size.
+       /* For far offset layout, if bio is not aligned with stripe size, it splits
+        * the part that is not aligned with strip size.
         */
        div_u64_rem(bio_start, stripe_size, &remainder);
-       if ((far_copies > 1) && remainder) {
+       if (geo->far_offset && remainder) {
                split_size = stripe_size - remainder;
                bio = raid10_split_bio(conf, bio, split_size, false);
        }
        div_u64_rem(bio_end, stripe_size, &remainder);
-       if ((far_copies > 1) && remainder) {
+       if (geo->far_offset && remainder) {
                split_size = bio_sectors(bio) - remainder;
                bio = raid10_split_bio(conf, bio, split_size, true);
        }
 
+       r10_bio = mempool_alloc(&conf->r10bio_pool, GFP_NOIO);
+       r10_bio->mddev = mddev;
+       r10_bio->state = 0;
+       r10_bio->sectors = 0;
+       memset(r10_bio->devs, 0, sizeof(r10_bio->devs[0]) * geo->raid_disks);
+
+       wait_blocked_dev(mddev, r10_bio);
+
+       r10_bio->master_bio = bio;
+
        bio_start = bio->bi_iter.bi_sector;
        bio_end = bio_end_sector(bio);
 
@@ -1675,28 +1665,6 @@ static int raid10_handle_discard(struct mddev *mddev, struct bio *bio)
        end_disk_offset = (bio_end & geo->chunk_mask) +
                                (last_stripe_index << geo->chunk_shift);
 
-retry_discard:
-       r10_bio = mempool_alloc(&conf->r10bio_pool, GFP_NOIO);
-       r10_bio->mddev = mddev;
-       r10_bio->state = 0;
-       r10_bio->sectors = 0;
-       memset(r10_bio->devs, 0, sizeof(r10_bio->devs[0]) * geo->raid_disks);
-       wait_blocked_dev(mddev, r10_bio);
-
-       /* For far layout it needs more than one r10bio to cover all regions.
-        * Inspired by raid10_sync_request, we can use the first r10bio->master_bio
-        * to record the discard bio. Other r10bio->master_bio record the first
-        * r10bio. The first r10bio only release after all other r10bios finish.
-        * The discard bio returns only first r10bio finishes
-        */
-       if (first_copy) {
-               r10_bio->master_bio = bio;
-               set_bit(R10BIO_Discard, &r10_bio->state);
-               first_copy = false;
-               first_r10bio = r10_bio;
-       } else
-               r10_bio->master_bio = (struct bio *)first_r10bio;
-
        rcu_read_lock();
        for (disk = 0; disk < geo->raid_disks; disk++) {
                struct md_rdev *rdev = rcu_dereference(conf->mirrors[disk].rdev);
@@ -1787,19 +1755,11 @@ retry_discard:
                }
        }
 
-       if (!geo->far_offset && --far_copies) {
-               first_stripe_index += geo->stride >> geo->chunk_shift;
-               start_disk_offset += geo->stride;
-               last_stripe_index += geo->stride >> geo->chunk_shift;
-               end_disk_offset += geo->stride;
-               atomic_inc(&first_r10bio->remaining);
-               raid_end_discard_bio(r10_bio);
-               wait_barrier(conf);
-               goto retry_discard;
+       if (atomic_dec_and_test(&r10_bio->remaining)) {
+               md_write_end(r10_bio->mddev);
+               raid_end_bio_io(r10_bio);
        }
 
-       raid_end_discard_bio(r10_bio);
-
        return 0;
 out:
        allow_barrier(conf);

diff --git a/drivers/md/raid10.h b/drivers/md/raid10.h
index 1461fd5..79cd2b7 100644 (file)
--- a/drivers/md/raid10.h
+++ b/drivers/md/raid10.h
@@ -179,6 +179,5 @@ enum r10bio_state {
        R10BIO_Previous,
 /* failfast devices did receive failfast requests. */
        R10BIO_FailFast,
-       R10BIO_Discard,
 };
 #endif