md/raid10: improve discard request for far layout

For far layout, the discard region is not continuous on disks. So it needs
far copies r10bio to cover all regions. It needs a way to know all r10bios
have finish or not. Similar with raid10_sync_request, only the first r10bio
master_bio records the discard bio. Other r10bios master_bio record the
first r10bio. The first r10bio can finish after other r10bios finish and
then return the discard bio.

Tested-by: Adrian Huang <ahuang12@lenovo.com>
Signed-off-by: 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 2a61700..13f5e6b 100644 (file)
--- a/drivers/md/raid10.c
+++ b/drivers/md/raid10.c
@@ -1518,6 +1518,28 @@ static void __make_request(struct mddev *mddev, struct bio *bio, int sectors)
                raid10_write_request(mddev, bio, r10_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;
@@ -1545,11 +1567,7 @@ static void raid10_end_discard_request(struct bio *bio)
                rdev = conf->mirrors[dev].rdev;
        }
 
-       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);
        rdev_dec_pending(rdev, conf->mddev);
 }
 
@@ -1563,7 +1581,9 @@ 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;
+       int far_copies = geo->far_copies;
+       bool first_copy = true;
+       struct r10bio *r10_bio, *first_r10bio;
        struct bio *split;
        int disk;
        sector_t chunk;
@@ -1637,16 +1657,6 @@ static int raid10_handle_discard(struct mddev *mddev, struct bio *bio)
                wait_barrier(conf);
        }
 
-       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);
 
@@ -1673,6 +1683,29 @@ 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);
@@ -1764,11 +1797,19 @@ static int raid10_handle_discard(struct mddev *mddev, struct bio *bio)
                }
        }
 
-       if (atomic_dec_and_test(&r10_bio->remaining)) {
-               md_write_end(r10_bio->mddev);
-               raid_end_bio_io(r10_bio);
+       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;
        }
 
+       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 79cd2b7..1461fd5 100644 (file)
--- a/drivers/md/raid10.h
+++ b/drivers/md/raid10.h
@@ -179,5 +179,6 @@ enum r10bio_state {
        R10BIO_Previous,
 /* failfast devices did receive failfast requests. */
        R10BIO_FailFast,
+       R10BIO_Discard,
 };
 #endif