dm-raid456, md/raid456: fix a deadlock for dm-raid456 while io concurrent with reshape

For raid456, if reshape is still in progress, then IO across reshape
position will wait for reshape to make progress. However, for dm-raid,
in following cases reshape will never make progress hence IO will hang:

1) the array is read-only;
2) MD_RECOVERY_WAIT is set;
3) MD_RECOVERY_FROZEN is set;

After commit c467e97f079f ("md/raid6: use valid sector values to determine
if an I/O should wait on the reshape") fix the problem that IO across
reshape position doesn't wait for reshape, the dm-raid test
shell/lvconvert-raid-reshape.sh start to hang:

[root@fedora ~]# cat /proc/979/stack
[<0>] wait_woken+0x7d/0x90
[<0>] raid5_make_request+0x929/0x1d70 [raid456]
[<0>] md_handle_request+0xc2/0x3b0 [md_mod]
[<0>] raid_map+0x2c/0x50 [dm_raid]
[<0>] __map_bio+0x251/0x380 [dm_mod]
[<0>] dm_submit_bio+0x1f0/0x760 [dm_mod]
[<0>] __submit_bio+0xc2/0x1c0
[<0>] submit_bio_noacct_nocheck+0x17f/0x450
[<0>] submit_bio_noacct+0x2bc/0x780
[<0>] submit_bio+0x70/0xc0
[<0>] mpage_readahead+0x169/0x1f0
[<0>] blkdev_readahead+0x18/0x30
[<0>] read_pages+0x7c/0x3b0
[<0>] page_cache_ra_unbounded+0x1ab/0x280
[<0>] force_page_cache_ra+0x9e/0x130
[<0>] page_cache_sync_ra+0x3b/0x110
[<0>] filemap_get_pages+0x143/0xa30
[<0>] filemap_read+0xdc/0x4b0
[<0>] blkdev_read_iter+0x75/0x200
[<0>] vfs_read+0x272/0x460
[<0>] ksys_read+0x7a/0x170
[<0>] __x64_sys_read+0x1c/0x30
[<0>] do_syscall_64+0xc6/0x230
[<0>] entry_SYSCALL_64_after_hwframe+0x6c/0x74

This is because reshape can't make progress.

For md/raid, the problem doesn't exist because register new sync_thread
doesn't rely on the IO to be done any more:

1) If array is read-only, it can switch to read-write by ioctl/sysfs;
2) md/raid never set MD_RECOVERY_WAIT;
3) If MD_RECOVERY_FROZEN is set, mddev_suspend() doesn't hold
   'reconfig_mutex', hence it can be cleared and reshape can continue by
   sysfs api 'sync_action'.

However, I'm not sure yet how to avoid the problem in dm-raid yet. This
patch on the one hand make sure raid_message() can't change
sync_thread() through raid_message() after presuspend(), on the other
hand detect the above 3 cases before wait for IO do be done in
dm_suspend(), and let dm-raid requeue those IO.

Cc: stable@vger.kernel.org # v6.7+
Signed-off-by: Yu Kuai <yukuai3@huawei.com>
Signed-off-by: Xiao Ni <xni@redhat.com>
Acked-by: Mike Snitzer <snitzer@kernel.org>
Signed-off-by: Song Liu <song@kernel.org>
Link: https://lore.kernel.org/r/20240305072306.2562024-9-yukuai1@huaweicloud.com

diff --git a/drivers/md/dm-raid.c b/drivers/md/dm-raid.c
index 7d48943acd57cff286782e2f494a15240bae497d..ea45f777691cebe4f34b4885f3dd17dac502d793 100644 (file)
--- a/drivers/md/dm-raid.c
+++ b/drivers/md/dm-raid.c
@@ -213,6 +213,7 @@ struct raid_dev {
 #define RT_FLAG_RS_IN_SYNC             6
 #define RT_FLAG_RS_RESYNCING           7
 #define RT_FLAG_RS_GROW                        8
+#define RT_FLAG_RS_FROZEN              9
 
 /* Array elements of 64 bit needed for rebuild/failed disk bits */
 #define DISKS_ARRAY_ELEMS ((MAX_RAID_DEVICES + (sizeof(uint64_t) * 8 - 1)) / sizeof(uint64_t) / 8)
@@ -3340,7 +3341,8 @@ static int raid_map(struct dm_target *ti, struct bio *bio)
        if (unlikely(bio_end_sector(bio) > mddev->array_sectors))
                return DM_MAPIO_REQUEUE;
 
-       md_handle_request(mddev, bio);
+       if (unlikely(!md_handle_request(mddev, bio)))
+               return DM_MAPIO_REQUEUE;
 
        return DM_MAPIO_SUBMITTED;
 }
@@ -3724,7 +3726,8 @@ static int raid_message(struct dm_target *ti, unsigned int argc, char **argv,
        if (!mddev->pers || !mddev->pers->sync_request)
                return -EINVAL;
 
-       if (test_bit(RT_FLAG_RS_SUSPENDED, &rs->runtime_flags))
+       if (test_bit(RT_FLAG_RS_SUSPENDED, &rs->runtime_flags) ||
+           test_bit(RT_FLAG_RS_FROZEN, &rs->runtime_flags))
                return -EBUSY;
 
        if (!strcasecmp(argv[0], "frozen")) {
@@ -3808,6 +3811,12 @@ static void raid_presuspend(struct dm_target *ti)
        struct raid_set *rs = ti->private;
        struct mddev *mddev = &rs->md;
 
+       /*
+        * From now on, disallow raid_message() to change sync_thread until
+        * resume, raid_postsuspend() is too late.
+        */
+       set_bit(RT_FLAG_RS_FROZEN, &rs->runtime_flags);
+
        if (!reshape_interrupted(mddev))
                return;
 
@@ -3820,6 +3829,13 @@ static void raid_presuspend(struct dm_target *ti)
                mddev->pers->prepare_suspend(mddev);
 }
 
+static void raid_presuspend_undo(struct dm_target *ti)
+{
+       struct raid_set *rs = ti->private;
+
+       clear_bit(RT_FLAG_RS_FROZEN, &rs->runtime_flags);
+}
+
 static void raid_postsuspend(struct dm_target *ti)
 {
        struct raid_set *rs = ti->private;
@@ -4085,6 +4101,7 @@ static void raid_resume(struct dm_target *ti)
 
                WARN_ON_ONCE(!test_bit(MD_RECOVERY_FROZEN, &mddev->recovery));
                WARN_ON_ONCE(test_bit(MD_RECOVERY_RUNNING, &mddev->recovery));
+               clear_bit(RT_FLAG_RS_FROZEN, &rs->runtime_flags);
                mddev_lock_nointr(mddev);
                mddev->ro = 0;
                mddev->in_sync = 0;
@@ -4105,6 +4122,7 @@ static struct target_type raid_target = {
        .iterate_devices = raid_iterate_devices,
        .io_hints = raid_io_hints,
        .presuspend = raid_presuspend,
+       .presuspend_undo = raid_presuspend_undo,
        .postsuspend = raid_postsuspend,
        .preresume = raid_preresume,
        .resume = raid_resume,

diff --git a/drivers/md/md.c b/drivers/md/md.c
index 167db7744239276727ae47170febae374b94367d..64d544f09295c57291effe10b7b68df88bbe7b5b 100644 (file)
--- a/drivers/md/md.c
+++ b/drivers/md/md.c
@@ -366,7 +366,7 @@ static bool is_suspended(struct mddev *mddev, struct bio *bio)
        return true;
 }
 
-void md_handle_request(struct mddev *mddev, struct bio *bio)
+bool md_handle_request(struct mddev *mddev, struct bio *bio)
 {
 check_suspended:
        if (is_suspended(mddev, bio)) {
@@ -374,7 +374,7 @@ check_suspended:
                /* Bail out if REQ_NOWAIT is set for the bio */
                if (bio->bi_opf & REQ_NOWAIT) {
                        bio_wouldblock_error(bio);
-                       return;
+                       return true;
                }
                for (;;) {
                        prepare_to_wait(&mddev->sb_wait, &__wait,
@@ -390,10 +390,13 @@ check_suspended:
 
        if (!mddev->pers->make_request(mddev, bio)) {
                percpu_ref_put(&mddev->active_io);
+               if (!mddev->gendisk && mddev->pers->prepare_suspend)
+                       return false;
                goto check_suspended;
        }
 
        percpu_ref_put(&mddev->active_io);
+       return true;
 }
 EXPORT_SYMBOL(md_handle_request);
 
@@ -8733,6 +8736,23 @@ void md_account_bio(struct mddev *mddev, struct bio **bio)
 }
 EXPORT_SYMBOL_GPL(md_account_bio);
 
+void md_free_cloned_bio(struct bio *bio)
+{
+       struct md_io_clone *md_io_clone = bio->bi_private;
+       struct bio *orig_bio = md_io_clone->orig_bio;
+       struct mddev *mddev = md_io_clone->mddev;
+
+       if (bio->bi_status && !orig_bio->bi_status)
+               orig_bio->bi_status = bio->bi_status;
+
+       if (md_io_clone->start_time)
+               bio_end_io_acct(orig_bio, md_io_clone->start_time);
+
+       bio_put(bio);
+       percpu_ref_put(&mddev->active_io);
+}
+EXPORT_SYMBOL_GPL(md_free_cloned_bio);
+
 /* md_allow_write(mddev)
  * Calling this ensures that the array is marked 'active' so that writes
  * may proceed without blocking.  It is important to call this before

diff --git a/drivers/md/md.h b/drivers/md/md.h
index 8041df038b5e9eab80757fdaf77aa126679aeb5d..556db28a49aaeb02c5c61d3d72cb7257f7b6991c 100644 (file)
--- a/drivers/md/md.h
+++ b/drivers/md/md.h
@@ -793,6 +793,7 @@ extern void md_finish_reshape(struct mddev *mddev);
 void md_submit_discard_bio(struct mddev *mddev, struct md_rdev *rdev,
                        struct bio *bio, sector_t start, sector_t size);
 void md_account_bio(struct mddev *mddev, struct bio **bio);
+void md_free_cloned_bio(struct bio *bio);
 
 extern bool __must_check md_flush_request(struct mddev *mddev, struct bio *bio);
 extern void md_super_write(struct mddev *mddev, struct md_rdev *rdev,
@@ -821,7 +822,7 @@ extern void md_stop_writes(struct mddev *mddev);
 extern int md_rdev_init(struct md_rdev *rdev);
 extern void md_rdev_clear(struct md_rdev *rdev);
 
-extern void md_handle_request(struct mddev *mddev, struct bio *bio);
+extern bool md_handle_request(struct mddev *mddev, struct bio *bio);
 extern int mddev_suspend(struct mddev *mddev, bool interruptible);
 extern void mddev_resume(struct mddev *mddev);
 extern void md_idle_sync_thread(struct mddev *mddev);

diff --git a/drivers/md/raid5.c b/drivers/md/raid5.c
index 48129de21aecc22119f04f219de639c1d21e0cb2..388da55e274e2a0f47f66b4ab0fc6482397a011b 100644 (file)
--- a/drivers/md/raid5.c
+++ b/drivers/md/raid5.c
@@ -760,6 +760,7 @@ enum stripe_result {
        STRIPE_RETRY,
        STRIPE_SCHEDULE_AND_RETRY,
        STRIPE_FAIL,
+       STRIPE_WAIT_RESHAPE,
 };
 
 struct stripe_request_ctx {
@@ -5937,7 +5938,8 @@ static enum stripe_result make_stripe_request(struct mddev *mddev,
                        if (ahead_of_reshape(mddev, logical_sector,
                                             conf->reshape_safe)) {
                                spin_unlock_irq(&conf->device_lock);
-                               return STRIPE_SCHEDULE_AND_RETRY;
+                               ret = STRIPE_SCHEDULE_AND_RETRY;
+                               goto out;
                        }
                }
                spin_unlock_irq(&conf->device_lock);
@@ -6016,6 +6018,12 @@ static enum stripe_result make_stripe_request(struct mddev *mddev,
 
 out_release:
        raid5_release_stripe(sh);
+out:
+       if (ret == STRIPE_SCHEDULE_AND_RETRY && reshape_interrupted(mddev)) {
+               bi->bi_status = BLK_STS_RESOURCE;
+               ret = STRIPE_WAIT_RESHAPE;
+               pr_err_ratelimited("dm-raid456: io across reshape position while reshape can't make progress");
+       }
        return ret;
 }
 
@@ -6137,7 +6145,7 @@ static bool raid5_make_request(struct mddev *mddev, struct bio * bi)
        while (1) {
                res = make_stripe_request(mddev, conf, &ctx, logical_sector,
                                          bi);
-               if (res == STRIPE_FAIL)
+               if (res == STRIPE_FAIL || res == STRIPE_WAIT_RESHAPE)
                        break;
 
                if (res == STRIPE_RETRY)
@@ -6175,6 +6183,11 @@ static bool raid5_make_request(struct mddev *mddev, struct bio * bi)
 
        if (rw == WRITE)
                md_write_end(mddev);
+       if (res == STRIPE_WAIT_RESHAPE) {
+               md_free_cloned_bio(bi);
+               return false;
+       }
+
        bio_endio(bi);
        return true;
 }
@@ -8925,6 +8938,18 @@ static int raid5_start(struct mddev *mddev)
        return r5l_start(conf->log);
 }
 
+/*
+ * This is only used for dm-raid456, caller already frozen sync_thread, hence
+ * if rehsape is still in progress, io that is waiting for reshape can never be
+ * done now, hence wake up and handle those IO.
+ */
+static void raid5_prepare_suspend(struct mddev *mddev)
+{
+       struct r5conf *conf = mddev->private;
+
+       wake_up(&conf->wait_for_overlap);
+}
+
 static struct md_personality raid6_personality =
 {
        .name           = "raid6",
@@ -8948,6 +8973,7 @@ static struct md_personality raid6_personality =
        .quiesce        = raid5_quiesce,
        .takeover       = raid6_takeover,
        .change_consistency_policy = raid5_change_consistency_policy,
+       .prepare_suspend = raid5_prepare_suspend,
 };
 static struct md_personality raid5_personality =
 {
@@ -8972,6 +8998,7 @@ static struct md_personality raid5_personality =
        .quiesce        = raid5_quiesce,
        .takeover       = raid5_takeover,
        .change_consistency_policy = raid5_change_consistency_policy,
+       .prepare_suspend = raid5_prepare_suspend,
 };
 
 static struct md_personality raid4_personality =
@@ -8997,6 +9024,7 @@ static struct md_personality raid4_personality =
        .quiesce        = raid5_quiesce,
        .takeover       = raid4_takeover,
        .change_consistency_policy = raid5_change_consistency_policy,
+       .prepare_suspend = raid5_prepare_suspend,
 };
 
 static int __init raid5_init(void)