[PATCH md-6.8 v2 8/9] dm-raid456, md/raid456: fix a deadlock for dm-raid456 while io concurrent with reshape
From: Yu Kuai
Date: Tue Mar 05 2024 - 02:31:24 EST
From: Yu Kuai <yukuai3@xxxxxxxxxx>
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.
Signed-off-by: Yu Kuai <yukuai3@xxxxxxxxxx>
Signed-off-by: Xiao Ni <xni@xxxxxxxxxx>
Acked-by: Mike Snitzer <snitzer@xxxxxxxxxx>
---
drivers/md/dm-raid.c | 22 ++++++++++++++++++++--
drivers/md/md.c | 24 ++++++++++++++++++++++--
drivers/md/md.h | 3 ++-
drivers/md/raid5.c | 32 ++++++++++++++++++++++++++++++--
4 files changed, 74 insertions(+), 7 deletions(-)
diff --git a/drivers/md/dm-raid.c b/drivers/md/dm-raid.c
index 7d48943acd57..ea45f777691c 100644
--- 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 e9e666240e9f..50d7bfa3c6f9 100644
--- 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 @@ void md_handle_request(struct mddev *mddev, struct bio *bio)
/* 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 @@ void md_handle_request(struct mddev *mddev, struct bio *bio)
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);
@@ -8758,6 +8761,23 @@ 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 2db0a75febf9..3133650b57d4 100644
--- a/drivers/md/md.h
+++ b/drivers/md/md.h
@@ -782,6 +782,7 @@ 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,
@@ -810,7 +811,7 @@ 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 6a7a32f7fb91..38a49f6eb54b 100644
--- 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 {
@@ -5946,7 +5947,8 @@ 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);
@@ -6025,6 +6027,12 @@ 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;
}
@@ -6146,7 +6154,7 @@ 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)
@@ -6184,6 +6192,11 @@ 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;
}
@@ -8909,6 +8922,18 @@ 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",
@@ -8932,6 +8957,7 @@ 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 =
{
@@ -8956,6 +8982,7 @@ 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 =
@@ -8981,6 +9008,7 @@ 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)
--
2.39.2