The function blk_revalidate_disk_zones() calls the function
disk_update_zone_resources() after freezing the device queue. In turn,
disk_update_zone_resources() calls queue_limits_start_update() which
takes a queue limits mutex lock, resulting in the ordering:
q->q_usage_counter check -> q->limits_lock. However, the usual ordering
is to always take a queue limit lock before freezing the queue to commit
the limits updates, e.g., the code pattern:
lim = queue_limits_start_update(q);
...
blk_mq_freeze_queue(q);
ret = queue_limits_commit_update(q, &lim);
blk_mq_unfreeze_queue(q);
Thus, blk_revalidate_disk_zones() introduces a potential circular
locking dependency deadlock that lockdep sometimes catches with the
splat:
[ 51.934109] ======================================================
[ 51.935916] WARNING: possible circular locking dependency detected
[ 51.937561] 6.12.0+ #2107 Not tainted
[ 51.938648] ------------------------------------------------------
[ 51.940351] kworker/u16:4/157 is trying to acquire lock:
[ 51.941805] ffff9fff0aa0bea8 (&q->limits_lock){+.+.}-{4:4}, at: disk_update_zone_resources+0x86/0x170
[ 51.944314]
but task is already holding lock:
[ 51.945688] ffff9fff0aa0b890 (&q->q_usage_counter(queue)#3){++++}-{0:0}, at: blk_revalidate_disk_zones+0x15f/0x340
[ 51.948527]
which lock already depends on the new lock.
[ 51.951296]
the existing dependency chain (in reverse order) is:
[ 51.953708]
-> #1 (&q->q_usage_counter(queue)#3){++++}-{0:0}:
[ 51.956131] blk_queue_enter+0x1c9/0x1e0
[ 51.957290] blk_mq_alloc_request+0x187/0x2a0
[ 51.958365] scsi_execute_cmd+0x78/0x490 [scsi_mod]
[ 51.959514] read_capacity_16+0x111/0x410 [sd_mod]
[ 51.960693] sd_revalidate_disk.isra.0+0x872/0x3240 [sd_mod]
[ 51.962004] sd_probe+0x2d7/0x520 [sd_mod]
[ 51.962993] really_probe+0xd5/0x330
[ 51.963898] __driver_probe_device+0x78/0x110
[ 51.964925] driver_probe_device+0x1f/0xa0
[ 51.965916] __driver_attach_async_helper+0x60/0xe0
[ 51.967017] async_run_entry_fn+0x2e/0x140
[ 51.968004] process_one_work+0x21f/0x5a0
[ 51.968987] worker_thread+0x1dc/0x3c0
[ 51.969868] kthread+0xe0/0x110
[ 51.970377] ret_from_fork+0x31/0x50
[ 51.970983] ret_from_fork_asm+0x11/0x20
[ 51.971587]
-> #0 (&q->limits_lock){+.+.}-{4:4}:
[ 51.972479] __lock_acquire+0x1337/0x2130
[ 51.973133] lock_acquire+0xc5/0x2d0
[ 51.973691] __mutex_lock+0xda/0xcf0
[ 51.974300] disk_update_zone_resources+0x86/0x170
[ 51.975032] blk_revalidate_disk_zones+0x16c/0x340
[ 51.975740] sd_zbc_revalidate_zones+0x73/0x160 [sd_mod]
[ 51.976524] sd_revalidate_disk.isra.0+0x465/0x3240 [sd_mod]
[ 51.977824] sd_probe+0x2d7/0x520 [sd_mod]
[ 51.978917] really_probe+0xd5/0x330
[ 51.979915] __driver_probe_device+0x78/0x110
[ 51.981047] driver_probe_device+0x1f/0xa0
[ 51.982143] __driver_attach_async_helper+0x60/0xe0
[ 51.983282] async_run_entry_fn+0x2e/0x140
[ 51.984319] process_one_work+0x21f/0x5a0
[ 51.985873] worker_thread+0x1dc/0x3c0
[ 51.987289] kthread+0xe0/0x110
[ 51.988546] ret_from_fork+0x31/0x50
[ 51.989926] ret_from_fork_asm+0x11/0x20
[ 51.991376]
other info that might help us debug this:
[ 51.994127] Possible unsafe locking scenario:
[ 51.995651] CPU0 CPU1
[ 51.996694] ---- ----
[ 51.997716] lock(&q->q_usage_counter(queue)#3);
[ 51.998817] lock(&q->limits_lock);
[ 52.000043] lock(&q->q_usage_counter(queue)#3);
[ 52.001638] lock(&q->limits_lock);
[ 52.002485]
*** DEADLOCK ***
Prevent this issue by moving the calls to blk_mq_freeze_queue() and
blk_mq_unfreeze_queue() around the call to queue_limits_commit_update()
in disk_update_zone_resources(). disk_free_zone_resources() is also
modified to operate with the queue frozen as before by adding calls to
blk_mq_freeze_queue() and blk_mq_unfreeze_queue().
Fixes: 843283e96e5a ("block: Fake max open zones limit when there is no limit")
Cc: stable@xxxxxxxxxxxxxxx
Signed-off-by: Damien Le Moal <dlemoal@xxxxxxxxxx>
---
block/blk-zoned.c | 15 ++++++++++++---
1 file changed, 12 insertions(+), 3 deletions(-)
diff --git a/block/blk-zoned.c b/block/blk-zoned.c
index 70211751df16..1f961088b813 100644
--- a/block/blk-zoned.c
+++ b/block/blk-zoned.c
@@ -1468,9 +1468,13 @@ static unsigned int disk_set_conv_zones_bitmap(struct gendisk *disk,
void disk_free_zone_resources(struct gendisk *disk)
{
+ struct request_queue *q = disk->queue;
+
if (!disk->zone_wplugs_pool)
return;
+ blk_mq_freeze_queue(q);
+
cancel_work_sync(&disk->zone_wplugs_work);
if (disk->zone_wplugs_wq) {
@@ -1493,6 +1497,8 @@ void disk_free_zone_resources(struct gendisk *disk)
disk->zone_capacity = 0;
disk->last_zone_capacity = 0;
disk->nr_zones = 0;
+
+ blk_mq_unfreeze_queue(q);
}
static inline bool disk_need_zone_resources(struct gendisk *disk)
@@ -1551,6 +1557,7 @@ static int disk_update_zone_resources(struct gendisk *disk,
unsigned int nr_seq_zones, nr_conv_zones;
unsigned int pool_size;
struct queue_limits lim;
+ int ret;
disk->nr_zones = args->nr_zones;
disk->zone_capacity = args->zone_capacity;
@@ -1601,7 +1608,11 @@ static int disk_update_zone_resources(struct gendisk *disk,
}
commit:
- return queue_limits_commit_update(q, &lim);
+ blk_mq_freeze_queue(q);
+ ret = queue_limits_commit_update(q, &lim);
+ blk_mq_unfreeze_queue(q);
+
+ return ret;
}
static int blk_revalidate_conv_zone(struct blk_zone *zone, unsigned int idx,
@@ -1816,14 +1827,12 @@ int blk_revalidate_disk_zones(struct gendisk *disk)
* Set the new disk zone parameters only once the queue is frozen and
* all I/Os are completed.
*/
- blk_mq_freeze_queue(q);
if (ret > 0)
ret = disk_update_zone_resources(disk, &args);
else
pr_warn("%s: failed to revalidate zones\n", disk->disk_name);
if (ret)
disk_free_zone_resources(disk);
- blk_mq_unfreeze_queue(q);
return ret;
}
--
2.47.0
