From: Shin'ichiro Kawasaki <shinichiro.kawasaki@xxxxxxx>
Commit 804e498e0496 ("sd: convert to the atomic queue limits API")
introduced pairs of function calls to queue_limits_start_update() and
queue_limits_commit_update(). These two functions lock and unlock
q->limits_lock. In sd_revalidate_disk(), sd_read_cpr() is called after
queue_limits_start_update() call and before
queue_limits_commit_update() call. sd_read_cpr() locks q->sysfs_dir_lock
and &q->sysfs_lock. Then new lock dependencies were created between
q->limits_lock, q->sysfs_dir_lock and q->sysfs_lock, as follows:
sd_revalidate_disk
queue_limits_start_update
mutex_lock(&q->limits_lock)
sd_read_cpr
disk_set_independent_access_ranges
mutex_lock(&q->sysfs_dir_lock)
mutex_lock(&q->sysfs_lock)
mutex_unlock(&q->sysfs_lock)
mutex_unlock(&q->sysfs_dir_lock)
queue_limits_commit_update
mutex_unlock(&q->limits_lock)
However, the three locks already had reversed dependencies in other
places. Then the new dependencies triggered the lockdep WARN "possible
circular locking dependency detected" [1]. This WARN was observed by
running the blktests test case srp/002.
To avoid the WARN, move the sd_read_cpr() call in sd_revalidate_disk()
after the queue_limits_commit_update() call. In other words, move the
sd_read_cpr() call out of the q->limits_lock region.
[1] https://lore.kernel.org/linux-scsi/vlmv53ni3ltwxplig5qnw4xsl2h6ccxijfbqzekx76vxoim5a5@dekv7q3es3tx/
Fixes: 804e498e0496 ("sd: convert to the atomic queue limits API")
Signed-off-by: Shin'ichiro Kawasaki <shinichiro.kawasaki@xxxxxxx>
Signed-off-by: Luca Coelho <luciano.coelho@xxxxxxxxx>
---
drivers/scsi/sd.c | 9 ++++++++-
1 file changed, 8 insertions(+), 1 deletion(-)
diff --git a/drivers/scsi/sd.c b/drivers/scsi/sd.c
index adeaa8ab9951..08cbe3815006 100644
--- a/drivers/scsi/sd.c
+++ b/drivers/scsi/sd.c
@@ -3753,7 +3753,6 @@ static int sd_revalidate_disk(struct gendisk *disk)
sd_read_block_limits_ext(sdkp);
sd_read_block_characteristics(sdkp, &lim);
sd_zbc_read_zones(sdkp, &lim, buffer);
- sd_read_cpr(sdkp);
}
sd_print_capacity(sdkp, old_capacity);
@@ -3808,6 +3807,14 @@ static int sd_revalidate_disk(struct gendisk *disk)
if (err)
return err;
+ /*
+ * Query concurrent positioning ranges after
+ * queue_limits_commit_update() unlocked q->limits_lock to avoid
+ * deadlock with q->sysfs_dir_lock and q->sysfs_lock.
+ */
+ if (sdkp->media_present && scsi_device_supports_vpd(sdp))
+ sd_read_cpr(sdkp);
+
/*
* For a zoned drive, revalidating the zones can be done only once
* the gendisk capacity is set. So if this fails, set back the gendisk
--
2.39.2
