scsi: sd: Move sd_read_cpr() out of the q->limits_lock region

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@wdc.com>
Link: https://lore.kernel.org/r/20240801054234.540532-1-shinichiro.kawasaki@wdc.com
Tested-by: Luca Coelho <luciano.coelho@intel.com>
Reviewed-by: Damien Le Moal <dlemoal@kernel.org>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Bart Van Assche <bvanassche@acm.org>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>

diff --git a/drivers/scsi/sd.c b/drivers/scsi/sd.c
index 8bb3a361185152f81d6a41f56462a84dfc64a99f..718eb91ba9a5918b314bfbf96b5848b4073263c2 100644 (file)
--- 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