scsi: scsi_debug: Fix qc_lock use in sdebug_blk_mq_poll()

The use of the 'locked' boolean variable to control locking and unlocking
of the qc_lock spinlock of struct sdebug_queue confuses sparse, leading to
a warning about an unexpected unlock. Simplify the qc_lock lock/unlock
handling code of this function to avoid this warning by removing the
'locked' boolean variable. This change also fixes unlocked access to the
in_use_bm bitmap with the find_first_bit() function.

Link: https://lore.kernel.org/r/20220301113009.595857-3-damien.lemoal@opensource.wdc.com
Fixes: 1d05c32dafb5 ("scsi: scsi_debug: Refine sdebug_blk_mq_poll()")
Cc: stable@vger.kernel.org
Signed-off-by: Damien Le Moal <damien.lemoal@opensource.wdc.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>

diff --git a/drivers/scsi/scsi_debug.c b/drivers/scsi/scsi_debug.c
index f4e97f2224b224fc3f1ff757c6ef32c7ae86e571..25fa8e93f5a8b7a20ba57386ca8f9829e103d3a5 100644 (file)
--- a/drivers/scsi/scsi_debug.c
+++ b/drivers/scsi/scsi_debug.c
@@ -7509,7 +7509,6 @@ static int sdebug_blk_mq_poll(struct Scsi_Host *shost, unsigned int queue_num)
 {
        bool first;
        bool retiring = false;
-       bool locked = false;
        int num_entries = 0;
        unsigned int qc_idx = 0;
        unsigned long iflags;
@@ -7525,11 +7524,9 @@ static int sdebug_blk_mq_poll(struct Scsi_Host *shost, unsigned int queue_num)
        if (qc_idx >= sdebug_max_queue)
                return 0;
 
+       spin_lock_irqsave(&sqp->qc_lock, iflags);
+
        for (first = true; first || qc_idx + 1 < sdebug_max_queue; )   {
-               if (!locked) {
-                       spin_lock_irqsave(&sqp->qc_lock, iflags);
-                       locked = true;
-               }
                if (first) {
                        first = false;
                        if (!test_bit(qc_idx, sqp->in_use_bm))
@@ -7586,14 +7583,15 @@ static int sdebug_blk_mq_poll(struct Scsi_Host *shost, unsigned int queue_num)
                }
                WRITE_ONCE(sd_dp->defer_t, SDEB_DEFER_NONE);
                spin_unlock_irqrestore(&sqp->qc_lock, iflags);
-               locked = false;
                scsi_done(scp); /* callback to mid level */
                num_entries++;
+               spin_lock_irqsave(&sqp->qc_lock, iflags);
                if (find_first_bit(sqp->in_use_bm, sdebug_max_queue) >= sdebug_max_queue)
-                       break;  /* if no more then exit without retaking spinlock */
+                       break;
        }
-       if (locked)
-               spin_unlock_irqrestore(&sqp->qc_lock, iflags);
+
+       spin_unlock_irqrestore(&sqp->qc_lock, iflags);
+
        if (num_entries > 0)
                atomic_add(num_entries, &sdeb_mq_poll_count);
        return num_entries;