[PATCH 2/2] sd_zbc: Write unlock zones from sd_uninit_cmnd()

[Damien Le Moal]

Releasing the write lock of a zone when the write commnand that
acquired the lock completes can cause deadlocks with scsi-mq due to
potential queue reordering if the lock owning request is requeued and
not executed.

Since sd_uninit_cmnd() is always called when a request is requeued,
call sd_zbc_write_unlock_zone() from that function for write requests
that acquired a zone lock. Acquisition of a zone lock by a write command
is indicated using the new command flag SCMD_ZONE_WRITE_LOCK.

Signed-off-by: Damien Le Moal <damien.lem...@wdc.com>
---
 drivers/scsi/sd.c        | 3 +++
 drivers/scsi/sd_zbc.c    | 9 +++++----
 include/scsi/scsi_cmnd.h | 1 +
 3 files changed, 9 insertions(+), 4 deletions(-)

diff --git a/drivers/scsi/sd.c b/drivers/scsi/sd.c
index bea36adeee17..e2647f2d4430 100644
--- a/drivers/scsi/sd.c
+++ b/drivers/scsi/sd.c
@@ -1277,6 +1277,9 @@ static void sd_uninit_command(struct scsi_cmnd *SCpnt)
 {
        struct request *rq = SCpnt->request;
 
+       if (SCpnt->flags & SCMD_ZONE_WRITE_LOCK)
+               sd_zbc_write_unlock_zone(SCpnt);
+
        if (rq->rq_flags & RQF_SPECIAL_PAYLOAD)
                __free_page(rq->special_vec.bv_page);
 
diff --git a/drivers/scsi/sd_zbc.c b/drivers/scsi/sd_zbc.c
index 96855df9f49d..6423ae70477e 100644
--- a/drivers/scsi/sd_zbc.c
+++ b/drivers/scsi/sd_zbc.c
@@ -294,6 +294,9 @@ int sd_zbc_write_lock_zone(struct scsi_cmnd *cmd)
            test_and_set_bit(zno, sdkp->zones_wlock))
                return BLKPREP_DEFER;
 
+       WARN_ON(cmd->flags & SCMD_ZONE_WRITE_LOCK);
+       cmd->flags |= SCMD_ZONE_WRITE_LOCK;
+
        return BLKPREP_OK;
 }
 
@@ -302,9 +305,10 @@ void sd_zbc_write_unlock_zone(struct scsi_cmnd *cmd)
        struct request *rq = cmd->request;
        struct scsi_disk *sdkp = scsi_disk(rq->rq_disk);
 
-       if (sdkp->zones_wlock) {
+       if (sdkp->zones_wlock && cmd->flags & SCMD_ZONE_WRITE_LOCK) {
                unsigned int zno = sd_zbc_zone_no(sdkp, blk_rq_pos(rq));
                WARN_ON_ONCE(!test_bit(zno, sdkp->zones_wlock));
+               cmd->flags &= ~SCMD_ZONE_WRITE_LOCK;
                clear_bit_unlock(zno, sdkp->zones_wlock);
                smp_mb__after_atomic();
        }
@@ -335,9 +339,6 @@ void sd_zbc_complete(struct scsi_cmnd *cmd,
        case REQ_OP_WRITE_ZEROES:
        case REQ_OP_WRITE_SAME:
 
-               /* Unlock the zone */
-               sd_zbc_write_unlock_zone(cmd);
-
                if (result &&
                    sshdr->sense_key == ILLEGAL_REQUEST &&
                    sshdr->asc == 0x21)
diff --git a/include/scsi/scsi_cmnd.h b/include/scsi/scsi_cmnd.h
index a1266d318c85..6af198d8120b 100644
--- a/include/scsi/scsi_cmnd.h
+++ b/include/scsi/scsi_cmnd.h
@@ -57,6 +57,7 @@ struct scsi_pointer {
 /* for scmd->flags */
 #define SCMD_TAGGED            (1 << 0)
 #define SCMD_UNCHECKED_ISA_DMA (1 << 1)
+#define SCMD_ZONE_WRITE_LOCK   (1 << 2)
 
 struct scsi_cmnd {
        struct scsi_request req;
-- 
2.13.3