block/sd: Return -EREMOTEIO when WRITE SAME and DISCARD are disabled

When a storage device rejects a WRITE SAME command we will disable write
same functionality for the device and return -EREMOTEIO to the block
layer. -EREMOTEIO will in turn prevent DM from retrying the I/O and/or
failing the path.

Yiwen Jiang discovered a small race where WRITE SAME requests issued
simultaneously would cause -EIO to be returned. This happened because
any requests being prepared after WRITE SAME had been disabled for the
device caused us to return BLKPREP_KILL. The latter caused the block
layer to return -EIO upon completion.

To overcome this we introduce BLKPREP_INVALID which indicates that this
is an invalid request for the device. blk_peek_request() is modified to
return -EREMOTEIO in that case.

Reported-by: Yiwen Jiang <jiangyiwen@huawei.com>
Suggested-by: Mike Snitzer <snitzer@redhat.com>
Reviewed-by: Hannes Reinicke <hare@suse.de>
Reviewed-by: Ewan Milne <emilne@redhat.com>
Reviewed-by: Yiwen Jiang <jiangyiwen@huawei.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>

diff --git a/block/blk-core.c b/block/blk-core.c
index 476244d..35607dd 100644 (file)
--- a/block/blk-core.c
+++ b/block/blk-core.c
@@ -2447,14 +2447,16 @@ struct request *blk_peek_request(struct request_queue *q)
 
                        rq = NULL;
                        break;
-               } else if (ret == BLKPREP_KILL) {
+               } else if (ret == BLKPREP_KILL || ret == BLKPREP_INVALID) {
+                       int err = (ret == BLKPREP_INVALID) ? -EREMOTEIO : -EIO;
+
                        rq->cmd_flags |= REQ_QUIET;
                        /*
                         * Mark this request as started so we don't trigger
                         * any debug logic in the end I/O path.
                         */
                        blk_start_request(rq);
-                       __blk_end_request_all(rq, -EIO);
+                       __blk_end_request_all(rq, err);
                } else {
                        printk(KERN_ERR "%s: bad return=%d\n", __func__, ret);
                        break;

diff --git a/drivers/scsi/sd.c b/drivers/scsi/sd.c
index ec163d0..6e841c6 100644 (file)
--- a/drivers/scsi/sd.c
+++ b/drivers/scsi/sd.c
@@ -761,7 +761,7 @@ static int sd_setup_discard_cmnd(struct scsi_cmnd *cmd)
                break;
 
        default:
-               ret = BLKPREP_KILL;
+               ret = BLKPREP_INVALID;
                goto out;
        }
 
@@ -839,7 +839,7 @@ static int sd_setup_write_same_cmnd(struct scsi_cmnd *cmd)
        int ret;
 
        if (sdkp->device->no_write_same)
-               return BLKPREP_KILL;
+               return BLKPREP_INVALID;
 
        BUG_ON(bio_offset(bio) || bio_iovec(bio).bv_len != sdp->sector_size);
 

diff --git a/include/linux/blkdev.h b/include/linux/blkdev.h
index d372ea8..a9b643a 100644 (file)
--- a/include/linux/blkdev.h
+++ b/include/linux/blkdev.h
@@ -681,9 +681,12 @@ static inline bool blk_write_same_mergeable(struct bio *a, struct bio *b)
 /*
  * q->prep_rq_fn return values
  */
-#define BLKPREP_OK             0       /* serve it */
-#define BLKPREP_KILL           1       /* fatal error, kill */
-#define BLKPREP_DEFER          2       /* leave on queue */
+enum {
+       BLKPREP_OK,             /* serve it */
+       BLKPREP_KILL,           /* fatal error, kill, return -EIO */
+       BLKPREP_DEFER,          /* leave on queue */
+       BLKPREP_INVALID,        /* invalid command, kill, return -EREMOTEIO */
+};
 
 extern unsigned long blk_max_low_pfn, blk_max_pfn;