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@xxxxxxxxxx>
Suggested-by: Mike Snitzer <snitzer@xxxxxxxxxx>
Signed-off-by: Martin K. Petersen <martin.petersen@xxxxxxxxxx>
---
I contemplated making blk_peek_request() use rq->errors to decide what
to return up the stack. However, I cringed at mixing errnos and SCSI
midlayer status information in the same location.
---
block/blk-core.c | 6 ++++--
drivers/scsi/sd.c | 4 ++--
include/linux/blkdev.h | 9 ++++++---
3 files changed, 12 insertions(+), 7 deletions(-)
diff --git a/block/blk-core.c b/block/blk-core.c
index 33e2f62d5062..ee833af2f892 100644
--- a/block/blk-core.c
+++ b/block/blk-core.c
@@ -2446,14 +2446,16 @@ 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 ec163d08f6c3..6e841c6da632 100644
--- 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 c70e3588a48c..e990d181625a 100644
--- a/include/linux/blkdev.h
+++ b/include/linux/blkdev.h
@@ -680,9 +680,12 @@ 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_INVALID, /* invalid command, kill, return -EREMOTEIO */
+ BLKPREP_DEFER, /* leave on queue */
+};
extern unsigned long blk_max_low_pfn, blk_max_pfn;
--
2.7.0
--
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