sd_config_write_same() ignores ->max_ws_blocks == 0 and resets it to
permit trying WRITE SAME on older SCSI devices, unless ->no_write_same
is set. Because REQ_OP_WRITE_ZEROES is implemented in terms of WRITE
SAME, blkdev_issue_zeroout() may fail with -EREMOTEIO:
$ fallocate -zn -l 1k /dev/sdg
fallocate: fallocate failed: Remote I/O error
$ fallocate -zn -l 1k /dev/sdg # OK
$ fallocate -zn -l 1k /dev/sdg # OK
The following calls succeed because sd_done() sets ->no_write_same in
response to a sense that would become BLK_STS_TARGET/-EREMOTEIO, causing
__blkdev_issue_zeroout() to fall back to generating ZERO_PAGE bios.
This means blkdev_issue_zeroout() must cope with WRITE ZEROES failing
and fall back to manually zeroing, unless BLKDEV_ZERO_NOFALLBACK is
specified. For BLKDEV_ZERO_NOFALLBACK case, return -EOPNOTSUPP if
sd_done() has just set ->no_write_same thus indicating lack of offload
support.
Fixes: c20cfc27a473 ("block: stop using blkdev_issue_write_same for zeroing")
Cc: Christoph Hellwig <hch@xxxxxx>
Cc: "Martin K. Petersen" <martin.petersen@xxxxxxxxxx>
Cc: Hannes Reinecke <hare@xxxxxxxx>
Signed-off-by: Ilya Dryomov <idryomov@xxxxxxxxx>
---
block/blk-lib.c | 27 +++++++++++++++++++++------
1 file changed, 21 insertions(+), 6 deletions(-)
diff --git a/block/blk-lib.c b/block/blk-lib.c
index 6b97feb71065..1cb402beb983 100644
--- a/block/blk-lib.c
+++ b/block/blk-lib.c
@@ -316,12 +316,6 @@ static void __blkdev_issue_zero_pages(struct block_device *bdev,
* Zero-fill a block range, either using hardware offload or by explicitly
* writing zeroes to the device.
*
- * Note that this function may fail with -EOPNOTSUPP if the driver signals
- * zeroing offload support, but the device fails to process the command (for
- * some devices there is no non-destructive way to verify whether this
- * operation is actually supported). In this case the caller should call
- * retry the call to blkdev_issue_zeroout() and the fallback path will be used.
- *
* If a device is using logical block provisioning, the underlying space will
* not be released if %flags contains BLKDEV_ZERO_NOUNMAP.
*
@@ -374,6 +368,27 @@ int blkdev_issue_zeroout(struct block_device *bdev, sector_t sector,
&bio, flags);
if (ret == 0 && bio) {
ret = submit_bio_wait(bio);
+ /*
+ * Fall back to a manual zeroout on any error, if allowed.
+ *
+ * Particularly, WRITE ZEROES may fail with -EREMOTEIO if the
+ * driver signals zeroing offload support, but the device
+ * fails to process the command (for some devices there is no
+ * non-destructive way to verify whether this operation is
+ * actually supported).
+ */
+ if (ret && bio_op(bio) == REQ_OP_WRITE_ZEROES) {
+ if (flags & BLKDEV_ZERO_NOFALLBACK) {
+ if (!bdev_write_zeroes_sectors(bdev))
+ ret = -EOPNOTSUPP;
+ } else {
+ bio_put(bio);
+ bio = NULL;
+ __blkdev_issue_zero_pages(bdev, sector,
+ nr_sects, gfp_mask, &bio);
+ ret = submit_bio_wait(bio);
+ }
+ }
bio_put(bio);
}
blk_finish_plug(&plug);
--
2.4.3
