block: cope with WRITE ZEROES failing in blkdev_issue_zeroout()

BugLink: https://bugs.launchpad.net/bugs/1726818
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: Hannes Reinecke <hare@suse.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Martin K. Petersen <martin.petersen@oracle.com>
Signed-off-by: Ilya Dryomov <idryomov@gmail.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Acked-by: Kleber Souza <kleber.souza@canonical.com>
Signed-off-by: Khalid Elmously <khalid.elmously@canonical.com>

diff --git a/block/blk-lib.c b/block/blk-lib.c
index 4ef942c27ad2bc5c135a69ae712a84c13e3c0a48..595517c514e563df6128c27c900c95a07da876b7 100644 (file)
--- a/block/blk-lib.c
+++ b/block/blk-lib.c
@@ -321,12 +321,6 @@ static int __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.
  *
@@ -370,18 +364,49 @@ EXPORT_SYMBOL(__blkdev_issue_zeroout);
 int blkdev_issue_zeroout(struct block_device *bdev, sector_t sector,
                sector_t nr_sects, gfp_t gfp_mask, unsigned flags)
 {
-       int ret;
-       struct bio *bio = NULL;
+       int ret = 0;
+       sector_t bs_mask;
+       struct bio *bio;
        struct blk_plug plug;
+       bool try_write_zeroes = !!bdev_write_zeroes_sectors(bdev);
 
+       bs_mask = (bdev_logical_block_size(bdev) >> 9) - 1;
+       if ((sector | nr_sects) & bs_mask)
+               return -EINVAL;
+
+retry:
+       bio = NULL;
        blk_start_plug(&plug);
-       ret = __blkdev_issue_zeroout(bdev, sector, nr_sects, gfp_mask,
-                       &bio, flags);
+       if (try_write_zeroes) {
+               ret = __blkdev_issue_write_zeroes(bdev, sector, nr_sects,
+                                                 gfp_mask, &bio, flags);
+       } else if (!(flags & BLKDEV_ZERO_NOFALLBACK)) {
+               ret = __blkdev_issue_zero_pages(bdev, sector, nr_sects,
+                                               gfp_mask, &bio);
+       } else {
+               /* No zeroing offload support */
+               ret = -EOPNOTSUPP;
+       }
        if (ret == 0 && bio) {
                ret = submit_bio_wait(bio);
                bio_put(bio);
        }
        blk_finish_plug(&plug);
+       if (ret && try_write_zeroes) {
+               if (!(flags & BLKDEV_ZERO_NOFALLBACK)) {
+                       try_write_zeroes = false;
+                       goto retry;
+               }
+               if (!bdev_write_zeroes_sectors(bdev)) {
+                       /*
+                        * Zeroing offload support was indicated, but the
+                        * device reported ILLEGAL REQUEST (for some devices
+                        * there is no non-destructive way to verify whether
+                        * WRITE ZEROES is actually supported).
+                        */
+                       ret = -EOPNOTSUPP;
+               }
+       }
 
        return ret;
 }