block: reinstate early return of -EOPNOTSUPP from blkdev_issue_discard

Commit 38f25255330 ("block: add __blkdev_issue_discard") incorrectly
disallowed the early return of -EOPNOTSUPP if the device doesn't support
discard (or secure discard).  This early return of -EOPNOTSUPP has
always been part of blkdev_issue_discard() interface so there isn't a
good reason to break that behaviour -- especially when it can be easily
reinstated.

The nuance of allowing early return of -EOPNOTSUPP vs disallowing late
return of -EOPNOTSUPP is: if the overall device never advertised support
for discards and one is issued to the device it is beneficial to inform
the caller that discards are not supported via -EOPNOTSUPP.  But if a
device advertises discard support it means that at least a subset of the
device does have discard support -- but it could be that discards issued
to some regions of a stacked device will not be supported.  In that case
the late return of -EOPNOTSUPP must be disallowed.

Fixes: 38f25255330 ("block: add __blkdev_issue_discard")
Signed-off-by: Mike Snitzer <snitzer@redhat.com>
Signed-off-by: Jens Axboe <axboe@fb.com>

diff --git a/block/blk-lib.c b/block/blk-lib.c
index ccbce2b2ea053a7d22f9e06c4ad6587a2ccafdc6..23d7f301a1967483ec79a383a1a317881caf3358 100644 (file)
--- a/block/blk-lib.c
+++ b/block/blk-lib.c
@@ -109,11 +109,14 @@ int blkdev_issue_discard(struct block_device *bdev, sector_t sector,
        blk_start_plug(&plug);
        ret = __blkdev_issue_discard(bdev, sector, nr_sects, gfp_mask, type,
                        &bio);
-       if (!ret && bio)
+       if (!ret && bio) {
                ret = submit_bio_wait(type, bio);
+               if (ret == -EOPNOTSUPP)
+                       ret = 0;
+       }
        blk_finish_plug(&plug);
 
-       return ret != -EOPNOTSUPP ? ret : 0;
+       return ret;
 }
 EXPORT_SYMBOL(blkdev_issue_discard);