Commit bbd848e0 authored May 05, 2016 by Mike Snitzer Committed by Jens Axboe May 05, 2016

block: reinstate early return of -EOPNOTSUPP from blkdev_issue_discard

Commit 38f25255 ("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: 38f25255 ("block: add __blkdev_issue_discard")
Signed-off-by: Mike Snitzer <snitzer@redhat.com>
Signed-off-by: Jens Axboe <axboe@fb.com>

parent a21f2a3e

block/blk-lib.c

+5 −2

Original line number	Diff line number	Diff line
		@@ -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);

Admin message