blkdev_issue_zeroout try discard/writesame first, if they fail, zeroout fallback to regular write. The problem is discard/writesame doesn't return error for -EOPNOTSUPP, then zeroout can't do fallback and leave disk data not changed. zeroout should have guaranteed zero-fill behavior.
BTW, I saw several callers of blkdev_issue_discard can handle -EOPNOTSUPP, not sure why blkdev_issue_discard not returns -EOPNOTSUPP. The same story for blkdev_issue_write_same. https://bugzilla.kernel.org/show_bug.cgi?id=118581 Cc: Sitsofe Wheeler <sits...@yahoo.com> Cc: Mike Snitzer <snit...@redhat.com> Cc: Jens Axboe <ax...@fb.com> Cc: Martin K. Petersen <martin.peter...@oracle.com> Signed-off-by: Shaohua Li <s...@fb.com> --- block/blk-lib.c | 35 ++++++++++++++++++++++++++--------- 1 file changed, 26 insertions(+), 9 deletions(-) diff --git a/block/blk-lib.c b/block/blk-lib.c index 23d7f30..232f9ea 100644 --- a/block/blk-lib.c +++ b/block/blk-lib.c @@ -95,8 +95,9 @@ EXPORT_SYMBOL(__blkdev_issue_discard); * Description: * Issue a discard request for the sectors in question. */ -int blkdev_issue_discard(struct block_device *bdev, sector_t sector, - sector_t nr_sects, gfp_t gfp_mask, unsigned long flags) +static int do_blkdev_issue_discard(struct block_device *bdev, sector_t sector, + sector_t nr_sects, gfp_t gfp_mask, unsigned long flags, + bool ignore_nosupport) { int type = REQ_WRITE | REQ_DISCARD; struct bio *bio = NULL; @@ -111,13 +112,20 @@ int blkdev_issue_discard(struct block_device *bdev, sector_t sector, &bio); if (!ret && bio) { ret = submit_bio_wait(type, bio); - if (ret == -EOPNOTSUPP) + if (ignore_nosupport && ret == -EOPNOTSUPP) ret = 0; } blk_finish_plug(&plug); return ret; } + +int blkdev_issue_discard(struct block_device *bdev, sector_t sector, + sector_t nr_sects, gfp_t gfp_mask, unsigned long flags) +{ + return do_blkdev_issue_discard(bdev, sector, nr_sects, gfp_mask, + flags, true); +} EXPORT_SYMBOL(blkdev_issue_discard); /** @@ -131,9 +139,9 @@ EXPORT_SYMBOL(blkdev_issue_discard); * Description: * Issue a write same request for the sectors in question. */ -int blkdev_issue_write_same(struct block_device *bdev, sector_t sector, +static int do_blkdev_issue_write_same(struct block_device *bdev, sector_t sector, sector_t nr_sects, gfp_t gfp_mask, - struct page *page) + struct page *page, bool ignore_nosupport) { struct request_queue *q = bdev_get_queue(bdev); unsigned int max_write_same_sectors; @@ -167,7 +175,15 @@ int blkdev_issue_write_same(struct block_device *bdev, sector_t sector, if (bio) ret = submit_bio_wait(REQ_WRITE | REQ_WRITE_SAME, bio); - return ret != -EOPNOTSUPP ? ret : 0; + return (ret != -EOPNOTSUPP || !ignore_nosupport) ? ret : 0; +} + +int blkdev_issue_write_same(struct block_device *bdev, sector_t sector, + sector_t nr_sects, gfp_t gfp_mask, + struct page *page) +{ + return do_blkdev_issue_write_same(bdev, sector, nr_sects, gfp_mask, + page, true); } EXPORT_SYMBOL(blkdev_issue_write_same); @@ -238,12 +254,13 @@ int blkdev_issue_zeroout(struct block_device *bdev, sector_t sector, struct request_queue *q = bdev_get_queue(bdev); if (discard && blk_queue_discard(q) && q->limits.discard_zeroes_data && - blkdev_issue_discard(bdev, sector, nr_sects, gfp_mask, 0) == 0) + do_blkdev_issue_discard(bdev, sector, nr_sects, gfp_mask, 0, + false) == 0) return 0; if (bdev_write_same(bdev) && - blkdev_issue_write_same(bdev, sector, nr_sects, gfp_mask, - ZERO_PAGE(0)) == 0) + do_blkdev_issue_write_same(bdev, sector, nr_sects, gfp_mask, + ZERO_PAGE(0), false) == 0) return 0; return __blkdev_issue_zeroout(bdev, sector, nr_sects, gfp_mask); -- 2.8.0.rc2
