Commit c0f04d88 authored Sep 23, 2013 by Kent Overstreet Committed by Linus Torvalds Sep 24, 2013

bcache: Fix flushes in writeback mode



In writeback mode, when we get a cache flush we need to make sure we
issue a flush to the backing device.

The code for sending down an extra flush was wrong - by cloning the bio
we were probably getting flags that didn't make sense for a bare flush,
and also the old code was firing for FUA bios, for which we don't need
to send a flush to the backing device.

This was causing data corruption somehow - the mechanism was never
determined, but this patch fixes it for the users that were seeing it.

Signed-off-by: Kent Overstreet <kmo@daterainc.com>
Cc: linux-stable <stable@vger.kernel.org> # >= v3.10
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

parent 84786438

drivers/md/bcache/request.c

+9 −6

Original line number	Diff line number	Diff line
		@@ -997,14 +997,17 @@ static void request_write(struct cached_dev dc, struct search s)
		} else {
		bch_writeback_add(dc);

		if (s->op.flush_journal) {
		if (bio->bi_rw & REQ_FLUSH) {
		/* Also need to send a flush to the backing device */
		s->op.cache_bio = bio_clone_bioset(bio, GFP_NOIO,
		struct bio *flush = bio_alloc_bioset(0, GFP_NOIO,
		dc->disk.bio_split);

		bio->bi_size = 0;
		bio->bi_vcnt = 0;
		closure_bio_submit(bio, cl, s->d);
		flush->bi_rw = WRITE_FLUSH;
		flush->bi_bdev = bio->bi_bdev;
		flush->bi_end_io = request_endio;
		flush->bi_private = cl;

		closure_bio_submit(flush, cl, s->d);
		} else {
		s->op.cache_bio = bio;
		}