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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>
This commit is contained in:
Kent Overstreet 2013-09-23 23:17:36 -07:00 committed by Linus Torvalds
parent 84786438ed
commit c0f04d88e4
1 changed files with 9 additions and 6 deletions
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15
drivers/md/bcache/request.c
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@ -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,
dc->disk.bio_split);
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;
}