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Commit 6d3d1a9c authored by Kent Overstreet's avatar Kent Overstreet
Browse files

bcache: bugfix for race between moving_gc and bucket_invalidate 



There is a possibility for a bucket to be invalidated by the allocator
while moving_gc was copying it's contents to another bucket, if the
bucket only held cached data. To prevent this moving checks for
a stale ptr (to an invalidated bucket), before and after reads.
It it finds one, it simply ignores moving that data. This only
affects bcache if the moving_gc was turned on, note that it's
off by default.

Signed-off-by: default avatarNicholas Swenson <nks@daterainc.com>
Signed-off-by: default avatarKent Overstreet <kmo@daterainc.com>
parent bf0a628a

drivers/md/bcache/movinggc.c

+10 −0
Original line number Diff line number Diff line
@@ -64,11 +64,16 @@ static void write_moving_finish(struct closure *cl) 


static void read_moving_endio(struct bio *bio, int error)

{

	struct bbio *b = container_of(bio, struct bbio, bio);

	struct moving_io *io = container_of(bio->bi_private,

					    struct moving_io, cl);



	if (error)

		io->op.error = error;

	else if (!KEY_DIRTY(&b->key) &&

		 ptr_stale(io->op.c, &b->key, 0)) {

		io->op.error = -EINTR;

	}



	bch_bbio_endio(io->op.c, bio, error, "reading data to move");

}
@@ -140,6 +145,11 @@ static void read_moving(struct cache_set *c) 
		if (!w)

			break;



		if (ptr_stale(c, &w->key, 0)) {

			bch_keybuf_del(&c->moving_gc_keys, w);

			continue;

		}



		io = kzalloc(sizeof(struct moving_io) + sizeof(struct bio_vec)

			     * DIV_ROUND_UP(KEY_SIZE(&w->key), PAGE_SECTORS),

			     GFP_KERNEL);