From c66213921c816f6b1b16a84911618ba9a363b134 Mon Sep 17 00:00:00 2001 From: Mikulas Patocka Date: Thu, 2 Apr 2009 19:55:25 +0100 Subject: [PATCH] dm snapshot: avoid dropping lock in __find_pending_exception It is uncommon and bug-prone to drop a lock in a function that is called with the lock held, so this is moved to the caller. Cc: stable@kernel.org Signed-off-by: Mikulas Patocka Signed-off-by: Alasdair G Kergon --- drivers/md/dm-snap.c | 42 ++++++++++++++++++++++++------------------ 1 file changed, 24 insertions(+), 18 deletions(-) diff --git a/drivers/md/dm-snap.c b/drivers/md/dm-snap.c index 87a2803ba6bd..eb7291a84203 100644 --- a/drivers/md/dm-snap.c +++ b/drivers/md/dm-snap.c @@ -992,23 +992,10 @@ __lookup_pending_exception(struct dm_snapshot *s, chunk_t chunk) * this. */ static struct dm_snap_pending_exception * -__find_pending_exception(struct dm_snapshot *s, struct bio *bio) +__find_pending_exception(struct dm_snapshot *s, + struct dm_snap_pending_exception *pe, chunk_t chunk) { - struct dm_snap_pending_exception *pe, *pe2; - chunk_t chunk = sector_to_chunk(s, bio->bi_sector); - - /* - * Create a new pending exception, we don't want - * to hold the lock while we do this. - */ - up_write(&s->lock); - pe = alloc_pending_exception(s); - down_write(&s->lock); - - if (!s->valid) { - free_pending_exception(pe); - return NULL; - } + struct dm_snap_pending_exception *pe2; pe2 = __lookup_pending_exception(s, chunk); if (pe2) { @@ -1083,7 +1070,17 @@ static int snapshot_map(struct dm_target *ti, struct bio *bio, if (bio_rw(bio) == WRITE) { pe = __lookup_pending_exception(s, chunk); if (!pe) { - pe = __find_pending_exception(s, bio); + up_write(&s->lock); + pe = alloc_pending_exception(s); + down_write(&s->lock); + + if (!s->valid) { + free_pending_exception(pe); + r = -EIO; + goto out_unlock; + } + + pe = __find_pending_exception(s, pe, chunk); if (!pe) { __invalidate_snapshot(s, -ENOMEM); r = -EIO; @@ -1220,7 +1217,16 @@ static int __origin_write(struct list_head *snapshots, struct bio *bio) pe = __lookup_pending_exception(snap, chunk); if (!pe) { - pe = __find_pending_exception(snap, bio); + up_write(&snap->lock); + pe = alloc_pending_exception(snap); + down_write(&snap->lock); + + if (!snap->valid) { + free_pending_exception(pe); + goto next_snapshot; + } + + pe = __find_pending_exception(snap, pe, chunk); if (!pe) { __invalidate_snapshot(snap, -ENOMEM); goto next_snapshot; -- 2.20.1