diff options
| author | Mikulas Patocka <mpatocka@redhat.com> | 2008-10-30 13:33:12 +0000 |
|---|---|---|
| committer | Alasdair G Kergon <agk@redhat.com> | 2008-10-30 13:33:12 +0000 |
| commit | 60c856c8e2f57a3f69c505735ef66e3719ea0bd6 (patch) | |
| tree | a6295bec9c1fa01885ef14befa4ae3618f51ca57 | |
| parent | b34578a48459ed1bd5396631aaa4a65d6bcc7726 (diff) | |
dm snapshot: fix register_snapshot deadlock
register_snapshot() performs a GFP_KERNEL allocation while holding
_origins_lock for write, but that could write out dirty pages onto a
device that attempts to acquire _origins_lock for read, resulting in
deadlock.
So move the allocation up before taking the lock.
This path is not performance-critical, so it doesn't matter that we
allocate memory and free it if we find that we won't need it.
Signed-off-by: Mikulas Patocka <mpatocka@redhat.com>
Signed-off-by: Alasdair G Kergon <agk@redhat.com>
| -rw-r--r-- | drivers/md/dm-snap.c | 16 |
1 files changed, 9 insertions, 7 deletions
diff --git a/drivers/md/dm-snap.c b/drivers/md/dm-snap.c index b2d9d1ac28a..746603b42f8 100644 --- a/drivers/md/dm-snap.c +++ b/drivers/md/dm-snap.c @@ -229,19 +229,21 @@ static void __insert_origin(struct origin *o) */ static int register_snapshot(struct dm_snapshot *snap) { - struct origin *o; + struct origin *o, *new_o; struct block_device *bdev = snap->origin->bdev; + new_o = kmalloc(sizeof(*new_o), GFP_KERNEL); + if (!new_o) + return -ENOMEM; + down_write(&_origins_lock); o = __lookup_origin(bdev); - if (!o) { + if (o) + kfree(new_o); + else { /* New origin */ - o = kmalloc(sizeof(*o), GFP_KERNEL); - if (!o) { - up_write(&_origins_lock); - return -ENOMEM; - } + o = new_o; /* Initialise the struct */ INIT_LIST_HEAD(&o->snapshots); |