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authorMikulas Patocka <mpatocka@redhat.com>2008-10-30 13:33:12 +0000
committerAlasdair G Kergon <agk@redhat.com>2008-10-30 13:33:12 +0000
commit60c856c8e2f57a3f69c505735ef66e3719ea0bd6 (patch)
treea6295bec9c1fa01885ef14befa4ae3618f51ca57 /drivers/md
parentb34578a48459ed1bd5396631aaa4a65d6bcc7726 (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>
Diffstat (limited to 'drivers/md')
-rw-r--r--drivers/md/dm-snap.c16
1 files changed, 9 insertions, 7 deletions
diff --git a/drivers/md/dm-snap.c b/drivers/md/dm-snap.c
index b2d9d1ac28ad..746603b42f86 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);