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authorMikulas Patocka <mpatocka@redhat.com>2009-04-02 19:55:25 +0100
committerAlasdair G Kergon <agk@redhat.com>2009-04-02 19:55:25 +0100
commitc66213921c816f6b1b16a84911618ba9a363b134 (patch)
tree2b99c1ef34eea840fe3d517d8a20fb59a5a84044 /drivers/md
parent2913808eb56a6445a7b277eb8d17651c8defb035 (diff)
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 <mpatocka@redhat.com> Signed-off-by: Alasdair G Kergon <agk@redhat.com>
Diffstat (limited to 'drivers/md')
-rw-r--r--drivers/md/dm-snap.c42
1 files changed, 24 insertions, 18 deletions
diff --git a/drivers/md/dm-snap.c b/drivers/md/dm-snap.c
index 87a2803ba6b..eb7291a8420 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;