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authorMikulas Patocka <mpatocka@redhat.com>2016-01-08 19:07:55 -0500
committerMike Snitzer <snitzer@redhat.com>2016-01-08 20:03:05 -0500
commit385277bfb57faac44e92497104ba542cdd82d5fe (patch)
treea705a7644d3bb515779335252473b0f53810c854 /drivers/md/dm-snap-persistent.c
parent1c2e54e1ed6f0a87ae628c520768a53dc60bc2f4 (diff)
dm snapshot: fix hung bios when copy error occurs
When there is an error copying a chunk dm-snapshot can incorrectly hold associated bios indefinitely, resulting in hung IO. The function copy_callback sets pe->error if there was error copying the chunk, and then calls complete_exception. complete_exception calls pending_complete on error, otherwise it calls commit_exception with commit_callback (and commit_callback calls complete_exception). The persistent exception store (dm-snap-persistent.c) assumes that calls to prepare_exception and commit_exception are paired. persistent_prepare_exception increases ps->pending_count and persistent_commit_exception decreases it. If there is a copy error, persistent_prepare_exception is called but persistent_commit_exception is not. This results in the variable ps->pending_count never returning to zero and that causes some pending exceptions (and their associated bios) to be held forever. Fix this by unconditionally calling commit_exception regardless of whether the copy was successful. A new "valid" parameter is added to commit_exception -- when the copy fails this parameter is set to zero so that the chunk that failed to copy (and all following chunks) is not recorded in the snapshot store. Also, remove commit_callback now that it is merely a wrapper around pending_complete. Signed-off-by: Mikulas Patocka <mpatocka@redhat.com> Signed-off-by: Mike Snitzer <snitzer@redhat.com> Cc: stable@vger.kernel.org
Diffstat (limited to 'drivers/md/dm-snap-persistent.c')
-rw-r--r--drivers/md/dm-snap-persistent.c5
1 files changed, 4 insertions, 1 deletions
diff --git a/drivers/md/dm-snap-persistent.c b/drivers/md/dm-snap-persistent.c
index 3164b8bce294..4d3909393f2c 100644
--- a/drivers/md/dm-snap-persistent.c
+++ b/drivers/md/dm-snap-persistent.c
@@ -695,7 +695,7 @@ static int persistent_prepare_exception(struct dm_exception_store *store,
}
static void persistent_commit_exception(struct dm_exception_store *store,
- struct dm_exception *e,
+ struct dm_exception *e, int valid,
void (*callback) (void *, int success),
void *callback_context)
{
@@ -704,6 +704,9 @@ static void persistent_commit_exception(struct dm_exception_store *store,
struct core_exception ce;
struct commit_callback *cb;
+ if (!valid)
+ ps->valid = 0;
+
ce.old_chunk = e->old_chunk;
ce.new_chunk = e->new_chunk;
write_exception(ps, ps->current_committed++, &ce);