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authorMikulas Patocka <mpatocka@redhat.com>2016-01-08 19:07:55 -0500
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>2016-03-03 15:06:23 -0800
commiteeb7b0e01658684a743ccfd66a668e8a56d5ebb9 (patch)
tree5cad39303bb234d7ae4d8cca04e8a3fde8a13d25
parent2cd529968dd0647bf75e24f4e36fef99fc536b58 (diff)
downloadlinux-linaro-stable-eeb7b0e01658684a743ccfd66a668e8a56d5ebb9.tar.gz
dm snapshot: fix hung bios when copy error occurs
commit 385277bfb57faac44e92497104ba542cdd82d5fe upstream. 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> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
-rw-r--r--drivers/md/dm-exception-store.h2
-rw-r--r--drivers/md/dm-snap-persistent.c5
-rw-r--r--drivers/md/dm-snap-transient.c4
-rw-r--r--drivers/md/dm-snap.c20
4 files changed, 12 insertions, 19 deletions
diff --git a/drivers/md/dm-exception-store.h b/drivers/md/dm-exception-store.h
index 0b2536247cf5..84e27708ad97 100644
--- a/drivers/md/dm-exception-store.h
+++ b/drivers/md/dm-exception-store.h
@@ -70,7 +70,7 @@ struct dm_exception_store_type {
* Update the metadata with this exception.
*/
void (*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);
diff --git a/drivers/md/dm-snap-persistent.c b/drivers/md/dm-snap-persistent.c
index 2d2b1b7588d7..8f6d3ea55401 100644
--- a/drivers/md/dm-snap-persistent.c
+++ b/drivers/md/dm-snap-persistent.c
@@ -646,7 +646,7 @@ 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)
{
@@ -655,6 +655,9 @@ 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);
diff --git a/drivers/md/dm-snap-transient.c b/drivers/md/dm-snap-transient.c
index 1ce9a2586e41..31439d53cf7e 100644
--- a/drivers/md/dm-snap-transient.c
+++ b/drivers/md/dm-snap-transient.c
@@ -52,12 +52,12 @@ static int transient_prepare_exception(struct dm_exception_store *store,
}
static void transient_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)
{
/* Just succeed */
- callback(callback_context, 1);
+ callback(callback_context, valid);
}
static void transient_usage(struct dm_exception_store *store,
diff --git a/drivers/md/dm-snap.c b/drivers/md/dm-snap.c
index d892a05c84f4..dbd0f00f7395 100644
--- a/drivers/md/dm-snap.c
+++ b/drivers/md/dm-snap.c
@@ -1388,8 +1388,9 @@ static void __invalidate_snapshot(struct dm_snapshot *s, int err)
dm_table_event(s->ti->table);
}
-static void pending_complete(struct dm_snap_pending_exception *pe, int success)
+static void pending_complete(void *context, int success)
{
+ struct dm_snap_pending_exception *pe = context;
struct dm_exception *e;
struct dm_snapshot *s = pe->snap;
struct bio *origin_bios = NULL;
@@ -1459,24 +1460,13 @@ out:
free_pending_exception(pe);
}
-static void commit_callback(void *context, int success)
-{
- struct dm_snap_pending_exception *pe = context;
-
- pending_complete(pe, success);
-}
-
static void complete_exception(struct dm_snap_pending_exception *pe)
{
struct dm_snapshot *s = pe->snap;
- if (unlikely(pe->copy_error))
- pending_complete(pe, 0);
-
- else
- /* Update the metadata if we are persistent */
- s->store->type->commit_exception(s->store, &pe->e,
- commit_callback, pe);
+ /* Update the metadata if we are persistent */
+ s->store->type->commit_exception(s->store, &pe->e, !pe->copy_error,
+ pending_complete, pe);
}
/*