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-rw-r--r--drivers/md/dm-snap.c28
1 files changed, 28 insertions, 0 deletions
diff --git a/drivers/md/dm-snap.c b/drivers/md/dm-snap.c
index de302702ab3..f4fd0cee9c3 100644
--- a/drivers/md/dm-snap.c
+++ b/drivers/md/dm-snap.c
@@ -134,6 +134,27 @@ static void stop_tracking_chunk(struct dm_snapshot *s,
mempool_free(c, s->tracked_chunk_pool);
}
+static int __chunk_is_tracked(struct dm_snapshot *s, chunk_t chunk)
+{
+ struct dm_snap_tracked_chunk *c;
+ struct hlist_node *hn;
+ int found = 0;
+
+ spin_lock_irq(&s->tracked_chunk_lock);
+
+ hlist_for_each_entry(c, hn,
+ &s->tracked_chunk_hash[DM_TRACKED_CHUNK_HASH(chunk)], node) {
+ if (c->chunk == chunk) {
+ found = 1;
+ break;
+ }
+ }
+
+ spin_unlock_irq(&s->tracked_chunk_lock);
+
+ return found;
+}
+
/*
* One of these per registered origin, held in the snapshot_origins hash
*/
@@ -840,6 +861,13 @@ static void pending_complete(struct dm_snap_pending_exception *pe, int success)
}
/*
+ * Check for conflicting reads. This is extremely improbable,
+ * so yield() is sufficient and there is no need for a wait queue.
+ */
+ while (__chunk_is_tracked(s, pe->e.old_chunk))
+ yield();
+
+ /*
* Add a proper exception, and remove the
* in-flight exception from the list.
*/