1 files changed, 19 insertions, 22 deletions

diff --git a/drivers/md/dm-snap.c b/drivers/md/dm-snap.c
index 7401540086df..874f145431d8 100644
--- a/drivers/md/dm-snap.c
+++ b/drivers/md/dm-snap.c
@@ -49,6 +49,11 @@ struct pending_exception {
         struct bio_list snapshot_bios;
 
         /*
+         * Short-term queue of pending exceptions prior to submission.
+         */
+        struct list_head list;
+
+        /*
          * Other pending_exceptions that are processing this
          * chunk.  When this list is empty, we know we can
          * complete the origins.
@@ -930,8 +935,9 @@ static int __origin_write(struct list_head *snapshots, struct bio *bio)
         int r = 1, first = 1;
         struct dm_snapshot *snap;
         struct exception *e;
-        struct pending_exception *pe, *last = NULL;
+        struct pending_exception *pe, *next_pe, *last = NULL;
         chunk_t chunk;
+        LIST_HEAD(pe_queue);
 
         /* Do all the snapshots on this origin */
         list_for_each_entry (snap, snapshots, list) {
@@ -965,12 +971,19 @@ static int __origin_write(struct list_head *snapshots, struct bio *bio)
                                 snap->valid = 0;
 
                         } else {
-                                if (last)
+                                if (first) {
+                                        bio_list_add(&pe->origin_bios, bio);
+                                        r = 0;
+                                        first = 0;
+                                }
+                                if (last && list_empty(&pe->siblings))
                                         list_merge(&pe->siblings,
                                                    &last->siblings);
-
+                                if (!pe->started) {
+                                        pe->started = 1;
+                                        list_add_tail(&pe->list, &pe_queue);
+                                }
                                 last = pe;
-                                r = 0;
                         }
                 }
 
@@ -980,24 +993,8 @@ static int __origin_write(struct list_head *snapshots, struct bio *bio)
         /*
          * Now that we have a complete pe list we can start the copying.
          */
-        if (last) {
-                pe = last;
-                do {
-                        down_write(&pe->snap->lock);
-                        if (first)
-                                bio_list_add(&pe->origin_bios, bio);
-                        if (!pe->started) {
-                                pe->started = 1;
-                                up_write(&pe->snap->lock);
-                                start_copy(pe);
-                        } else
-                                up_write(&pe->snap->lock);
-                        first = 0;
-                        pe = list_entry(pe->siblings.next,
-                                        struct pending_exception, siblings);
-
-                } while (pe != last);
-        }
+        list_for_each_entry_safe(pe, next_pe, &pe_queue, list)
+                start_copy(pe);
 
         return r;
 }