dm snapshot: refactor __find_pending_exception

Move looking-up of a pending exception from __find_pending_exception to another
function.

Cc: stable@kernel.org
Signed-off-by: Mikulas Patocka <mpatocka@redhat.com>
Signed-off-by: Alasdair G Kergon <agk@redhat.com>

1 files changed, 28 insertions, 24 deletions

diff --git a/drivers/md/dm-snap.c b/drivers/md/dm-snap.c
index 65ff82ff124e..87a2803ba6bd 100644
--- a/drivers/md/dm-snap.c
+++ b/drivers/md/dm-snap.c
@@ -972,6 +972,17 @@ static void start_copy(struct dm_snap_pending_exception *pe)
                     &src, 1, &dest, 0, copy_callback, pe);
 }
 
+static struct dm_snap_pending_exception *
+__lookup_pending_exception(struct dm_snapshot *s, chunk_t chunk)
+{
+        struct dm_snap_exception *e = lookup_exception(&s->pending, chunk);
+
+        if (!e)
+                return NULL;
+
+        return container_of(e, struct dm_snap_pending_exception, e);
+}
+
 /*
  * Looks to see if this snapshot already has a pending exception
  * for this chunk, otherwise it allocates a new one and inserts
@@ -983,21 +994,10 @@ static void start_copy(struct dm_snap_pending_exception *pe)
 static struct dm_snap_pending_exception *
 __find_pending_exception(struct dm_snapshot *s, struct bio *bio)
 {
-        struct dm_snap_exception *e;
-        struct dm_snap_pending_exception *pe;
+        struct dm_snap_pending_exception *pe, *pe2;
         chunk_t chunk = sector_to_chunk(s, bio->bi_sector);
 
         /*
-         * Is there a pending exception for this already ?
-         */
-        e = lookup_exception(&s->pending, chunk);
-        if (e) {
-                /* cast the exception to a pending exception */
-                pe = container_of(e, struct dm_snap_pending_exception, e);
-                goto out;
-        }
-
-        /*
          * Create a new pending exception, we don't want
          * to hold the lock while we do this.
          */
@@ -1010,11 +1010,10 @@ __find_pending_exception(struct dm_snapshot *s, struct bio *bio)
                 return NULL;
         }
 
-        e = lookup_exception(&s->pending, chunk);
-        if (e) {
+        pe2 = __lookup_pending_exception(s, chunk);
+        if (pe2) {
                 free_pending_exception(pe);
-                pe = container_of(e, struct dm_snap_pending_exception, e);
-                goto out;
+                return pe2;
         }
 
         pe->e.old_chunk = chunk;
@@ -1032,7 +1031,6 @@ __find_pending_exception(struct dm_snapshot *s, struct bio *bio)
         get_pending_exception(pe);
         insert_exception(&s->pending, &pe->e);
 
- out:
         return pe;
 }
 
@@ -1083,11 +1081,14 @@ static int snapshot_map(struct dm_target *ti, struct bio *bio,
          * writeable.
          */
         if (bio_rw(bio) == WRITE) {
-                pe = __find_pending_exception(s, bio);
+                pe = __lookup_pending_exception(s, chunk);
                 if (!pe) {
-                        __invalidate_snapshot(s, -ENOMEM);
-                        r = -EIO;
-                        goto out_unlock;
+                        pe = __find_pending_exception(s, bio);
+                        if (!pe) {
+                                __invalidate_snapshot(s, -ENOMEM);
+                                r = -EIO;
+                                goto out_unlock;
+                        }
                 }
 
                 remap_exception(s, &pe->e, bio, chunk);
@@ -1217,10 +1218,13 @@ static int __origin_write(struct list_head *snapshots, struct bio *bio)
                 if (e)
                         goto next_snapshot;
 
-                pe = __find_pending_exception(snap, bio);
+                pe = __lookup_pending_exception(snap, chunk);
                 if (!pe) {
-                        __invalidate_snapshot(snap, -ENOMEM);
-                        goto next_snapshot;
+                        pe = __find_pending_exception(snap, bio);
+                        if (!pe) {
+                                __invalidate_snapshot(snap, -ENOMEM);
+                                goto next_snapshot;
+                        }
                 }
 
                 if (!primary_pe) {