dm snapshot: fix metadata writing when suspending

When suspending a device-mapper device, dm_suspend() sleeps until all
necessary I/O is completed.  This state is triggered by a callback from
persistent_commit().  But some I/O can still be issued *after* the callback
(to prepare the next metadata area for use if the current one is full).  This
patch delays the callback until after that I/O is complete.

Signed-off-by: Mark McLoughlin <markmc@redhat.com>
Signed-off-by: Alasdair G Kergon <agk@redhat.com>
Signed-off-by: Adrian Bunk <bunk@stusta.de>

diff --git a/drivers/md/dm-exception-store.c b/drivers/md/dm-exception-store.c
index 34a75939a0cafb2ea1d3d22fc594fbfaf368e90f..ab8756a40e02a2add67eabaf7d4f2bbc57badea7 100644 (file)
--- a/drivers/md/dm-exception-store.c
+++ b/drivers/md/dm-exception-store.c
@@ -517,6 +517,16 @@ static void persistent_commit(struct exception_store *store,
                if (r)
                        ps->valid = 0;
 
+               /*
+                * Have we completely filled the current area ?
+                */
+               if (ps->current_committed == ps->exceptions_per_area) {
+                       ps->current_committed = 0;
+                       r = zero_area(ps, ps->current_area + 1);
+                       if (r)
+                               ps->valid = 0;
+               }
+
                for (i = 0; i < ps->callback_count; i++) {
                        cb = ps->callbacks + i;
                        cb->callback(cb->context, r == 0 ? 1 : 0);
@@ -524,16 +534,6 @@ static void persistent_commit(struct exception_store *store,
 
                ps->callback_count = 0;
        }
-
-       /*
-        * Have we completely filled the current area ?
-        */
-       if (ps->current_committed == ps->exceptions_per_area) {
-               ps->current_committed = 0;
-               r = zero_area(ps, ps->current_area + 1);
-               if (r)
-                       ps->valid = 0;
-       }
 }
 
 static void persistent_drop(struct exception_store *store)