[PATCH] device-mapper: make lock_fs optional

Devices only needs syncing when creating snapshots, so make this optional when
suspending a device.

Signed-off-by: Alasdair G Kergon <agk@redhat.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

3 files changed, 16 insertions, 7 deletions

diff --git a/drivers/md/dm-ioctl.c b/drivers/md/dm-ioctl.c
index 3e327db57310..dbc07afd4462 100644
--- a/drivers/md/dm-ioctl.c
+++ b/drivers/md/dm-ioctl.c
@@ -700,7 +700,7 @@ static int do_suspend(struct dm_ioctl *param)
                 return -ENXIO;
 
         if (!dm_suspended(md))
-                r = dm_suspend(md);
+                r = dm_suspend(md, 1);
 
         if (!r)
                 r = __dev_status(md, param);
@@ -738,7 +738,7 @@ static int do_resume(struct dm_ioctl *param)
         if (new_map) {
                 /* Suspend if it isn't already suspended */
                 if (!dm_suspended(md))
-                        dm_suspend(md);
+                        dm_suspend(md, 1);
 
                 r = dm_swap_table(md, new_map);
                 if (r) {
diff --git a/drivers/md/dm.c b/drivers/md/dm.c
index fc335e09d072..0e481512f918 100644
--- a/drivers/md/dm.c
+++ b/drivers/md/dm.c
@@ -55,6 +55,7 @@ union map_info *dm_get_mapinfo(struct bio *bio)
  */
 #define DMF_BLOCK_IO 0
 #define DMF_SUSPENDED 1
+#define DMF_FROZEN 2
 
 struct mapped_device {
         struct rw_semaphore io_lock;
@@ -1021,6 +1022,8 @@ static int lock_fs(struct mapped_device *md)
                 return r;
         }
 
+        set_bit(DMF_FROZEN, &md->flags);
+
         /* don't bdput right now, we don't want the bdev
          * to go away while it is locked.
          */
@@ -1029,8 +1032,12 @@ static int lock_fs(struct mapped_device *md)
 
 static void unlock_fs(struct mapped_device *md)
 {
+        if (!test_bit(DMF_FROZEN, &md->flags))
+                return;
+
         thaw_bdev(md->suspended_bdev, md->frozen_sb);
         md->frozen_sb = NULL;
+        clear_bit(DMF_FROZEN, &md->flags);
 }
 
 /*
@@ -1040,7 +1047,7 @@ static void unlock_fs(struct mapped_device *md)
  * dm_bind_table, dm_suspend must be called to flush any in
  * flight bios and ensure that any further io gets deferred.
  */
-int dm_suspend(struct mapped_device *md)
+int dm_suspend(struct mapped_device *md, int do_lockfs)
 {
         struct dm_table *map = NULL;
         DECLARE_WAITQUEUE(wait, current);
@@ -1064,9 +1071,11 @@ int dm_suspend(struct mapped_device *md)
         }
 
         /* Flush I/O to the device. */
-        r = lock_fs(md);
-        if (r)
-                goto out;
+        if (do_lockfs) {
+                r = lock_fs(md);
+                if (r)
+                        goto out;
+        }
 
         /*
          * First we set the BLOCK_IO flag so no more ios will be mapped.
diff --git a/drivers/md/dm.h b/drivers/md/dm.h
index 95a0cfbe5b4d..4eaf075da217 100644
--- a/drivers/md/dm.h
+++ b/drivers/md/dm.h
@@ -69,7 +69,7 @@ void dm_put(struct mapped_device *md);
 /*
  * A device can still be used while suspended, but I/O is deferred.
  */
-int dm_suspend(struct mapped_device *md);
+int dm_suspend(struct mapped_device *md, int with_lockfs);
 int dm_resume(struct mapped_device *md);
 
 /*