[PATCH] device-mapper: fix deadlocks in core (prep)

Some code tidy-ups in preparation for the next patches.  Change
dm_table_pre/postsuspend_targets to accept NULL.  Use dm_suspended()
throughout.

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>

2 files changed, 39 insertions, 28 deletions

diff --git a/drivers/md/dm-table.c b/drivers/md/dm-table.c
index a5a4c0ed8a14..a6d3baa46f61 100644
--- a/drivers/md/dm-table.c
+++ b/drivers/md/dm-table.c
@@ -869,11 +869,17 @@ static void suspend_targets(struct dm_table *t, unsigned postsuspend)
 
 void dm_table_presuspend_targets(struct dm_table *t)
 {
+        if (!t)
+                return;
+
         return suspend_targets(t, 0);
 }
 
 void dm_table_postsuspend_targets(struct dm_table *t)
 {
+        if (!t)
+                return;
+
         return suspend_targets(t, 1);
 }
 
diff --git a/drivers/md/dm.c b/drivers/md/dm.c
index 54fabbf06678..f0cd8ea327d3 100644
--- a/drivers/md/dm.c
+++ b/drivers/md/dm.c
@@ -610,7 +610,7 @@ static int dm_flush_all(request_queue_t *q, struct gendisk *disk,
         int ret = -ENXIO;
 
         if (map) {
-                ret = dm_table_flush_all(md->map);
+                ret = dm_table_flush_all(map);
                 dm_table_put(map);
         }
 
@@ -854,7 +854,7 @@ static int __bind(struct mapped_device *md, struct dm_table *t)
         write_unlock(&md->map_lock);
 
         dm_table_get(t);
-        dm_table_event_callback(md->map, event_callback, md);
+        dm_table_event_callback(t, event_callback, md);
         dm_table_set_restrictions(t, q);
         return 0;
 }
@@ -935,7 +935,7 @@ void dm_put(struct mapped_device *md)
         struct dm_table *map = dm_get_table(md);
 
         if (atomic_dec_and_test(&md->holders)) {
-                if (!test_bit(DMF_SUSPENDED, &md->flags) && map) {
+                if (!dm_suspended(md)) {
                         dm_table_presuspend_targets(map);
                         dm_table_postsuspend_targets(map);
                 }
@@ -971,7 +971,7 @@ int dm_swap_table(struct mapped_device *md, struct dm_table *table)
         down_write(&md->lock);
 
         /* device must be suspended */
-        if (!test_bit(DMF_SUSPENDED, &md->flags))
+        if (!dm_suspended(md))
                 goto out;
 
         __unbind(md);
@@ -988,7 +988,7 @@ out:
  */
 static int __lock_fs(struct mapped_device *md)
 {
-        int error = -ENOMEM;
+        int r = -ENOMEM;
 
         if (test_and_set_bit(DMF_FS_LOCKED, &md->flags))
                 return 0;
@@ -1003,7 +1003,7 @@ static int __lock_fs(struct mapped_device *md)
 
         md->frozen_sb = freeze_bdev(md->frozen_bdev);
         if (IS_ERR(md->frozen_sb)) {
-                error = PTR_ERR(md->frozen_sb);
+                r = PTR_ERR(md->frozen_sb);
                 goto out_bdput;
         }
 
@@ -1019,7 +1019,7 @@ out_bdput:
         md->frozen_bdev = NULL;
 out:
         clear_bit(DMF_FS_LOCKED, &md->flags);
-        return error;
+        return r;
 }
 
 static void __unlock_fs(struct mapped_device *md)
@@ -1045,20 +1045,20 @@ int dm_suspend(struct mapped_device *md)
 {
         struct dm_table *map;
         DECLARE_WAITQUEUE(wait, current);
-        int error = -EINVAL;
+        int r = -EINVAL;
 
-        /* Flush I/O to the device. */
         down_read(&md->lock);
         if (test_bit(DMF_BLOCK_IO, &md->flags))
                 goto out_read_unlock;
 
         map = dm_get_table(md);
-        if (map)
-                /* This does not get reverted if there's an error later. */
-                dm_table_presuspend_targets(map);
 
-        error = __lock_fs(md);
-        if (error) {
+        /* This does not get reverted if there's an error later. */
+        dm_table_presuspend_targets(map);
+
+        /* Flush I/O to the device. */
+        r = __lock_fs(md);
+        if (r) {
                 dm_table_put(map);
                 goto out_read_unlock;
         }
@@ -1071,7 +1071,7 @@ int dm_suspend(struct mapped_device *md)
          * If the flag is already set we know another thread is trying to
          * suspend as well, so we leave the fs locked for this thread.
          */
-        error = -EINVAL;
+        r = -EINVAL;
         down_write(&md->lock);
         if (test_and_set_bit(DMF_BLOCK_IO, &md->flags)) {
                 if (map)
@@ -1106,15 +1106,14 @@ int dm_suspend(struct mapped_device *md)
         remove_wait_queue(&md->wait, &wait);
 
         /* were we interrupted ? */
-        error = -EINTR;
+        r = -EINTR;
         if (atomic_read(&md->pending))
                 goto out_unfreeze;
 
         set_bit(DMF_SUSPENDED, &md->flags);
 
         map = dm_get_table(md);
-        if (map)
-                dm_table_postsuspend_targets(map);
+        dm_table_postsuspend_targets(map);
         dm_table_put(map);
         up_write(&md->lock);
 
@@ -1125,25 +1124,29 @@ out_unfreeze:
         clear_bit(DMF_BLOCK_IO, &md->flags);
 out_write_unlock:
         up_write(&md->lock);
-        return error;
+        return r;
 
 out_read_unlock:
         up_read(&md->lock);
-        return error;
+        return r;
 }
 
 int dm_resume(struct mapped_device *md)
 {
+        int r = -EINVAL;
         struct bio *def;
-        struct dm_table *map = dm_get_table(md);
+        struct dm_table *map = NULL;
 
         down_write(&md->lock);
-        if (!map ||
-            !test_bit(DMF_SUSPENDED, &md->flags) ||
-            !dm_table_get_size(map)) {
+        if (!dm_suspended(md)) {
                 up_write(&md->lock);
-                dm_table_put(map);
-                return -EINVAL;
+                goto out;
+        }
+
+        map = dm_get_table(md);
+        if (!map || !dm_table_get_size(map)) {
+                up_write(&md->lock);
+                goto out;
         }
 
         dm_table_resume_targets(map);
@@ -1155,9 +1158,11 @@ int dm_resume(struct mapped_device *md)
         up_write(&md->lock);
         __unlock_fs(md);
         dm_table_unplug_all(map);
-        dm_table_put(map);
 
-        return 0;
+        r = 0;
+out:
+        dm_table_put(map);
+        return r;
 }
 
 /*-----------------------------------------------------------------