dm: split dm_suspend io_lock hold into two

Change io_locking to allow processing flush in separate thread.

Because we have DMF_BLOCK_IO already set, any possible
new ios are queued in dm_requests now.

In the case of interrupting previous wait there can be more
ios queued (we unlocked io_lock for a while) but this is safe.

Signed-off-by: Milan Broz <mbroz@redhat.com>
Signed-off-by: Alasdair G Kergon <agk@redhat.com>

1 files changed, 2 insertions, 1 deletions

diff --git a/drivers/md/dm.c b/drivers/md/dm.c
index 5191954a18b2..11f422ecfda0 100644
--- a/drivers/md/dm.c
+++ b/drivers/md/dm.c
@@ -1434,9 +1434,11 @@ int dm_suspend(struct mapped_device *md, unsigned suspend_flags)
 
         if (noflush)
                 __merge_pushback_list(md);
+        up_write(&md->io_lock);
 
         /* were we interrupted ? */
         if (pending) {
+                down_write(&md->io_lock);
                 __flush_deferred_io(md);
                 up_write(&md->io_lock);
 
@@ -1444,7 +1446,6 @@ int dm_suspend(struct mapped_device *md, unsigned suspend_flags)
                 r = -EINTR;
                 goto out; /* pushback list is already flushed, so skip flush */
         }
-        up_write(&md->io_lock);
 
         dm_table_postsuspend_targets(map);