dm writecache: correct uncommitted_block when discarding uncommitted entry

commit 39495b1 upstream.

When uncommitted entry has been discarded, correct wc->uncommitted_block
for getting the exact number.

Fixes: 48debaf ("dm: add writecache target")
Cc: [email protected]
Signed-off-by: Huaisheng Ye <[email protected]>
Acked-by: Mikulas Patocka <[email protected]>
Signed-off-by: Mike Snitzer <[email protected]>
Signed-off-by: Greg Kroah-Hartman <[email protected]>

Author: LenovoOpenLab

drivers/md/dm-writecache.c

@@ -857,6 +857,8 @@ static void writecache_discard(struct dm_writecache *wc, sector_t start, sector_
 				writecache_wait_for_ios(wc, WRITE);
 				discarded_something = true;
 			}
+			if (!writecache_entry_is_committed(wc, e))
+				wc->uncommitted_blocks--;
 			writecache_free_entry(wc, e);
 		}