1 files changed, 21 insertions, 2 deletions

diff --git a/fs/fs-writeback.c b/fs/fs-writeback.c
index 81e086d8aa57..5581122bd2c0 100644
--- a/fs/fs-writeback.c
+++ b/fs/fs-writeback.c
@@ -52,8 +52,6 @@ struct wb_writeback_work {
 #define CREATE_TRACE_POINTS
 #include <trace/events/writeback.h>
 
-#define inode_to_bdi(inode)     ((inode)->i_mapping->backing_dev_info)
-
 /*
  * We don't actually have pdflush, but this one is exported though /proc...
  */
@@ -71,6 +69,27 @@ int writeback_in_progress(struct backing_dev_info *bdi)
         return test_bit(BDI_writeback_running, &bdi->state);
 }
 
+static inline struct backing_dev_info *inode_to_bdi(struct inode *inode)
+{
+        struct super_block *sb = inode->i_sb;
+        struct backing_dev_info *bdi = inode->i_mapping->backing_dev_info;
+
+        /*
+         * For inodes on standard filesystems, we use superblock's bdi. For
+         * inodes on virtual filesystems, we want to use inode mapping's bdi
+         * because they can possibly point to something useful (think about
+         * block_dev filesystem).
+         */
+        if (sb->s_bdi && sb->s_bdi != &noop_backing_dev_info) {
+                /* Some device inodes could play dirty tricks. Catch them... */
+                WARN(bdi != sb->s_bdi && bdi_cap_writeback_dirty(bdi),
+                        "Dirtiable inode bdi %s != sb bdi %s\n",
+                        bdi->name, sb->s_bdi->name);
+                return sb->s_bdi;
+        }
+        return bdi;
+}
+
 static void bdi_queue_work(struct backing_dev_info *bdi,
                 struct wb_writeback_work *work)
 {