Catch filesystems lacking s_bdi

noop_backing_dev_info is used only as a flag to mark filesystems that
don't have any backing store, like tmpfs, procfs, spufs, etc.

Signed-off-by: Joern Engel <joern@logfs.org>

Changed the BUG_ON() to a WARN_ON(). Note that adding dirty inodes
to the noop_backing_dev_info is not legal and will not result in
them being flushed, but we already catch this condition in
__mark_inode_dirty() when checking for a registered bdi.

Signed-off-by: Jens Axboe <jens.axboe@oracle.com>

1 files changed, 2 insertions, 1 deletions

diff --git a/fs/sync.c b/fs/sync.c
index fc5c3d75cf3c..92b228176f7c 100644
--- a/fs/sync.c
+++ b/fs/sync.c
@@ -14,6 +14,7 @@
 #include <linux/pagemap.h>
 #include <linux/quotaops.h>
 #include <linux/buffer_head.h>
+#include <linux/backing-dev.h>
 #include "internal.h"
 
 #define VALID_FLAGS (SYNC_FILE_RANGE_WAIT_BEFORE|SYNC_FILE_RANGE_WRITE| \
@@ -32,7 +33,7 @@ static int __sync_filesystem(struct super_block *sb, int wait)
          * This should be safe, as we require bdi backing to actually
          * write out data in the first place
          */
-        if (!sb->s_bdi)
+        if (!sb->s_bdi || sb->s_bdi == &noop_backing_dev_info)
                 return 0;
 
         if (sb->s_qcop && sb->s_qcop->quota_sync)