fs: Assign bdi in super_block

We do this automatically in get_sb_bdev() from the set_bdev_super()
callback. Filesystems that have their own private backing_dev_info
must assign that in ->fill_super().

Note that ->s_bdi assignment is required for proper writeback!

Acked-by: Christoph Hellwig <hch@infradead.org>
Signed-off-by: Jens Axboe <jens.axboe@oracle.com>

1 files changed, 8 insertions, 1 deletions

diff --git a/fs/sync.c b/fs/sync.c
index 192340930bb4..c08467a5d7cb 100644
--- a/fs/sync.c
+++ b/fs/sync.c
@@ -27,6 +27,13 @@
  */
 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)
+                return 0;
+
         /* Avoid doing twice syncing and cache pruning for quota sync */
         if (!wait) {
                 writeout_quota_sb(sb, -1);
@@ -101,7 +108,7 @@ restart:
                 spin_unlock(&sb_lock);
 
                 down_read(&sb->s_umount);
-                if (!(sb->s_flags & MS_RDONLY) && sb->s_root)
+                if (!(sb->s_flags & MS_RDONLY) && sb->s_root && sb->s_bdi)
                         __sync_filesystem(sb, wait);
                 up_read(&sb->s_umount);