fuse: destroy bdi on umount

If a fuse filesystem is unmounted but the device file descriptor
remains open and a new mount reuses the old device number, then the
mount fails with EEXIST and the following warning is printed in the
kernel log:

  WARNING: at fs/sysfs/dir.c:462 sysfs_add_one+0x35/0x3d()
  sysfs: duplicate filename '0:15' can not be created

The cause is that the bdi belonging to the fuse filesystem was
destoryed only after the device file was released.  Fix this by
calling bdi_destroy() from fuse_put_super() instead.

Signed-off-by: Miklos Szeredi <mszeredi@suse.cz>
CC: stable@kernel.org

2 files changed, 3 insertions, 2 deletions

diff --git a/fs/fuse/dev.c b/fs/fuse/dev.c
index e0c7ada08a1f..c4a3d9bbdaa8 100644
--- a/fs/fuse/dev.c
+++ b/fs/fuse/dev.c
@@ -281,7 +281,8 @@ __releases(&fc->lock)
                         fc->blocked = 0;
                         wake_up_all(&fc->blocked_waitq);
                 }
-                if (fc->num_background == FUSE_CONGESTION_THRESHOLD) {
+                if (fc->num_background == FUSE_CONGESTION_THRESHOLD &&
+                    fc->connected) {
                         clear_bdi_congested(&fc->bdi, READ);
                         clear_bdi_congested(&fc->bdi, WRITE);
                 }
diff --git a/fs/fuse/inode.c b/fs/fuse/inode.c
index dc649f6bc3e5..459b73dd45e1 100644
--- a/fs/fuse/inode.c
+++ b/fs/fuse/inode.c
@@ -292,6 +292,7 @@ static void fuse_put_super(struct super_block *sb)
         list_del(&fc->entry);
         fuse_ctl_remove_conn(fc);
         mutex_unlock(&fuse_mutex);
+        bdi_destroy(&fc->bdi);
         fuse_conn_put(fc);
 }
 
@@ -532,7 +533,6 @@ void fuse_conn_put(struct fuse_conn *fc)
                 if (fc->destroy_req)
                         fuse_request_free(fc->destroy_req);
                 mutex_destroy(&fc->inst_mutex);
-                bdi_destroy(&fc->bdi);
                 fc->release(fc);
         }
 }