fuse: nlookup missing decrement in fuse_direntplus_link

During our debugging of glusterfs, we found an Assertion failed error:
inode_lookup >= nlookup, which was caused by the nlookup value in the
kernel being greater than that in the FUSE file system.

The issue was introduced by fuse_direntplus_link, where in the function,
fuse_iget increments nlookup, and if d_splice_alias returns failure,
fuse_direntplus_link returns failure without decrementing nlookup
https://github.com/gluster/glusterfs/pull/4081

Signed-off-by: ruanmeisi <ruan.meisi@zte.com.cn>
Fixes: 0b05b18381ee ("fuse: implement NFS-like readdirplus support")
Cc: <stable@vger.kernel.org> # v3.9
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>

diff --git a/fs/fuse/readdir.c b/fs/fuse/readdir.c
index dc60347..b3d4981 100644 (file)
--- a/fs/fuse/readdir.c
+++ b/fs/fuse/readdir.c
@@ -243,8 +243,16 @@ retry:
                        dput(dentry);
                        dentry = alias;
                }
-               if (IS_ERR(dentry))
+               if (IS_ERR(dentry)) {
+                       if (!IS_ERR(inode)) {
+                               struct fuse_inode *fi = get_fuse_inode(inode);
+
+                               spin_lock(&fi->lock);
+                               fi->nlookup--;
+                               spin_unlock(&fi->lock);
+                       }
                        return PTR_ERR(dentry);
+               }
        }
        if (fc->readdirplus_auto)
                set_bit(FUSE_I_INIT_RDPLUS, &get_fuse_inode(inode)->state);