ceph: fix deadlock or deadcode of misusing dget()

[ Upstream commit b493ad718b1f0357394d2cdecbf00a44a36fa085 ]

The lock order is incorrect between denty and its parent, we should
always make sure that the parent get the lock first.

But since this deadcode is never used and the parent dir will always
be set from the callers, let's just remove it.

Link: https://lore.kernel.org/r/20231116081919.GZ1957730@ZenIV
Reported-by: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: Xiubo Li <xiubli@redhat.com>
Reviewed-by: Jeff Layton <jlayton@kernel.org>
Signed-off-by: Ilya Dryomov <idryomov@gmail.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>

diff --git a/fs/ceph/caps.c b/fs/ceph/caps.c
index 14215ec..7f7e5f5 100644 (file)
--- a/fs/ceph/caps.c
+++ b/fs/ceph/caps.c
@@ -4780,12 +4780,14 @@ int ceph_encode_dentry_release(void **p, struct dentry *dentry,
                               struct inode *dir,
                               int mds, int drop, int unless)
 {
-       struct dentry *parent = NULL;
        struct ceph_mds_request_release *rel = *p;
        struct ceph_dentry_info *di = ceph_dentry(dentry);
        int force = 0;
        int ret;
 
+       /* This shouldn't happen */
+       BUG_ON(!dir);
+
        /*
         * force an record for the directory caps if we have a dentry lease.
         * this is racy (can't take i_ceph_lock and d_lock together), but it
@@ -4795,14 +4797,9 @@ int ceph_encode_dentry_release(void **p, struct dentry *dentry,
        spin_lock(&dentry->d_lock);
        if (di->lease_session && di->lease_session->s_mds == mds)
                force = 1;
-       if (!dir) {
-               parent = dget(dentry->d_parent);
-               dir = d_inode(parent);
-       }
        spin_unlock(&dentry->d_lock);
 
        ret = ceph_encode_inode_release(p, dir, mds, drop, unless, force);
-       dput(parent);
 
        spin_lock(&dentry->d_lock);
        if (ret && di->lease_session && di->lease_session->s_mds == mds) {