FAILED: patch "[PATCH] fuse: nlookup missing decrement in fuse_direntplus_link" failed to apply to 4.19-stable tree

[<gregkh@linuxfoundation.org>]

The patch below does not apply to the 4.19-stable tree.
If someone wants it applied there, or to any other stable or longterm
tree, then please email the backport, including the original git commit
id to <stable@vger.kernel.org>.

To reproduce the conflict and resubmit, you may use the following commands:

git fetch https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/ linux-4.19.y
git checkout FETCH_HEAD
git cherry-pick -x b8bd342d50cbf606666488488f9fea374aceb2d5
# <resolve conflicts, build, test, etc.>
git commit -s
git send-email --to '<stable@vger.kernel.org>' --in-reply-to '2023091601-spotted-untie-0ba4@gregkh' --subject-prefix 'PATCH 4.19.y' HEAD^..

Possible dependencies:

b8bd342d50cb ("fuse: nlookup missing decrement in fuse_direntplus_link")
d123d8e1833c ("fuse: split out readdir.c")

thanks,

greg k-h

------------------ original commit in Linus's tree ------------------

From b8bd342d50cbf606666488488f9fea374aceb2d5 Mon Sep 17 00:00:00 2001
From: ruanmeisi <ruan.meisi@zte.com.cn>
Date: Tue, 25 Apr 2023 19:13:54 +0800
Subject: [PATCH] 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 dc603479b30e..b3d498163f97 100644
--- a/fs/fuse/readdir.c
+++ b/fs/fuse/readdir.c
@@ -243,8 +243,16 @@ static int fuse_direntplus_link(struct file *file,
 			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);