FAILED: patch "[PATCH] NFSD: Never return NFS4ERR_FILE_OPEN when removing a" failed to apply to 6.6-stable tree

The patch below does not apply to the 6.6-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 <[email protected]>.

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-6.6.y
git checkout FETCH_HEAD
git cherry-pick -x 370345b4bd184a49ac68d6591801e5e3605b355a
# <resolve conflicts, build, test, etc.>
git commit -s
git send-email --to '<[email protected]>' --in-reply-to '2025040848-resize-avert-7b05@gregkh' --subject-prefix 'PATCH 6.6.y' HEAD^..

Possible dependencies:

thanks,

greg k-h

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

From 370345b4bd184a49ac68d6591801e5e3605b355a Mon Sep 17 00:00:00 2001
From: Chuck Lever <[email protected]>
Date: Sun, 26 Jan 2025 16:50:18 -0500
Subject: [PATCH] NFSD: Never return NFS4ERR_FILE_OPEN when removing a
directory

RFC 8881 Section 18.25.4 paragraph 5 tells us that the server should return NFS4ERR_FILE_OPEN only if the target object is an opened file. This suggests that returning this status when removing a directory will confuse NFS clients.

This is a version-specific issue; nfsd_proc_remove/rmdir() and nfsd3_proc_remove/rmdir() already return nfserr_access as appropriate.

Unfortunately there is no quick way for nfsd4_remove() to determine whether the target object is a file or not, so the check is done in in nfsd_unlink() for now.

index 749dd84bdb41..4e0a2c0549c7 100644
@@ -1930,9 +1930,17 @@ nfsd_rename(struct svc_rqst *rqstp, struct svc_fh *ffhp, char *fname, int flen,
 	return err;
 }
 
-/*
- * Unlink a file or directory
- * N.B. After this call fhp needs an fh_put
+/**
+ * nfsd_unlink - remove a directory entry
+ * @rqstp: RPC transaction context
+ * @fhp: the file handle of the parent directory to be modified
+ * @type: enforced file type of the object to be removed
+ * @fname: the name of directory entry to be removed
+ * @flen: length of @fname in octets
+ *
+ * After this call fhp needs an fh_put.
+ *
+ * Returns a generic NFS status code in network byte-order.
  */
 __be32
 nfsd_unlink(struct svc_rqst *rqstp, struct svc_fh *fhp, int type,

@@ -2006,10 +2014,14 @@ nfsd_unlink(struct svc_rqst *rqstp, struct svc_fh *fhp, int type,
 	fh_drop_write(fhp);
 out_nfserr:
 	if (host_err == -EBUSY) {
-		/* name is mounted-on. There is no perfect
-		 * error status.
+		/*
+		 * See RFC 8881 Section 18.25.4 para 4: NFSv4 REMOVE
+		 * wants a status unique to the object type.
 		 */
-		err = nfserr_file_open;
+		if (type != S_IFDIR)
+			err = nfserr_file_open;
+		else
+			err = nfserr_acces;
 	}
 out:
 	return err != nfs_ok ? err : nfserrno(host_err);