From: Jeff Layton <jlayton@kernel.org>
Date: Mon, 26 Jul 2021 07:07:50 -0400
Subject: ceph: add a new vxattr to return auth mds for an inode
Git-commit: 40e309de4dd84ba91b9e0549a5173ce13ef02c5e
Patch-mainline: v5.15-rc1
References: jsc#SES-1880

Add a new vxattr that shows what MDS is authoritative for an inode (if
we happen to have auth caps). If we don't have an auth cap for the inode
then just return -1.

URL: https://tracker.ceph.com/issues/1276
Signed-off-by: Jeff Layton <jlayton@kernel.org>
Reviewed-by: Luis Henriques <lhenriques@suse.de>
Signed-off-by: Ilya Dryomov <idryomov@gmail.com>
Acked-by: Luis Henriques <lhenriques@suse.com>
---
 fs/ceph/xattr.c | 19 +++++++++++++++++++
 1 file changed, 19 insertions(+)

diff --git a/fs/ceph/xattr.c b/fs/ceph/xattr.c
index 1242db8d3444..159a1ffa4f4b 100644
--- a/fs/ceph/xattr.c
+++ b/fs/ceph/xattr.c
@@ -340,6 +340,18 @@ static ssize_t ceph_vxattrcb_caps(struct ceph_inode_info *ci, char *val,
 			      ceph_cap_string(issued), issued);
 }
 
+static ssize_t ceph_vxattrcb_auth_mds(struct ceph_inode_info *ci,
+				       char *val, size_t size)
+{
+	int ret;
+
+	spin_lock(&ci->i_ceph_lock);
+	ret = ceph_fmt_xattr(val, size, "%d",
+			     ci->i_auth_cap ? ci->i_auth_cap->session->s_mds : -1);
+	spin_unlock(&ci->i_ceph_lock);
+	return ret;
+}
+
 #define CEPH_XATTR_NAME(_type, _name)	XATTR_CEPH_PREFIX #_type "." #_name
 #define CEPH_XATTR_NAME2(_type, _name, _name2)	\
 	XATTR_CEPH_PREFIX #_type "." #_name "." #_name2
@@ -473,6 +485,13 @@ static struct ceph_vxattr ceph_common_vxattrs[] = {
 		.exists_cb = NULL,
 		.flags = VXATTR_FLAG_READONLY,
 	},
+	{
+		.name = "ceph.auth_mds",
+		.name_size = sizeof("ceph.auth_mds"),
+		.getxattr_cb = ceph_vxattrcb_auth_mds,
+		.exists_cb = NULL,
+		.flags = VXATTR_FLAG_READONLY,
+	},
 	{ .name = NULL, 0 }	/* Required table terminator */
 };