[Devel] [PATCH RH7 27/32] nsfs: Add a show_path method to fix mountinfo

[Pavel Tikhomirov]

From: "Eric W. Biederman" <ebiederm at xmission.com>

Today mountinfo displays a very unhelpful "/" for nsfs files.  Add a
show_path method returning the same string as ns_dname.  This results
in a bind mount of /proc/<pid>/ns/net showing up in /proc/<pid>/mountinfo as
"net:[1234...]" instead of "/".

Signed-off-by: "Eric W. Biederman" <ebiederm at xmission.com>

(cherry picked from commit 75509fd88fbd580c793780b0001c71c3510f2726)

https://jira.sw.ru/browse/PSBM-102357

Signed-off-by: Pavel Tikhomirov <ptikhomirov at virtuozzo.com>
---
 fs/nsfs.c | 10 ++++++++++
 1 file changed, 10 insertions(+)

diff --git a/fs/nsfs.c b/fs/nsfs.c
index ade35cf01d0a..4d12343b3d0a 100644
--- a/fs/nsfs.c
+++ b/fs/nsfs.c
@@ -4,6 +4,7 @@
 #include <linux/proc_ns.h>
 #include <linux/magic.h>
 #include <linux/ktime.h>
+#include <linux/seq_file.h>
 #include <linux/user_namespace.h>
 #include <linux/nsfs.h>
 
@@ -218,9 +219,18 @@ struct file *proc_ns_fget(int fd)
 	return ERR_PTR(-EINVAL);
 }
 
+static int nsfs_show_path(struct seq_file *seq, struct dentry *dentry)
+{
+	struct inode *inode = d_inode(dentry);
+	const struct proc_ns_operations *ns_ops = dentry->d_fsdata;
+
+	return seq_printf(seq, "%s:[%lu]", ns_ops->name, inode->i_ino);
+}
+
 static const struct super_operations nsfs_ops = {
 	.statfs = simple_statfs,
 	.evict_inode = nsfs_evict,
+	.show_path = nsfs_show_path,
 };
 static struct dentry *nsfs_mount(struct file_system_type *fs_type,
 			int flags, const char *dev_name, void *data)
-- 
2.24.1