vfs: new superblock methods to override /proc/*/mount{s,info}

a) ->show_devname(m, mnt) - what to put into devname columns in mounts,
mountinfo and mountstats
b) ->show_path(m, mnt) - what to put into relative path column in mountinfo

Leaving those NULL gives old behaviour.  NFS switched to using those.

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

1 files changed, 28 insertions, 0 deletions

diff --git a/fs/nfs/super.c b/fs/nfs/super.c
index a6ab483c9ad0..79bc61fe2868 100644
--- a/fs/nfs/super.c
+++ b/fs/nfs/super.c
@@ -263,6 +263,8 @@ static match_table_t nfs_local_lock_tokens = {
 static void nfs_umount_begin(struct super_block *);
 static int  nfs_statfs(struct dentry *, struct kstatfs *);
 static int  nfs_show_options(struct seq_file *, struct vfsmount *);
+static int  nfs_show_devname(struct seq_file *, struct vfsmount *);
+static int  nfs_show_path(struct seq_file *, struct vfsmount *);
 static int  nfs_show_stats(struct seq_file *, struct vfsmount *);
 static int nfs_get_sb(struct file_system_type *, int, const char *, void *, struct vfsmount *);
 static struct dentry *nfs_xdev_mount(struct file_system_type *fs_type,
@@ -296,6 +298,8 @@ static const struct super_operations nfs_sops = {
         .evict_inode    = nfs_evict_inode,
         .umount_begin   = nfs_umount_begin,
         .show_options   = nfs_show_options,
+        .show_devname   = nfs_show_devname,
+        .show_path      = nfs_show_path,
         .show_stats     = nfs_show_stats,
         .remount_fs     = nfs_remount,
 };
@@ -366,6 +370,8 @@ static const struct super_operations nfs4_sops = {
         .evict_inode    = nfs4_evict_inode,
         .umount_begin   = nfs_umount_begin,
         .show_options   = nfs_show_options,
+        .show_devname   = nfs_show_devname,
+        .show_path      = nfs_show_path,
         .show_stats     = nfs_show_stats,
         .remount_fs     = nfs_remount,
 };
@@ -726,6 +732,28 @@ static int nfs_show_options(struct seq_file *m, struct vfsmount *mnt)
         return 0;
 }
 
+static int nfs_show_devname(struct seq_file *m, struct vfsmount *mnt)
+{
+        char *page = (char *) __get_free_page(GFP_KERNEL);
+        char *devname, *dummy;
+        int err = 0;
+        if (!page)
+                return -ENOMEM;
+        devname = nfs_path(&dummy, mnt->mnt_root, page, PAGE_SIZE);
+        if (IS_ERR(devname))
+                err = PTR_ERR(devname);
+        else
+                seq_escape(m, devname, " \t\n\\");
+        free_page((unsigned long)page);
+        return err;
+}
+
+static int nfs_show_path(struct seq_file *m, struct vfsmount *mnt)
+{
+        seq_puts(m, "/");
+        return 0;
+}
+
 /*
  * Present statistical information for this VFS mountpoint
  */