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, 30 insertions, 9 deletions

diff --git a/fs/namespace.c b/fs/namespace.c
index dffe6f49ab93..75d843ae46d2 100644
--- a/fs/namespace.c
+++ b/fs/namespace.c
@@ -978,7 +978,13 @@ static int show_vfsmnt(struct seq_file *m, void *v)
         int err = 0;
         struct path mnt_path = { .dentry = mnt->mnt_root, .mnt = mnt };
 
-        mangle(m, mnt->mnt_devname ? mnt->mnt_devname : "none");
+        if (mnt->mnt_sb->s_op->show_devname) {
+                err = mnt->mnt_sb->s_op->show_devname(m, mnt);
+                if (err)
+                        goto out;
+        } else {
+                mangle(m, mnt->mnt_devname ? mnt->mnt_devname : "none");
+        }
         seq_putc(m, ' ');
         seq_path(m, &mnt_path, " \t\n\\");
         seq_putc(m, ' ');
@@ -1025,7 +1031,12 @@ static int show_mountinfo(struct seq_file *m, void *v)
 
         seq_printf(m, "%i %i %u:%u ", mnt->mnt_id, mnt->mnt_parent->mnt_id,
                    MAJOR(sb->s_dev), MINOR(sb->s_dev));
-        seq_dentry(m, mnt->mnt_root, " \t\n\\");
+        if (sb->s_op->show_path)
+                err = sb->s_op->show_path(m, mnt);
+        else
+                seq_dentry(m, mnt->mnt_root, " \t\n\\");
+        if (err)
+                goto out;
         seq_putc(m, ' ');
         seq_path_root(m, &mnt_path, &root, " \t\n\\");
         if (root.mnt != p->root.mnt || root.dentry != p->root.dentry) {
@@ -1060,7 +1071,12 @@ static int show_mountinfo(struct seq_file *m, void *v)
         seq_puts(m, " - ");
         show_type(m, sb);
         seq_putc(m, ' ');
-        mangle(m, mnt->mnt_devname ? mnt->mnt_devname : "none");
+        if (sb->s_op->show_devname)
+                err = sb->s_op->show_devname(m, mnt);
+        else
+                mangle(m, mnt->mnt_devname ? mnt->mnt_devname : "none");
+        if (err)
+                goto out;
         seq_puts(m, sb->s_flags & MS_RDONLY ? " ro" : " rw");
         err = show_sb_opts(m, sb);
         if (err)
@@ -1086,11 +1102,15 @@ static int show_vfsstat(struct seq_file *m, void *v)
         int err = 0;
 
         /* device */
-        if (mnt->mnt_devname) {
-                seq_puts(m, "device ");
-                mangle(m, mnt->mnt_devname);
-        } else
-                seq_puts(m, "no device");
+        if (mnt->mnt_sb->s_op->show_devname) {
+                err = mnt->mnt_sb->s_op->show_devname(m, mnt);
+        } else {
+                if (mnt->mnt_devname) {
+                        seq_puts(m, "device ");
+                        mangle(m, mnt->mnt_devname);
+                } else
+                        seq_puts(m, "no device");
+        }
 
         /* mount point */
         seq_puts(m, " mounted on ");
@@ -1104,7 +1124,8 @@ static int show_vfsstat(struct seq_file *m, void *v)
         /* optional statistics */
         if (mnt->mnt_sb->s_op->show_stats) {
                 seq_putc(m, ' ');
-                err = mnt->mnt_sb->s_op->show_stats(m, mnt);
+                if (!err)
+                        err = mnt->mnt_sb->s_op->show_stats(m, mnt);
         }
 
         seq_putc(m, '\n');