[PATCH 2/4] fs: add a helper to show all the options for a mount

[Josef Bacik <josef@xxxxxxxxxxxxxx>]

In order to add the ability to export the mount options via statmount()
we need a helper to combine all the various mount option things we do
for /proc/mounts and /proc/$PID/mountinfo.  The helper for /proc/mounts
can use this helper, however mountinfo is slightly (and infuriatingly)
different, so it can only be used in one place.  This helper will be
used in a followup patch to export mount options via statmount().

Signed-off-by: Josef Bacik <josef@xxxxxxxxxxxxxx>
---
 fs/internal.h       |  5 +++++
 fs/proc_namespace.c | 25 ++++++++++++++++++-------
 2 files changed, 23 insertions(+), 7 deletions(-)

diff --git a/fs/internal.h b/fs/internal.h
index 84f371193f74..dc40c9d4173f 100644
--- a/fs/internal.h
+++ b/fs/internal.h
@@ -321,3 +321,8 @@ struct stashed_operations {
 int path_from_stashed(struct dentry **stashed, struct vfsmount *mnt, void *data,
 		      struct path *path);
 void stashed_dentry_prune(struct dentry *dentry);
+
+/*
+ * fs/proc_namespace.c
+ */
+int show_mount_opts(struct seq_file *seq, struct vfsmount *mnt);
diff --git a/fs/proc_namespace.c b/fs/proc_namespace.c
index e133b507ddf3..19bffd9d80dc 100644
--- a/fs/proc_namespace.c
+++ b/fs/proc_namespace.c
@@ -84,6 +84,22 @@ static void show_vfsmnt_opts(struct seq_file *m, struct vfsmount *mnt)
 		seq_puts(m, ",idmapped");
 }
 
+int show_mount_opts(struct seq_file *seq, struct vfsmount *mnt)
+{
+	struct dentry *dentry = mnt->mnt_root;
+	struct super_block *sb = dentry->d_sb;
+	int ret;
+
+	seq_puts(seq, __mnt_is_readonly(mnt) ? "ro" : "rw");
+	ret = show_sb_opts(seq, sb);
+	if (ret)
+		return ret;
+	show_vfsmnt_opts(seq, mnt);
+	if (sb->s_op->show_options)
+		ret = sb->s_op->show_options(seq, dentry);
+	return ret;
+}
+
 static inline void mangle(struct seq_file *m, const char *s)
 {
 	seq_escape(m, s, " \t\n\\#");
@@ -120,13 +136,8 @@ static int show_vfsmnt(struct seq_file *m, struct vfsmount *mnt)
 		goto out;
 	seq_putc(m, ' ');
 	show_type(m, sb);
-	seq_puts(m, __mnt_is_readonly(mnt) ? " ro" : " rw");
-	err = show_sb_opts(m, sb);
-	if (err)
-		goto out;
-	show_vfsmnt_opts(m, mnt);
-	if (sb->s_op->show_options)
-		err = sb->s_op->show_options(m, mnt_path.dentry);
+	seq_putc(m, ' ');
+	err = show_mount_opts(m, mnt);
 	seq_puts(m, " 0 0\n");
 out:
 	return err;
-- 
2.43.0