[PATCH 3/3] hpfs: implement the show_options method

[Mikulas Patocka <mikulas@twibright.com>]

The HPFS filesystem used generic_show_options to produce string that is
displayed in /proc/mounts. However, there is problem that the options may
disappear after remount. If we mount the filesystem with option1 and then
remount it with option2, /proc/mounts should show both option1 and
option2, however it only shows option2 because the whole option string is
replaced with replace_mount_options in hpfs_remount_fs.

To fix this bug, implement the hpfs_show_options function that prints
options that are currently selected.

Signed-off-by: Mikulas Patocka <mpatocka@redhat.com>
Cc: stable@vger.kernel.org

---
 fs/hpfs/super.c |   43 ++++++++++++++++++++++++++++++++-----------
 1 file changed, 32 insertions(+), 11 deletions(-)

Index: linux-4.6/fs/hpfs/super.c
===================================================================
--- linux-4.6.orig/fs/hpfs/super.c	2016-05-23 19:02:35.000000000 +0200
+++ linux-4.6/fs/hpfs/super.c	2016-05-23 19:18:22.000000000 +0200
@@ -15,6 +15,7 @@
 #include <linux/sched.h>
 #include <linux/bitmap.h>
 #include <linux/slab.h>
+#include <linux/seq_file.h>
 
 /* Mark the filesystem dirty, so that chkdsk checks it when os/2 booted */
 
@@ -455,10 +456,6 @@ static int hpfs_remount_fs(struct super_
 	int lowercase, eas, chk, errs, chkdsk, timeshift;
 	int o;
 	struct hpfs_sb_info *sbi = hpfs_sb(s);
-	char *new_opts = kstrdup(data, GFP_KERNEL);
-
-	if (data && !new_opts)
-		return -ENOMEM;
 
 	sync_filesystem(s);
 
@@ -495,18 +492,44 @@ static int hpfs_remount_fs(struct super_
 
 	if (!(*flags & MS_RDONLY)) mark_dirty(s, 1);
 
-	if (new_opts)
-		replace_mount_options(s, new_opts);
-
 	hpfs_unlock(s);
 	return 0;
 
 out_err:
 	hpfs_unlock(s);
-	kfree(new_opts);
 	return -EINVAL;
 }
 
+static int hpfs_show_options(struct seq_file *seq, struct dentry *root)
+{
+	struct hpfs_sb_info *sbi = hpfs_sb(root->d_sb);
+
+	seq_printf(seq, ",uid=%u", from_kuid_munged(&init_user_ns, sbi->sb_uid));
+	seq_printf(seq, ",gid=%u", from_kgid_munged(&init_user_ns, sbi->sb_gid));
+	seq_printf(seq, ",umask=%03o", (~sbi->sb_mode & 0777));
+	if (sbi->sb_lowercase)
+		seq_printf(seq, ",case=lower");
+	if (!sbi->sb_chk)
+		seq_printf(seq, ",check=none");
+	if (sbi->sb_chk == 2)
+		seq_printf(seq, ",check=strict");
+	if (!sbi->sb_err)
+		seq_printf(seq, ",errors=continue");
+	if (sbi->sb_err == 2)
+		seq_printf(seq, ",errors=panic");
+	if (!sbi->sb_chkdsk)
+		seq_printf(seq, ",chkdsk=no");
+	if (sbi->sb_chkdsk == 2)
+		seq_printf(seq, ",chkdsk=always");
+	if (!sbi->sb_eas)
+		seq_printf(seq, ",eas=no");
+	if (sbi->sb_eas == 1)
+		seq_printf(seq, ",eas=ro");
+	if (sbi->sb_timeshift)
+		seq_printf(seq, ",timeshift=%d", sbi->sb_timeshift);
+	return 0;
+}
+
 /* Super operations */
 
 static const struct super_operations hpfs_sops =
@@ -517,7 +540,7 @@ static const struct super_operations hpf
 	.put_super	= hpfs_put_super,
 	.statfs		= hpfs_statfs,
 	.remount_fs	= hpfs_remount_fs,
-	.show_options	= generic_show_options,
+	.show_options	= hpfs_show_options,
 };
 
 static int hpfs_fill_super(struct super_block *s, void *options, int silent)
@@ -540,8 +563,6 @@ static int hpfs_fill_super(struct super_
 
 	int o;
 
-	save_mount_options(s, options);
-
 	sbi = kzalloc(sizeof(*sbi), GFP_KERNEL);
 	if (!sbi) {
 		return -ENOMEM;