Unverified Commit f9af549d authored by Josef Bacik's avatar Josef Bacik Committed by Christian Brauner
Browse files

fs: export mount options via statmount() 



statmount() can export arbitrary strings, so utilize the __spare1 slot
for a mnt_opts string pointer, and then support asking for and setting
the mount options during statmount().  This calls into the helper for
showing mount options, which already uses a seq_file, so fits in nicely
with our existing mechanism for exporting strings via statmount().

Signed-off-by: default avatarJosef Bacik <josef@toxicpanda.com>
Link: https://lore.kernel.org/r/3aa6bf8bd5d0a21df9ebd63813af8ab532c18276.1719257716.git.josef@toxicpanda.com


Reviewed-by: default avatarJeff Layton <jlayton@kernel.org>
[brauner: only call sb->s_op->show_options()]
Signed-off-by: default avatarChristian Brauner <brauner@kernel.org>
parent c72b6b72

fs/namespace.c

+36 −1
Original line number Diff line number Diff line
@@ -4980,6 +4980,34 @@ static void statmount_mnt_ns_id(struct kstatmount *s, struct mnt_namespace *ns) 
	s->sm.mnt_ns_id = ns->seq;

}



static int statmount_mnt_opts(struct kstatmount *s, struct seq_file *seq)

{

	struct vfsmount *mnt = s->mnt;

	struct super_block *sb = mnt->mnt_sb;

	int err;



	if (sb->s_op->show_options) {

		size_t start = seq->count;



		err = sb->s_op->show_options(seq, mnt->mnt_root);

		if (err)

			return err;



		if (unlikely(seq_has_overflowed(seq)))

			return -EAGAIN;



		if (seq->count == start)

			return 0;



		/* skip leading comma */

		memmove(seq->buf + start, seq->buf + start + 1,

			seq->count - start - 1);

		seq->count--;

	}



	return 0;

}



static int statmount_string(struct kstatmount *s, u64 flag)

{

	int ret;
@@ -5000,6 +5028,10 @@ static int statmount_string(struct kstatmount *s, u64 flag) 
		sm->mnt_point = seq->count;

		ret = statmount_mnt_point(s, seq);

		break;

	case STATMOUNT_MNT_OPTS:

		sm->mnt_opts = seq->count;

		ret = statmount_mnt_opts(s, seq);

		break;

	default:

		WARN_ON_ONCE(true);

		return -EINVAL;
@@ -5130,6 +5162,9 @@ static int do_statmount(struct kstatmount *s, u64 mnt_id, u64 mnt_ns_id, 
	if (!err && s->mask & STATMOUNT_MNT_POINT)

		err = statmount_string(s, STATMOUNT_MNT_POINT);



	if (!err && s->mask & STATMOUNT_MNT_OPTS)

		err = statmount_string(s, STATMOUNT_MNT_OPTS);



	if (!err && s->mask & STATMOUNT_MNT_NS_ID)

		statmount_mnt_ns_id(s, ns);
@@ -5151,7 +5186,7 @@ static inline bool retry_statmount(const long ret, size_t *seq_size) 
}



#define STATMOUNT_STRING_REQ (STATMOUNT_MNT_ROOT | STATMOUNT_MNT_POINT | \

			      STATMOUNT_FS_TYPE)

			      STATMOUNT_FS_TYPE | STATMOUNT_MNT_OPTS)



static int prepare_kstatmount(struct kstatmount *ks, struct mnt_id_req *kreq,

			      struct statmount __user *buf, size_t bufsize,

include/uapi/linux/mount.h

+2 −1
Original line number Diff line number Diff line
@@ -154,7 +154,7 @@ struct mount_attr { 
 */

struct statmount {

	__u32 size;		/* Total size, including strings */

	__u32 __spare1;

	__u32 mnt_opts;		/* [str] Mount options of the mount */

	__u64 mask;		/* What results were written */

	__u32 sb_dev_major;	/* Device ID */

	__u32 sb_dev_minor;
@@ -206,6 +206,7 @@ struct mnt_id_req { 
#define STATMOUNT_MNT_POINT		0x00000010U	/* Want/got mnt_point */

#define STATMOUNT_FS_TYPE		0x00000020U	/* Want/got fs_type */

#define STATMOUNT_MNT_NS_ID		0x00000040U	/* Want/got mnt_ns_id */

#define STATMOUNT_MNT_OPTS		0x00000080U	/* Want/got mnt_opts */



/*

 * Special @mnt_id values that can be passed to listmount