Unverified Commit 44010543 authored by Jeff Layton's avatar Jeff Layton Committed by Christian Brauner
Browse files

fs: add the ability for statmount() to report the sb_source 



/proc/self/mountinfo displays the source for the mount, but statmount()
doesn't yet have a way to return it. Add a new STATMOUNT_SB_SOURCE flag,
claim the 32-bit __spare1 field to hold the offset into the str[] array.

Reviewed-by: default avatarJan Kara <jack@suse.cz>
Signed-off-by: default avatarJeff Layton <jlayton@kernel.org>
Link: https://lore.kernel.org/r/20241111-statmount-v4-3-2eaf35d07a80@kernel.org


Acked-by: default avatarMiklos Szeredi <mszeredi@redhat.com>
Signed-off-by: default avatarChristian Brauner <brauner@kernel.org>
parent ed9d95f6

fs/namespace.c

+35 −1
Original line number Diff line number Diff line
@@ -5012,6 +5012,32 @@ static void statmount_fs_subtype(struct kstatmount *s, struct seq_file *seq) 
		seq_puts(seq, sb->s_subtype);

}



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

{

	struct super_block *sb = s->mnt->mnt_sb;

	struct mount *r = real_mount(s->mnt);



	if (sb->s_op->show_devname) {

		size_t start = seq->count;

		int ret;



		ret = sb->s_op->show_devname(seq, s->mnt->mnt_root);

		if (ret)

			return ret;



		if (unlikely(seq_has_overflowed(seq)))

			return -EAGAIN;



		/* Unescape the result */

		seq->buf[seq->count] = '\0';

		seq->count = start;

		seq_commit(seq, string_unescape_inplace(seq->buf + start, UNESCAPE_OCTAL));

	} else if (r->mnt_devname) {

		seq_puts(seq, r->mnt_devname);

	}

	return 0;

}



static void statmount_mnt_ns_id(struct kstatmount *s, struct mnt_namespace *ns)

{

	s->sm.mask |= STATMOUNT_MNT_NS_ID;
@@ -5075,6 +5101,10 @@ static int statmount_string(struct kstatmount *s, u64 flag) 
		sm->fs_subtype = start;

		statmount_fs_subtype(s, seq);

		break;

	case STATMOUNT_SB_SOURCE:

		sm->sb_source = start;

		ret = statmount_sb_source(s, seq);

		break;

	default:

		WARN_ON_ONCE(true);

		return -EINVAL;
@@ -5223,6 +5253,9 @@ static int do_statmount(struct kstatmount *s, u64 mnt_id, u64 mnt_ns_id, 
	if (!err && s->mask & STATMOUNT_FS_SUBTYPE)

		err = statmount_string(s, STATMOUNT_FS_SUBTYPE);



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

		err = statmount_string(s, STATMOUNT_SB_SOURCE);



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

		statmount_mnt_ns_id(s, ns);
@@ -5244,7 +5277,8 @@ 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_MNT_OPTS | STATMOUNT_FS_SUBTYPE)

			      STATMOUNT_FS_TYPE | STATMOUNT_MNT_OPTS | \

			      STATMOUNT_FS_SUBTYPE | STATMOUNT_SB_SOURCE)



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
@@ -174,7 +174,7 @@ struct statmount { 
	__u32 mnt_point;	/* [str] Mountpoint relative to current root */

	__u64 mnt_ns_id;	/* ID of the mount namespace */

	__u32 fs_subtype;	/* [str] Subtype of fs_type (if any) */

	__u32 __spare1[1];

	__u32 sb_source;	/* [str] Source string of the mount */

	__u64 __spare2[48];

	char str[];		/* Variable size part containing strings */

};
@@ -210,6 +210,7 @@ struct mnt_id_req { 
#define STATMOUNT_MNT_NS_ID		0x00000040U	/* Want/got mnt_ns_id */

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

#define STATMOUNT_FS_SUBTYPE		0x00000100U	/* Want/got fs_subtype */

#define STATMOUNT_SB_SOURCE		0x00000200U	/* Want/got sb_source */



/*

 * Special @mnt_id values that can be passed to listmount