Unverified Commit ed9d95f6 authored by Jeff Layton's avatar Jeff Layton Committed by Christian Brauner
Browse files

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



/proc/self/mountinfo prints out the sb->s_subtype after the type. This
is particularly useful for disambiguating FUSE mounts (at least when the
userland driver bothers to set it). Add STATMOUNT_FS_SUBTYPE and claim
one of the __spare2 fields to point to the offset into the str[] array.

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


Acked-by: default avatarMiklos Szeredi <mszeredi@redhat.com>
Signed-off-by: default avatarChristian Brauner <brauner@kernel.org>
parent 75ead69a

fs/namespace.c

+17 −2
Original line number Diff line number Diff line
@@ -5004,6 +5004,14 @@ static int statmount_fs_type(struct kstatmount *s, struct seq_file *seq) 
	return 0;

}



static void statmount_fs_subtype(struct kstatmount *s, struct seq_file *seq)

{

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



	if (sb->s_subtype)

		seq_puts(seq, sb->s_subtype);

}



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

{

	s->sm.mask |= STATMOUNT_MNT_NS_ID;
@@ -5040,7 +5048,7 @@ static int statmount_mnt_opts(struct kstatmount *s, struct seq_file *seq) 


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

{

	int ret;

	int ret = 0;

	size_t kbufsize;

	struct seq_file *seq = &s->seq;

	struct statmount *sm = &s->sm;
@@ -5063,6 +5071,10 @@ static int statmount_string(struct kstatmount *s, u64 flag) 
		sm->mnt_opts = start;

		ret = statmount_mnt_opts(s, seq);

		break;

	case STATMOUNT_FS_SUBTYPE:

		sm->fs_subtype = start;

		statmount_fs_subtype(s, seq);

		break;

	default:

		WARN_ON_ONCE(true);

		return -EINVAL;
@@ -5208,6 +5220,9 @@ static int do_statmount(struct kstatmount *s, u64 mnt_id, u64 mnt_ns_id, 
	if (!err && s->mask & STATMOUNT_MNT_OPTS)

		err = statmount_string(s, STATMOUNT_MNT_OPTS);



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

		err = statmount_string(s, STATMOUNT_FS_SUBTYPE);



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

		statmount_mnt_ns_id(s, ns);
@@ -5229,7 +5244,7 @@ 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_MNT_OPTS)

			      STATMOUNT_FS_TYPE | STATMOUNT_MNT_OPTS | STATMOUNT_FS_SUBTYPE)



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

			      struct statmount __user *buf, size_t bufsize,

include/uapi/linux/mount.h

+4 −1
Original line number Diff line number Diff line
@@ -173,7 +173,9 @@ struct statmount { 
	__u32 mnt_root;		/* [str] Root of mount relative to root of fs */

	__u32 mnt_point;	/* [str] Mountpoint relative to current root */

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

	__u64 __spare2[49];

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

	__u32 __spare1[1];

	__u64 __spare2[48];

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

};
@@ -207,6 +209,7 @@ struct mnt_id_req { 
#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 */

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



/*

 * Special @mnt_id values that can be passed to listmount