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

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/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: Jan Kara <jack@suse.cz>
Reviewed-by: Ian Kent <raven@themaw.net>
Signed-off-by: Jeff Layton <jlayton@kernel.org>
Link: https://lore.kernel.org/r/20241111-statmount-v4-2-2eaf35d07a80@kernel.org
Acked-by: Miklos Szeredi <mszeredi@redhat.com>
Signed-off-by: Christian Brauner <brauner@kernel.org>
This commit is contained in:
Jeff Layton 2024-11-11 10:09:56 -05:00 committed by Christian Brauner
parent 75ead69a71
commit ed9d95f691
No known key found for this signature in database
GPG Key ID: 91C61BC06578DCA2
2 changed files with 21 additions and 3 deletions
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19
fs/namespace.c
View File

@ -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,

5
include/uapi/linux/mount.h
View File

@ -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