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

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/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: Jan Kara <jack@suse.cz>
Signed-off-by: Jeff Layton <jlayton@kernel.org>
Link: https://lore.kernel.org/r/20241111-statmount-v4-3-2eaf35d07a80@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 10:09:57 -05:00 committed by Christian Brauner
parent ed9d95f691
commit 44010543fc
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GPG Key ID: 91C61BC06578DCA2
2 changed files with 37 additions and 2 deletions
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36
fs/namespace.c
View File

@ -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,

3
include/uapi/linux/mount.h
View File

@ -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