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Merge patch series "fs: allow statmount to fetch the fs_subtype and sb_source"

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Jeff Layton <jlayton@kernel.org> says:

Meta has some internal logging that scrapes /proc/self/mountinfo today.
I'd like to convert it to use listmount()/statmount(), so we can do a
better job of monitoring with containers. We're missing some fields
though. This patchset adds them.

* patches from https://lore.kernel.org/r/20241111-statmount-v4-0-2eaf35d07a80@kernel.org:
  fs: add the ability for statmount() to report the sb_source
  fs: add the ability for statmount() to report the fs_subtype
  fs: don't let statmount return empty strings

Link: https://lore.kernel.org/r/20241111-statmount-v4-0-2eaf35d07a80@kernel.org
Signed-off-by: Christian Brauner <brauner@kernel.org>
This commit is contained in:
Christian Brauner 2024-11-12 14:37:27 +01:00
commit 3a6ffeb127
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GPG Key ID: 91C61BC06578DCA2
2 changed files with 67 additions and 7 deletions
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68
fs/namespace.c
View File

@ -5004,6 +5004,40 @@ 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 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;
@ -5040,33 +5074,48 @@ 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;
u32 start = seq->count;
switch (flag) {
case STATMOUNT_FS_TYPE:
sm->fs_type = seq->count;
sm->fs_type = start;
ret = statmount_fs_type(s, seq);
break;
case STATMOUNT_MNT_ROOT:
sm->mnt_root = seq->count;
sm->mnt_root = start;
ret = statmount_mnt_root(s, seq);
break;
case STATMOUNT_MNT_POINT:
sm->mnt_point = seq->count;
sm->mnt_point = start;
ret = statmount_mnt_point(s, seq);
break;
case STATMOUNT_MNT_OPTS:
sm->mnt_opts = seq->count;
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;
case STATMOUNT_SB_SOURCE:
sm->sb_source = start;
ret = statmount_sb_source(s, seq);
break;
default:
WARN_ON_ONCE(true);
return -EINVAL;
}
/*
* If nothing was emitted, return to avoid setting the flag
* and terminating the buffer.
*/
if (seq->count == start)
return ret;
if (unlikely(check_add_overflow(sizeof(*sm), seq->count, &kbufsize)))
return -EOVERFLOW;
if (kbufsize >= s->bufsize)
@ -5201,6 +5250,12 @@ 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_SB_SOURCE)
err = statmount_string(s, STATMOUNT_SB_SOURCE);
if (!err && s->mask & STATMOUNT_MNT_NS_ID)
statmount_mnt_ns_id(s, ns);
@ -5222,7 +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_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,

6
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 sb_source; /* [str] Source string of the mount */
__u64 __spare2[48];
char str[]; /* Variable size part containing strings */
};
@ -207,6 +209,8 @@ 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 */
#define STATMOUNT_SB_SOURCE 0x00000200U /* Want/got sb_source */
/*
* Special @mnt_id values that can be passed to listmount