Unverified Commit 3a6ffeb1 authored by Christian Brauner's avatar Christian Brauner
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Merge patch series "fs: allow statmount to fetch the fs_subtype and sb_source" 

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: default avatarChristian Brauner <brauner@kernel.org>
parents c4d7d907 44010543

fs/namespace.c

+62 −6
Original line number Diff line number Diff line
@@ -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,

include/uapi/linux/mount.h

+5 −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 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