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mountpoint-util: use new kernel 5.8 statx() API for determining mnt_id 

The kernel finally has a proper API to determine the mnt_id of a file.
Let's use it.

This adds support for the STATX_MNT_ID field of statx(), added in
kernel 5.8.
This commit is contained in:
Lennart Poettering 2020-08-05 23:28:21 +02:00
parent ffaf45e4f3
commit 69b3fa14cd
3 changed files with 62 additions and 25 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

62
src/basic/missing_stat.h
View File

@ -8,38 +8,47 @@
#include <linux/stat.h>
#endif
/* a528d35e8bfcc521d7cb70aaf03e1bd296c8493f (4.11) */
/* Thew newest definition we are aware of (fa2fcf4f1df1559a0a4ee0f46915b496cc2ebf60; 5.8) */
#define STATX_DEFINITION { \
__u32 stx_mask; \
__u32 stx_blksize; \
__u64 stx_attributes; \
__u32 stx_nlink; \
__u32 stx_uid; \
__u32 stx_gid; \
__u16 stx_mode; \
__u16 __spare0[1]; \
__u64 stx_ino; \
__u64 stx_size; \
__u64 stx_blocks; \
__u64 stx_attributes_mask; \
struct statx_timestamp stx_atime; \
struct statx_timestamp stx_btime; \
struct statx_timestamp stx_ctime; \
struct statx_timestamp stx_mtime; \
__u32 stx_rdev_major; \
__u32 stx_rdev_minor; \
__u32 stx_dev_major; \
__u32 stx_dev_minor; \
__u64 stx_mnt_id; \
__u64 __spare2; \
__u64 __spare3[12]; \
}
#if !HAVE_STRUCT_STATX
struct statx_timestamp {
__s64 tv_sec;
__u32 tv_nsec;
__s32 __reserved;
};
struct statx {
__u32 stx_mask;
__u32 stx_blksize;
__u64 stx_attributes;
__u32 stx_nlink;
__u32 stx_uid;
__u32 stx_gid;
__u16 stx_mode;
__u16 __spare0[1];
__u64 stx_ino;
__u64 stx_size;
__u64 stx_blocks;
__u64 stx_attributes_mask;
struct statx_timestamp stx_atime;
struct statx_timestamp stx_btime;
struct statx_timestamp stx_ctime;
struct statx_timestamp stx_mtime;
__u32 stx_rdev_major;
__u32 stx_rdev_minor;
__u32 stx_dev_major;
__u32 stx_dev_minor;
__u64 __spare2[14];
};
struct statx STATX_DEFINITION;
#endif
/* Always define the newest version we are aware of as a distinct type, so that we can use it even if glibc
* defines an older definition */
struct new_statx STATX_DEFINITION;
/* a528d35e8bfcc521d7cb70aaf03e1bd296c8493f (4.11) */
#ifndef STATX_BTIME
#define STATX_BTIME 0x00000800U
@ -49,3 +58,8 @@ struct statx {
#ifndef AT_STATX_DONT_SYNC
#define AT_STATX_DONT_SYNC 0x4000
#endif
/* fa2fcf4f1df1559a0a4ee0f46915b496cc2ebf60 (5.8) */
#ifndef STATX_MNT_ID
#define STATX_MNT_ID 0x00001000U
#endif

2
src/basic/missing_syscall.h
View File

@ -482,7 +482,7 @@ static inline ssize_t missing_statx(int dfd, const char *filename, unsigned flag
# endif
}
# define statx missing_statx
# define statx(dfd, filename, flags, mask, buffer) missing_statx(dfd, filename, flags, mask, buffer)
#endif
#if !HAVE_SET_MEMPOLICY

23
src/basic/mountpoint-util.c
View File

@ -8,6 +8,8 @@
#include "fd-util.h"
#include "fileio.h"
#include "fs-util.h"
#include "missing_stat.h"
#include "missing_syscall.h"
#include "mountpoint-util.h"
#include "parse-util.h"
#include "path-util.h"
@ -283,8 +285,29 @@ int path_is_mount_point(const char *t, const char *root, int flags) {
}
int path_get_mnt_id(const char *path, int *ret) {
union {
struct statx sx;
struct new_statx nsx;
} buf
#if HAS_FEATURE_MEMORY_SANITIZER
= {}
# warning "Explicitly initializing struct statx, to work around msan limitation. Please remove as soon as msan has been updated to not require this."
#endif
;
int r;
if (statx(AT_FDCWD, path, AT_SYMLINK_NOFOLLOW|AT_NO_AUTOMOUNT, STATX_MNT_ID, &buf.sx) < 0) {
if (!ERRNO_IS_NOT_SUPPORTED(errno) && !ERRNO_IS_PRIVILEGE(errno))
return -errno;
/* Fall back to name_to_handle_at() and then fdinfo if statx is not supported or we lack
* privileges */
} else if (FLAGS_SET(buf.nsx.stx_mask, STATX_MNT_ID)) {
*ret = buf.nsx.stx_mnt_id;
return 0;
}
r = name_to_handle_at_loop(AT_FDCWD, path, NULL, ret, 0);
if (IN_SET(r, -EOPNOTSUPP, -ENOSYS, -EACCES, -EPERM, -EOVERFLOW, -EINVAL)) /* kernel/fs don't support this, or seccomp blocks access, or untriggered mount, or name_to_handle_at() is flaky */
return fd_fdinfo_mnt_id(AT_FDCWD, path, 0, ret);