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stat-util: add helper stat_inode_same() for comparing stat's st_dev/st_ino in one

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We do this all over the place, hence let's add a simple helper that does
this and particularly carefully and thoroughly.
This commit is contained in:
Lennart Poettering 2022-02-14 17:18:32 +01:00
parent d74da762a3
commit 38db6211b5
2 changed files with 14 additions and 5 deletions
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18
src/basic/stat-util.c
View File

@ -417,6 +417,18 @@ int proc_mounted(void) {
return r;
}
bool stat_inode_same(const struct stat *a, const struct stat *b) {
/* Returns if the specified stat structure references the same (though possibly modified) inode. Does
* a thorough check, comparing inode nr, backing device and if the inode is still of the same type. */
return a && b &&
(a->st_mode & S_IFMT) != 0 && /* We use the check for .st_mode if the structure was ever initialized */
((a->st_mode ^ b->st_mode) & S_IFMT) == 0 && /* same inode type */
a->st_dev == b->st_dev &&
a->st_ino == b->st_ino;
}
bool stat_inode_unmodified(const struct stat *a, const struct stat *b) {
/* Returns if the specified stat structures reference the same, unmodified inode. This check tries to
@ -428,14 +440,10 @@ bool stat_inode_unmodified(const struct stat *a, const struct stat *b) {
* about contents of the file. The purpose here is to detect file contents changes, and nothing
* else. */
return a && b &&
(a->st_mode & S_IFMT) != 0 && /* We use the check for .st_mode if the structure was ever initialized */
((a->st_mode ^ b->st_mode) & S_IFMT) == 0 && /* same inode type */
return stat_inode_same(a, b) &&
a->st_mtim.tv_sec == b->st_mtim.tv_sec &&
a->st_mtim.tv_nsec == b->st_mtim.tv_nsec &&
(!S_ISREG(a->st_mode) || a->st_size == b->st_size) && /* if regular file, compare file size */
a->st_dev == b->st_dev &&
a->st_ino == b->st_ino &&
(!(S_ISCHR(a->st_mode) || S_ISBLK(a->st_mode)) || a->st_rdev == b->st_rdev); /* if device node, also compare major/minor, because we can */
}

1
src/basic/stat-util.h
View File

@ -92,6 +92,7 @@ int device_path_parse_major_minor(const char *path, mode_t *ret_mode, dev_t *ret
int proc_mounted(void);
bool stat_inode_same(const struct stat *a, const struct stat *b);
bool stat_inode_unmodified(const struct stat *a, const struct stat *b);
int statx_fallback(int dfd, const char *path, int flags, unsigned mask, struct statx *sx);