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Merge pull request #9199 from poettering/copy-file-atomic

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make copy_file_atomic() use O_TMPFILE to create the destination file
This commit is contained in:
Zbigniew Jędrzejewski-Szmek
2018-06-14 11:19:22 +02:00
committed by GitHub
parent 0722b35934 ec6bdf7259
commit 36ee2ececc
4 changed files with 77 additions and 24 deletions
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54
src/basic/copy.c
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@@ -718,31 +718,55 @@ int copy_file(const char *from, const char *to, int flags, mode_t mode, unsigned
}
int copy_file_atomic(const char *from, const char *to, mode_t mode, unsigned chattr_flags, CopyFlags copy_flags) {
_cleanup_free_ char *t = NULL;
_cleanup_(unlink_and_freep) char *t = NULL;
_cleanup_close_ int fdt = -1;
int r;
assert(from);
assert(to);
r = tempfn_random(to, NULL, &t);
if (r < 0)
return r;
r = copy_file(from, t, O_NOFOLLOW|O_EXCL, mode, chattr_flags, copy_flags);
if (r < 0)
return r;
/* We try to use O_TMPFILE here to create the file if we can. Note that that only works if COPY_REPLACE is not
* set though as we need to use linkat() for linking the O_TMPFILE file into the file system but that system
* call can't replace existing files. Hence, if COPY_REPLACE is set we create a temporary name in the file
* system right-away and unconditionally which we then can renameat() to the right name after we completed
* writing it. */
if (copy_flags & COPY_REPLACE) {
r = renameat(AT_FDCWD, t, AT_FDCWD, to);
r = tempfn_random(to, NULL, &t);
if (r < 0)
r = -errno;
} else
r = rename_noreplace(AT_FDCWD, t, AT_FDCWD, to);
if (r < 0) {
(void) unlink(t);
return r;
return r;
fdt = open(t, O_CREAT|O_EXCL|O_NOFOLLOW|O_NOCTTY|O_WRONLY|O_CLOEXEC, 0600);
if (fdt < 0) {
t = mfree(t);
return -errno;
}
} else {
fdt = open_tmpfile_linkable(to, O_WRONLY|O_CLOEXEC, &t);
if (fdt < 0)
return fdt;
}
if (chattr_flags != 0)
(void) chattr_fd(fdt, chattr_flags, (unsigned) -1);
r = copy_file_fd(from, fdt, copy_flags);
if (r < 0)
return r;
if (fchmod(fdt, mode) < 0)
return -errno;
if (copy_flags & COPY_REPLACE) {
if (renameat(AT_FDCWD, t, AT_FDCWD, to) < 0)
return -errno;
} else {
r = link_tmpfile(fdt, t, to);
if (r < 0)
return r;
}
t = mfree(t);
return 0;
}