copy: rework copy_file_atomic() to copy the specified file via O_TMPFILE if possible
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3f40303993
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4
TODO
4
TODO
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@ -14,6 +14,8 @@ Janitorial Clean-ups:
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* Rearrange tests so that the various test-xyz.c match a specific src/basic/xyz.c again
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* Rearrange tests so that the various test-xyz.c match a specific src/basic/xyz.c again
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* copy.c: set the right chattrs before copying files and others after
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* rework mount.c and swap.c to follow proper state enumeration/deserialization
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* rework mount.c and swap.c to follow proper state enumeration/deserialization
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semantics, like we do for device.c now
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semantics, like we do for device.c now
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@ -25,8 +27,6 @@ Features:
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* Add OnTimezoneChange= and OnTimeChange= stanzas to .timer units in order to
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* Add OnTimezoneChange= and OnTimeChange= stanzas to .timer units in order to
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schedule events based on time and timezone changes.
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schedule events based on time and timezone changes.
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* add O_TMPFILE support to copy_file_atomic()
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* nspawn: greater control over selinux label?
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* nspawn: greater control over selinux label?
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* cgroups: figure out if we can somehow communicate in a cleaner way whether a
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* cgroups: figure out if we can somehow communicate in a cleaner way whether a
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@ -681,31 +681,55 @@ int copy_file(const char *from, const char *to, int flags, mode_t mode, unsigned
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}
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}
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int copy_file_atomic(const char *from, const char *to, mode_t mode, unsigned chattr_flags, CopyFlags copy_flags) {
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int copy_file_atomic(const char *from, const char *to, mode_t mode, unsigned chattr_flags, CopyFlags copy_flags) {
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_cleanup_free_ char *t = NULL;
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_cleanup_(unlink_and_freep) char *t = NULL;
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_cleanup_close_ int fdt = -1;
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int r;
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int r;
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assert(from);
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assert(from);
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assert(to);
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assert(to);
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r = tempfn_random(to, NULL, &t);
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/* We try to use O_TMPFILE here to create the file if we can. Note that that only works if COPY_REPLACE is not
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if (r < 0)
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* set though as we need to use linkat() for linking the O_TMPFILE file into the file system but that system
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return r;
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* call can't replace existing files. Hence, if COPY_REPLACE is set we create a temporary name in the file
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* system right-away and unconditionally which we then can renameat() to the right name after we completed
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r = copy_file(from, t, O_NOFOLLOW|O_EXCL, mode, chattr_flags, copy_flags);
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* writing it. */
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if (r < 0)
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return r;
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if (copy_flags & COPY_REPLACE) {
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if (copy_flags & COPY_REPLACE) {
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r = renameat(AT_FDCWD, t, AT_FDCWD, to);
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r = tempfn_random(to, NULL, &t);
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if (r < 0)
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if (r < 0)
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r = -errno;
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return r;
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} else
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r = rename_noreplace(AT_FDCWD, t, AT_FDCWD, to);
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fdt = open(t, O_CREAT|O_EXCL|O_NOFOLLOW|O_NOCTTY|O_WRONLY|O_CLOEXEC, 0600);
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if (r < 0) {
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if (fdt < 0) {
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(void) unlink(t);
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t = mfree(t);
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return r;
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return -errno;
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}
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} else {
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fdt = open_tmpfile_linkable(to, O_WRONLY|O_CLOEXEC, &t);
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if (fdt < 0)
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return fdt;
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}
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}
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if (chattr_flags != 0)
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(void) chattr_fd(fdt, chattr_flags, (unsigned) -1);
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r = copy_file_fd(from, fdt, copy_flags);
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if (r < 0)
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return r;
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if (fchmod(fdt, mode) < 0)
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return -errno;
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if (copy_flags & COPY_REPLACE) {
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if (renameat(AT_FDCWD, t, AT_FDCWD, to) < 0)
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return -errno;
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} else {
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r = link_tmpfile(fdt, t, to);
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if (r < 0)
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return r;
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}
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t = mfree(t);
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return 0;
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return 0;
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}
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}
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@ -240,7 +240,27 @@ static void test_copy_bytes_regular_file(const char *src, bool try_reflink, uint
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unlink(fn3);
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unlink(fn3);
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}
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}
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static void test_copy_atomic(void) {
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_cleanup_(rm_rf_physical_and_freep) char *p = NULL;
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const char *q;
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int r;
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assert_se(mkdtemp_malloc(NULL, &p) >= 0);
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q = strjoina(p, "/fstab");
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r = copy_file_atomic("/etc/fstab", q, 0644, 0, COPY_REFLINK);
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if (r == -ENOENT)
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return;
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assert_se(copy_file_atomic("/etc/fstab", q, 0644, 0, COPY_REFLINK) == -EEXIST);
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assert_se(copy_file_atomic("/etc/fstab", q, 0644, 0, COPY_REPLACE) >= 0);
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}
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int main(int argc, char *argv[]) {
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int main(int argc, char *argv[]) {
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log_set_max_level(LOG_DEBUG);
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test_copy_file();
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test_copy_file();
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test_copy_file_fd();
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test_copy_file_fd();
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test_copy_tree();
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test_copy_tree();
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@ -251,6 +271,7 @@ int main(int argc, char *argv[]) {
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test_copy_bytes_regular_file(argv[0], true, 1000);
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test_copy_bytes_regular_file(argv[0], true, 1000);
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test_copy_bytes_regular_file(argv[0], false, 32000); /* larger than copy buffer size */
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test_copy_bytes_regular_file(argv[0], false, 32000); /* larger than copy buffer size */
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test_copy_bytes_regular_file(argv[0], true, 32000);
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test_copy_bytes_regular_file(argv[0], true, 32000);
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test_copy_atomic();
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return 0;
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return 0;
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}
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}
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