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copy: drop COPY_REFLINK

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Reflinking is a safe optimization whenever the source and destination are
regular, seekable files on a filesystem that supports cloning. Requiring each
caller to opt in through COPY_REFLINK adds flag plumbing without changing the
necessary fallback behavior.

Drop COPY_REFLINK, renumber the remaining flags, and have copy_bytes_full()
unconditionally try FICLONE or FICLONERANGE before entering its normal copy
loop. Isolate the clone attempt and its file-offset bookkeeping in a helper so
copy_bytes_full() only has to handle its cloned, unavailable, and error results.
A successful clone therefore completes in one operation, while an unsupported
or rejected clone falls back to progress-limited copy_file_range(), sendfile(),
or buffered copying. Keep the public reflink helpers for operations that
specifically require clone semantics.

Existing test-copy coverage exercises both bounded and unbounded regular-file
copies through copy_bytes_full().

Signed-off-by: Daan De Meyer <daan@amutable.com>
This commit is contained in:
Daan De Meyer
2026-07-15 12:12:40 +02:00
committed by Zbigniew Jędrzejewski-Szmek
parent 28b1e4ea16
commit 5a12005c83
28 changed files with 191 additions and 173 deletions
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src/nspawn/nspawn.c
+4 -4
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@@ -1877,7 +1877,7 @@ static int setup_timezone(const char *dest) {
case TIMEZONE_COPY:
/* If mounting failed, try to copy */
r = copy_file_atomic("/etc/localtime", where, 0644, COPY_REFLINK|COPY_REPLACE);
r = copy_file_atomic("/etc/localtime", where, 0644, COPY_REPLACE);
if (r < 0) {
log_full_errno(ERRNO_IS_NEG_FS_WRITE_REFUSED(r) ? LOG_DEBUG : LOG_WARNING, r,
"Failed to copy /etc/localtime to %s, ignoring: %m", where);
@@ -2005,9 +2005,9 @@ static int setup_resolv_conf(const char *dest) {
}
if (IN_SET(m, RESOLV_CONF_REPLACE_HOST, RESOLV_CONF_REPLACE_STATIC, RESOLV_CONF_REPLACE_UPLINK, RESOLV_CONF_REPLACE_STUB))
r = copy_file_atomic(what, where, 0644, COPY_REFLINK|COPY_REPLACE);
r = copy_file_atomic(what, where, 0644, COPY_REPLACE);
else
r = copy_file(what, where, O_TRUNC|O_NOFOLLOW, 0644, COPY_REFLINK);
r = copy_file(what, where, O_TRUNC|O_NOFOLLOW, 0644, /* copy_flags= */ 0);
if (r < 0) {
/* If the file already exists as symlink, let's suppress the warning, under the assumption that
* resolved or something similar runs inside and the symlink points there.
@@ -6474,7 +6474,7 @@ static int run(int argc, char *argv[]) {
{
BLOCK_SIGNALS(SIGINT);
r = copy_file(arg_image, np, O_EXCL, arg_read_only ? 0400 : 0600,
COPY_REFLINK|COPY_CRTIME|COPY_SIGINT|COPY_NOCOW_AFTER);
COPY_CRTIME|COPY_SIGINT|COPY_NOCOW_AFTER);
}
if (r == -EINTR) {
log_error_errno(r, "Interrupted while copying image file to %s, removed again.", np);