copy: don't synthesize a 'user.crtime_usec' xattr on copy unless explicitly requested

Previously, when we'd copy an individual file we'd synthesize a
user.crtime_usec xattr with the source's creation time if we can
determine it. As the creation/birth time was until recently not
queriable form userspace this effectively just propagated the same xattr
on the source to the same xattr on the destination. However, current
kernels now allow to query the birthtime using statx() and we do make
use of that now. Which means that suddenly we started synthesizing these
xattrs much more regularly.

Doing this actually does make sense, but only in very few cases:
not for the typical regular files we copy, but certainly when dealing
with disk images. Hence, let's keep this kind of propagation, but let's
make it a flag and default to off. Then turn it on whenever we deal with
disk images, and leave it off otherwise.

This is particularly relevant as overlayfs combining a real fs, and a
tmpfs on top will result in EOPNOTSUPP when it is attempted to open a
file with xattrs for writing, as tmpfs does not support xattrs, and
hence the copy-up cannot work. Hence, let's avoid synthesizing this
needlessly, to increase compat with overlayfs.

3 files changed, 3 insertions, 3 deletions

diff --git a/src/import/export-raw.c b/src/import/export-raw.c
index 6a02b47a17..c1c946cd2b 100644
--- a/src/import/export-raw.c
+++ b/src/import/export-raw.c
@@ -223,7 +223,7 @@ static int raw_export_process(RawExport *e) {
 
 finish:
         if (r >= 0) {
-                (void) copy_times(e->input_fd, e->output_fd);
+                (void) copy_times(e->input_fd, e->output_fd, COPY_CRTIME);
                 (void) copy_xattr(e->input_fd, e->output_fd);
         }
 
diff --git a/src/import/import-raw.c b/src/import/import-raw.c
index 4b1161557d..56f3431a08 100644
--- a/src/import/import-raw.c
+++ b/src/import/import-raw.c
@@ -215,7 +215,7 @@ static int raw_import_finish(RawImport *i) {
                 return r;
 
         if (S_ISREG(i->st.st_mode)) {
-                (void) copy_times(i->input_fd, i->output_fd);
+                (void) copy_times(i->input_fd, i->output_fd, COPY_CRTIME);
                 (void) copy_xattr(i->input_fd, i->output_fd);
         }
 
diff --git a/src/import/pull-raw.c b/src/import/pull-raw.c
index 3a3e015df8..72b9054e49 100644
--- a/src/import/pull-raw.c
+++ b/src/import/pull-raw.c
@@ -368,7 +368,7 @@ static int raw_pull_make_local_copy(RawPull *i) {
                 return log_error_errno(r, "Failed to make writable copy of image: %m");
         }
 
-        (void) copy_times(i->raw_job->disk_fd, dfd);
+        (void) copy_times(i->raw_job->disk_fd, dfd, COPY_CRTIME);
         (void) copy_xattr(i->raw_job->disk_fd, dfd);
 
         dfd = safe_close(dfd);