On 22.06.26 10:46, Yingying Chen wrote:
On Mon, Jun 22, 2026 at 3:20 PM Peter Eisentraut <[email protected]
<mailto:[email protected]>> wrote:
While checking return/error handling of file system calls, I found that
the copy_file_range() call in pg_combinebackup has a potential problem.
If copy_file_range() returns 0, which is a documented condition, then
the loop never makes progress and could spin forever.
The other uses of copy_file_range() in the tree are surrounded by
different logic and don't appear to have this problem.
My suggested fix is to make a return value of 0 an error. It most
likely indicates that the source file has an unexpected size.
Hi, Peter,
Thanks for the patch. I agree wb==0 should be treated as an error, so
the fix direction looks good to me.
Thanks, I have committed the patch and backpatched it.
I have a small comment:
====
wb = copy_file_range(s->fd, &off, wfd, NULL, BLCKSZ - nwritten, 0);
if (wb < 0)
pg_fatal("error while copying file range from \"%s\" to
\"%s\": %m",
s->filename, output_filename);
else if (wb == 0)
pg_fatal("unexpected end of file while copying file
range from \"%s\" to \"%s\"",
s->filename, output_filename);
As copy_file_range copies from s->fd, should pg_fatal just s->filename
in the error message? In that case, input_filename is no longer used in
write_reconstructed_file(), then it might be removed from the argument list.
Yes, interesting. I notice that the input_filename function argument
wasn't used in the first commit dc212340058. Only later when the
copy_file_range() support was added (commit ac811015513), it became
used. Maybe input_filename is fully redundant with s->filename, but
this isn't very thoroughly documented, so I'm not sure.
