Re: [[ EXT ]] [BUG REPORT] cifs/smb data corruption when writing, x86_64, kernel 6.6.71

[David Howells <dhowells@redhat.com>]

Shyam Prasad N <nspmangalore@gmail.com> wrote:

> +
> +			/* boundary check before the folio is accounted */
> +			if ((max_pages - nr_pages) <= 0 ||
> +			    (*_len + len) >= max_len ||
> +			    (*_count - nr_pages) <= 0) {
> +				folio_unlock(folio);
> +				folio_put(folio);
> +				xas_reset(xas);
> +				break;
> +			}
> +

I suspect that whilst this will work, it will mean that you can never append a
partial page to a write op; a partial page will always have to start a new RPC
call.

So if you do:

	fd = open("/cifs/foo");
	write(fd, buf, 0x1001);
	close(fd);

it will make two Write ops, one for 4K and one for 1 byte (give or take
PAGE_SIZE==4096).

David