On Mon, Jun 14, 2021 at 02:20:25PM +0100, David Howells wrote:
> Fix afs_write_end() to correctly handle a short copy into the intended
> write region of the page. Two things are necessary:
>
> (1) If the page is not up to date, then we should just return 0
> (ie. indicating a zero-length copy). The loop in
> generic_perform_write() will go around again, possibly breaking up the
> iterator into discrete chunks.
Does this actually work? What about the situation where you're reading
the last page of a file and thus (almost) always reading fewer bytes
than a PAGE_SIZE?
> This is analogous to commit b9de313cf05fe08fa59efaf19756ec5283af672a
> for ceph.
>
> (2) The page should not have been set uptodate if it wasn't completely set
> up by netfs_write_begin() (this will be fixed in the next page), so we
> need to set PG_uptodate here in such a case.
s/page/patch/
and you have a really bad habit of breaking the layering and referring
to PG_foo. Please just refer to PageFoo. Filesystems shouldn't
care what the implementation of PageFoo is.
> + len = min_t(size_t, len, thp_size(page) - from);
> + if (!PageUptodate(page)) {
> + if (copied < len) {
> + copied = 0;
> + goto out;
> + }
> +
> + SetPageUptodate(page);
> + }
