From: Matthew Wilcox <willy@infradead.org>
To: David Howells <dhowells@redhat.com>
Cc: jlayton@kernel.org, linux-afs@lists.infradead.org,
ceph-devel@vger.kernel.org, linux-fsdevel@vger.kernel.org,
linux-kernel@vger.kernel.org
Subject: Re: [PATCH 2/3] afs: Fix afs_write_end() to handle short writes
Date: Mon, 14 Jun 2021 14:28:14 +0100 [thread overview]
Message-ID: <YMdZbsvBNYBtZDC2@casper.infradead.org> (raw)
In-Reply-To: <162367682522.460125.5652091227576721609.stgit@warthog.procyon.org.uk>
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);
> + }
next prev parent reply other threads:[~2021-06-14 13:28 UTC|newest]
Thread overview: 15+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-06-14 13:20 [PATCH 1/3] afs: Handle len being extending over page end in write_begin/write_end David Howells
2021-06-14 13:20 ` [PATCH 2/3] afs: Fix afs_write_end() to handle short writes David Howells
2021-06-14 13:28 ` Matthew Wilcox [this message]
2021-06-14 13:37 ` David Howells
2021-06-14 13:46 ` Matthew Wilcox
2021-06-18 3:40 ` Al Viro
2021-06-14 14:04 ` David Howells
2021-06-14 14:37 ` Matthew Wilcox
2021-06-14 15:38 ` David Howells
2021-06-14 15:43 ` Matthew Wilcox
2021-06-14 21:11 ` David Howells
2021-06-14 13:20 ` [PATCH 3/3] netfs: fix test for whether we can skip read when writing beyond EOF David Howells
2021-06-15 17:01 ` Jeff Layton
2021-06-14 13:33 ` David Howells
2021-06-17 7:43 ` [PATCH 1/3] afs: Handle len being extending over page end in write_begin/write_end kernel test robot
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