From: Matthew Wilcox <willy@infradead.org>
To: David Howells <dhowells@redhat.com>
Cc: Al Viro <viro@zeniv.linux.org.uk>,
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 14:46:03 +0100 [thread overview]
Message-ID: <YMddm2P0vD+4edBu@casper.infradead.org> (raw)
In-Reply-To: <466590.1623677832@warthog.procyon.org.uk>
On Mon, Jun 14, 2021 at 02:37:12PM +0100, David Howells wrote:
> Matthew Wilcox <willy@infradead.org> wrote:
>
> > > (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?
>
> Al Viro made such a change for Ceph - and we're writing, not reading.
I'd feel better if you said "xfstests doesn't show any new problems"
than arguing to authority.
I know the operation which triggers this path is a call to write(),
but if, say, the file is 32 bytes long, not in cache, and you write
bytes 32-63, the client must READ bytes 0-31 from the server, which
is less than a full page.
next prev parent reply other threads:[~2021-06-14 13:46 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
2021-06-14 13:37 ` David Howells
2021-06-14 13:46 ` Matthew Wilcox [this message]
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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