From: Matthew Wilcox <firstname.lastname@example.org> To: David Howells <email@example.com> Cc: Al Viro <firstname.lastname@example.org>, email@example.com, firstname.lastname@example.org, email@example.com, firstname.lastname@example.org, email@example.com 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: <firstname.lastname@example.org> On Mon, Jun 14, 2021 at 02:37:12PM +0100, David Howells wrote: > Matthew Wilcox <email@example.com> 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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