From: "Darrick J. Wong" <[email protected]>
To: Jens Axboe <[email protected]>
Cc: Al Viro <[email protected]>, Stefan Roesch <[email protected]>,
[email protected], [email protected], [email protected],
[email protected], [email protected],
[email protected], [email protected], [email protected],
Christoph Hellwig <[email protected]>
Subject: Re: [PATCH v7 15/15] xfs: Add async buffered write support
Date: Fri, 1 Jul 2022 11:05:28 -0700 [thread overview]
Message-ID: <Yr83aD0yuEwvJ7tL@magnolia> (raw)
In-Reply-To: <[email protected]>
On Fri, Jul 01, 2022 at 08:38:07AM -0600, Jens Axboe wrote:
> On 7/1/22 8:30 AM, Jens Axboe wrote:
> > On 7/1/22 8:19 AM, Jens Axboe wrote:
> >> On 6/30/22 10:39 PM, Al Viro wrote:
> >>> On Wed, Jun 01, 2022 at 02:01:41PM -0700, Stefan Roesch wrote:
> >>>> This adds the async buffered write support to XFS. For async buffered
> >>>> write requests, the request will return -EAGAIN if the ilock cannot be
> >>>> obtained immediately.
> >>>
> >>> breaks generic/471...
> >>
> >> That test case is odd, because it makes some weird assumptions about
> >> what RWF_NOWAIT means. Most notably that it makes it mean if we should
> >> instantiate blocks or not. Where did those assumed semantics come from?
> >> On the read side, we have clearly documented that it should "not wait
> >> for data which is not immediately available".
> >>
> >> Now it is possible that we're returning a spurious -EAGAIN here when we
> >> should not be. And that would be a bug imho. I'll dig in and see what's
> >> going on.
> >
> > This is the timestamp update that needs doing which will now return
> > -EAGAIN if IOCB_NOWAIT is set as it may block.
> >
> > I do wonder if we should just allow inode time updates with IOCB_NOWAIT,
> > even on the io_uring side. Either that, or passed in RWF_NOWAIT
> > semantics don't map completely to internal IOCB_NOWAIT semantics. At
> > least in terms of what generic/471 is doing, but I'm not sure who came
> > up with that and if it's established semantics or just some made up ones
> > from whomever wrote that test. I don't think they make any sense, to be
> > honest.
>
> Further support that generic/471 is just randomly made up semantics,
> it needs to special case btrfs with nocow or you'd get -EAGAIN anyway
> for that test.
>
> And it's relying on some random timing to see if this works. I really
> think that test case is just hot garbage, and doesn't test anything
> meaningful.
<shrug> I had thought that NOWAIT means "don't wait for *any*thing",
which would include timestamp updates... but then I've never been all
that clear on what specifically NOWAIT will and won't wait for. :/
--D
> --
> Jens Axboe
>
next prev parent reply other threads:[~2022-07-01 18:05 UTC|newest]
Thread overview: 51+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-06-01 21:01 [PATCH v7 00/15] io-uring/xfs: support async buffered writes Stefan Roesch
2022-06-01 21:01 ` [PATCH v7 01/15] mm: Move starting of background writeback into the main balancing loop Stefan Roesch
2022-06-01 21:01 ` [PATCH v7 02/15] mm: Move updates of dirty_exceeded into one place Stefan Roesch
2022-06-01 21:01 ` [PATCH v7 03/15] mm: Add balance_dirty_pages_ratelimited_flags() function Stefan Roesch
2022-06-01 21:01 ` [PATCH v7 04/15] iomap: Add flags parameter to iomap_page_create() Stefan Roesch
2022-06-02 16:26 ` Darrick J. Wong
2022-06-01 21:01 ` [PATCH v7 05/15] iomap: Add async buffered write support Stefan Roesch
2022-06-01 21:01 ` [PATCH v7 06/15] iomap: Return error code from iomap_write_iter() Stefan Roesch
2022-06-02 12:38 ` Matthew Wilcox
2022-06-02 17:08 ` Stefan Roesch
2022-06-06 16:39 ` Stefan Roesch
2022-06-06 19:18 ` Matthew Wilcox
2022-06-06 19:21 ` Stefan Roesch
2022-06-06 19:25 ` Matthew Wilcox
2022-06-06 19:28 ` Stefan Roesch
2022-06-06 20:30 ` Matthew Wilcox
2022-06-06 20:34 ` Stefan Roesch
2022-06-01 21:01 ` [PATCH v7 07/15] fs: Add check for async buffered writes to generic_write_checks Stefan Roesch
2022-06-01 21:01 ` [PATCH v7 08/15] fs: add __remove_file_privs() with flags parameter Stefan Roesch
2022-06-02 9:04 ` Jan Kara
2022-06-01 21:01 ` [PATCH v7 09/15] fs: Split off inode_needs_update_time and __file_update_time Stefan Roesch
2022-06-02 8:44 ` Jan Kara
2022-06-02 12:57 ` Matthew Wilcox
2022-06-02 21:04 ` Stefan Roesch
2022-06-01 21:01 ` [PATCH v7 10/15] fs: Add async write file modification handling Stefan Roesch
2022-06-02 8:44 ` Jan Kara
2022-06-02 9:06 ` Jan Kara
2022-06-02 21:00 ` Stefan Roesch
2022-06-03 10:12 ` Jan Kara
2022-06-06 16:35 ` Stefan Roesch
2022-06-01 21:01 ` [PATCH v7 11/15] fs: Optimization for concurrent file time updates Stefan Roesch
2022-06-02 8:59 ` Jan Kara
2022-06-02 21:06 ` Stefan Roesch
2022-06-01 21:01 ` [PATCH v7 12/15] io_uring: Add support for async buffered writes Stefan Roesch
2022-06-01 21:01 ` [PATCH v7 13/15] io_uring: Add tracepoint for short writes Stefan Roesch
2022-06-01 21:01 ` [PATCH v7 14/15] xfs: Specify lockmode when calling xfs_ilock_for_iomap() Stefan Roesch
2022-06-02 16:25 ` Darrick J. Wong
2022-06-01 21:01 ` [PATCH v7 15/15] xfs: Add async buffered write support Stefan Roesch
2022-07-01 4:39 ` Al Viro
2022-07-01 14:19 ` Jens Axboe
2022-07-01 14:30 ` Jens Axboe
2022-07-01 14:38 ` Jens Axboe
2022-07-01 18:05 ` Darrick J. Wong [this message]
2022-07-01 18:14 ` Jens Axboe
2022-07-05 13:47 ` Josef Bacik
2022-07-05 14:23 ` Goldwyn Rodrigues
2022-07-05 16:11 ` Christoph Hellwig
2022-06-02 8:09 ` [PATCH v7 00/15] io-uring/xfs: support async buffered writes Jens Axboe
2022-06-03 2:43 ` Dave Chinner
2022-06-03 13:04 ` Jens Axboe
2022-06-07 16:41 ` Stefan Roesch
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