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From: Jens Axboe <axboe@kernel.dk>
To: Al Viro <viro@zeniv.linux.org.uk>, Stefan Roesch <shr@fb.com>
Cc: io-uring@vger.kernel.org, kernel-team@fb.com, linux-mm@kvack.org,
	linux-xfs@vger.kernel.org, linux-fsdevel@vger.kernel.org,
	david@fromorbit.com, jack@suse.cz, hch@infradead.org,
	Christoph Hellwig <hch@lst.de>
Subject: Re: [PATCH v7 15/15] xfs: Add async buffered write support
Date: Fri, 1 Jul 2022 08:30:52 -0600	[thread overview]
Message-ID: <ef7c1154-b5ba-4017-f9fd-dea936a837fc@kernel.dk> (raw)
In-Reply-To: <0a75a0c4-e2e5-b403-27bc-e43872fecdc1@kernel.dk>

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.

-- 
Jens Axboe


  reply	other threads:[~2022-07-01 14:35 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 [this message]
2022-07-01 14:38         ` Jens Axboe
2022-07-01 18:05           ` Darrick J. Wong
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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