From: "Holger Hoffstätte" <holger@applied-asynchrony.com>
To: Christoph Hellwig <hch@infradead.org>, Jan Kara <jack@suse.cz>
Cc: Dave Chinner <david@fromorbit.com>,
linux-xfs@vger.kernel.org, linux-fsdevel@vger.kernel.org,
linux-block@vger.kernel.org, hch@lst.de, rdorr@microsoft.com
Subject: Re: [PATCH 4/4] iomap: Use FUA for pure data O_DSYNC DIO writes
Date: Wed, 25 Apr 2018 00:07:07 +0200 [thread overview]
Message-ID: <2fb29b95-a39d-3ee7-249b-86614a8dcbb4@applied-asynchrony.com> (raw)
In-Reply-To: <20180424173444.GA25233@infradead.org>
On 04/24/18 19:34, Christoph Hellwig wrote:
> On Sat, Apr 21, 2018 at 02:54:05PM +0200, Jan Kara wrote:
>>> - if (iocb->ki_flags & IOCB_DSYNC)
>>> + if (iocb->ki_flags & IOCB_DSYNC) {
>>> dio->flags |= IOMAP_DIO_NEED_SYNC;
>>> + /*
>>> + * We optimistically try using FUA for this IO. Any
>>> + * non-FUA write that occurs will clear this flag, hence
>>> + * we know before completion whether a cache flush is
>>> + * necessary.
>>> + */
>>> + dio->flags |= IOMAP_DIO_WRITE_FUA;
>>> + }
>>
>> So I don't think this is quite correct. IOCB_DSYNC gets set also for O_SYNC
>> writes (in that case we also set IOCB_SYNC). And for those we cannot use
>> the FUA optimization AFAICT (definitely IOMAP_F_DIRTY isn't a safe
>> indicator of a need of full fsync for O_SYNC). Other than that the patch
>> looks good to me.
>
> Oops, good catch. I think the above if should just be
>
> if (iocb->ki_flags & (IOCB_DSYNC | IOCB_SYNC) == IOCB_DSYNC)) {
>
> and we are fine.
The above line just gives parenthesis salad errors, so why not compromise
on:
if ((iocb->ki_flags & (IOCB_DSYNC | IOCB_SYNC)) == IOCB_DSYNC) {
Unless my bit twiddling has completely left me I think this is what was
intended, and it actually compiles too.
cheers
Holger
next prev parent reply other threads:[~2018-04-24 22:17 UTC|newest]
Thread overview: 19+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-04-18 4:08 [PATCH 0/4 V2] iomap: Use FUA for O_DSYNC DIO writes Dave Chinner
2018-04-18 4:08 ` [PATCH 1/4] xfs: move generic_write_sync calls inwards Dave Chinner
2018-04-18 4:08 ` [PATCH 2/4] iomap: iomap_dio_rw() handles all sync writes Dave Chinner
2018-04-21 13:03 ` Jan Kara
2018-05-02 2:45 ` Dave Chinner
2018-05-02 14:27 ` Robert Dorr
2018-05-03 13:34 ` Jan Kara
2018-05-03 12:51 ` Jan Kara
2018-04-18 4:08 ` [PATCH 3/4] blk: add blk_queue_fua() helper function Dave Chinner
2018-04-18 10:34 ` Christoph Hellwig
2018-04-18 12:18 ` Matthew Wilcox
2018-04-18 14:23 ` Jens Axboe
2018-04-18 4:08 ` [PATCH 4/4] iomap: Use FUA for pure data O_DSYNC DIO writes Dave Chinner
2018-04-21 12:54 ` Jan Kara
2018-04-24 17:34 ` Christoph Hellwig
2018-04-24 22:07 ` Holger Hoffstätte [this message]
2018-04-25 5:20 ` Christoph Hellwig
2018-04-25 13:02 ` Jan Kara
2018-05-02 2:34 ` Dave Chinner
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