From: Dave Chinner <david-FqsqvQoI3Ljby3iVrkZq2A@public.gmane.org>
To: Ming Lei <ming.lei-Z7WLFzj8eWMS+FvcfC7Uqw@public.gmane.org>
Cc: Christoph Hellwig <hch-wEGCiKHe2LqWVfeAwA7xHQ@public.gmane.org>,
Jens Axboe <axboe-tSWWG44O7X1aa/9Udqfwiw@public.gmane.org>,
Linux Kernel Mailing List
<linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org>,
"Justin M. Forbes"
<jforbes-rxtnV0ftBwyoClj4AeEUq9i2O/JbrIOy@public.gmane.org>,
Jeff Moyer <jmoyer-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>,
Tejun Heo <tj-DgEjT+Ai2ygdnm+yROfE0A@public.gmane.org>,
linux-api-u79uwXL29TY76Z2rM5mHXA@public.gmane.org
Subject: Re: [PATCH v7 4/6] block: loop: prepare for supporing direct IO
Date: Tue, 28 Jul 2015 08:06:22 +1000 [thread overview]
Message-ID: <20150727220622.GJ3902@dastard> (raw)
In-Reply-To: <CACVXFVMKycx768HtAJXMgEZNjsQrNm_f3UzW9kUysSHAMM5FPQ-JsoAwUIsXosN+BqQ9rBEUg@public.gmane.org>
On Mon, Jul 27, 2015 at 05:53:33AM -0400, Ming Lei wrote:
> On Mon, Jul 27, 2015 at 5:45 AM, Christoph Hellwig <hch-wEGCiKHe2LqWVfeAwA7xHQ@public.gmane.org> wrote:
> > On Mon, Jul 27, 2015 at 05:41:57AM -0400, Ming Lei wrote:
> >> > Why the hardcoded value? I suspect this should be more like:
> >> >
> >> > if (dio && inode->i_sb->s_bdev &&
> >> > (lo->lo_offset & (bdev_io_min(inode->i_sb->s_bdev) - 1)) != 0)
> >> > dio = false;
> >>
> >> The above can't work if the backing device has a bigger sector size
> >> (such as 4K), that is why loop's direct-io requires 512 min_io_size of
> >> backing device.
> >
> > Why doesn't it work? If the backing device sector size is 4k
> > and lo_offset is 0 or a multiple of 4k it should allow direct I/O,
> > and my code sniplet will allow that.
>
> Because size has to be 4k aligned too.
So check that, too. Any >= 4k block size filesystem should be doing
mostly 4k aligned and sized IO...
Cheers,
Dave.
--
Dave Chinner
david-FqsqvQoI3Ljby3iVrkZq2A@public.gmane.org
WARNING: multiple messages have this Message-ID (diff)
From: Dave Chinner <david@fromorbit.com>
To: Ming Lei <ming.lei@canonical.com>
Cc: Christoph Hellwig <hch@infradead.org>,
Jens Axboe <axboe@kernel.dk>,
Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
"Justin M. Forbes" <jforbes@fedoraproject.org>,
Jeff Moyer <jmoyer@redhat.com>, Tejun Heo <tj@kernel.org>,
linux-api@vger.kernel.org
Subject: Re: [PATCH v7 4/6] block: loop: prepare for supporing direct IO
Date: Tue, 28 Jul 2015 08:06:22 +1000 [thread overview]
Message-ID: <20150727220622.GJ3902@dastard> (raw)
In-Reply-To: <CACVXFVMKycx768HtAJXMgEZNjsQrNm_f3UzW9kUysSHAMM5FPQ@mail.gmail.com>
On Mon, Jul 27, 2015 at 05:53:33AM -0400, Ming Lei wrote:
> On Mon, Jul 27, 2015 at 5:45 AM, Christoph Hellwig <hch@infradead.org> wrote:
> > On Mon, Jul 27, 2015 at 05:41:57AM -0400, Ming Lei wrote:
> >> > Why the hardcoded value? I suspect this should be more like:
> >> >
> >> > if (dio && inode->i_sb->s_bdev &&
> >> > (lo->lo_offset & (bdev_io_min(inode->i_sb->s_bdev) - 1)) != 0)
> >> > dio = false;
> >>
> >> The above can't work if the backing device has a bigger sector size
> >> (such as 4K), that is why loop's direct-io requires 512 min_io_size of
> >> backing device.
> >
> > Why doesn't it work? If the backing device sector size is 4k
> > and lo_offset is 0 or a multiple of 4k it should allow direct I/O,
> > and my code sniplet will allow that.
>
> Because size has to be 4k aligned too.
So check that, too. Any >= 4k block size filesystem should be doing
mostly 4k aligned and sized IO...
Cheers,
Dave.
--
Dave Chinner
david@fromorbit.com
next prev parent reply other threads:[~2015-07-27 22:06 UTC|newest]
Thread overview: 27+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-07-16 15:37 [PATCH v7 0/6] block: loop: improve loop with AIO Ming Lei
2015-07-16 15:37 ` [PATCH v7 1/6] fs: direct-io: don't dirtying pages for ITER_BVEC/ITER_KVEC direct read Ming Lei
2015-07-16 16:48 ` Dave Kleikamp
2015-07-16 15:37 ` [PATCH v7 2/6] block: loop: set QUEUE_FLAG_NOMERGES for request queue of loop Ming Lei
2015-07-16 15:37 ` [PATCH v7 3/6] block: loop: use kthread_work Ming Lei
2015-07-16 15:37 ` [PATCH v7 4/6] block: loop: prepare for supporing direct IO Ming Lei
[not found] ` <1437061068-26118-5-git-send-email-ming.lei-Z7WLFzj8eWMS+FvcfC7Uqw@public.gmane.org>
2015-07-27 8:40 ` Christoph Hellwig
2015-07-27 8:40 ` Christoph Hellwig
[not found] ` <20150727084020.GA28336-wEGCiKHe2LqWVfeAwA7xHQ@public.gmane.org>
2015-07-27 9:41 ` Ming Lei
2015-07-27 9:41 ` Ming Lei
2015-07-27 9:45 ` Christoph Hellwig
[not found] ` <20150727094530.GA15507-wEGCiKHe2LqWVfeAwA7xHQ@public.gmane.org>
2015-07-27 9:53 ` Ming Lei
2015-07-27 9:53 ` Ming Lei
2015-07-27 17:33 ` Christoph Hellwig
2015-07-29 7:33 ` Ming Lei
2015-07-29 8:41 ` Dave Chinner
2015-07-29 11:21 ` Ming Lei
2015-07-29 11:21 ` Ming Lei
[not found] ` <CACVXFVMOuCk0bHZfrV=VZWLtgsa4oWxrpnu6aoB1LKZ50UMhZA-JsoAwUIsXosN+BqQ9rBEUg@public.gmane.org>
2015-07-29 22:08 ` Dave Chinner
2015-07-29 22:08 ` Dave Chinner
2015-07-30 8:01 ` Ming Lei
2015-07-30 8:01 ` Ming Lei
[not found] ` <CACVXFVMKycx768HtAJXMgEZNjsQrNm_f3UzW9kUysSHAMM5FPQ-JsoAwUIsXosN+BqQ9rBEUg@public.gmane.org>
2015-07-27 22:06 ` Dave Chinner [this message]
2015-07-27 22:06 ` Dave Chinner
2015-07-16 15:37 ` [PATCH v7 5/6] block: loop: introduce ioctl command of LOOP_SET_DIRECT_IO Ming Lei
2015-07-16 15:37 ` [PATCH v7 6/6] block: loop: support DIO & AIO Ming Lei
2015-07-23 9:00 ` [PATCH v7 0/6] block: loop: improve loop with AIO Ming Lei
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