From: Christoph Hellwig <hch@infradead.org>
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: Mon, 27 Jul 2015 02:45:30 -0700 [thread overview]
Message-ID: <20150727094530.GA15507@infradead.org> (raw)
In-Reply-To: <CACVXFVOvnVHNtTkt_kiNZu9BuZHZ==EF4y3qXx+Qo=LHoytODQ@mail.gmail.com>
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.
next prev parent reply other threads:[~2015-07-27 9:45 UTC|newest]
Thread overview: 13+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <1437061068-26118-1-git-send-email-ming.lei@canonical.com>
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
[not found] ` <20150727084020.GA28336-wEGCiKHe2LqWVfeAwA7xHQ@public.gmane.org>
2015-07-27 9:41 ` Ming Lei
2015-07-27 9:45 ` Christoph Hellwig [this message]
[not found] ` <20150727094530.GA15507-wEGCiKHe2LqWVfeAwA7xHQ@public.gmane.org>
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
[not found] ` <CACVXFVMOuCk0bHZfrV=VZWLtgsa4oWxrpnu6aoB1LKZ50UMhZA-JsoAwUIsXosN+BqQ9rBEUg@public.gmane.org>
2015-07-29 22:08 ` Dave Chinner
2015-07-30 8:01 ` Ming Lei
[not found] ` <CACVXFVMKycx768HtAJXMgEZNjsQrNm_f3UzW9kUysSHAMM5FPQ-JsoAwUIsXosN+BqQ9rBEUg@public.gmane.org>
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
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