linux-kernel - Re: [PATCH v5 7/7] add a flag for per-operation O

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Message-Id: <BF30FAEC-D4D3-4079-9ECD-2743747279BD@cam.ac.uk>
Date:	Fri, 7 Nov 2014 06:22:48 +0200
From:	Anton Altaparmakov <aia21@....ac.uk>
To:	Jeff Moyer <jmoyer@...hat.com>
Cc:	Milosz Tanski <milosz@...in.com>, linux-kernel@...r.kernel.org,
	Christoph Hellwig <hch@....de>,
	Christoph Hellwig <hch@...radead.org>,
	linux-fsdevel@...r.kernel.org, linux-aio@...ck.org,
	Mel Gorman <mgorman@...e.de>,
	Volker Lendecke <Volker.Lendecke@...net.de>,
	Tejun Heo <tj@...nel.org>, Theodore Ts'o <tytso@....edu>,
	Al Viro <viro@...iv.linux.org.uk>, linux-api@...r.kernel.org,
	Michael Kerrisk <mtk.manpages@...il.com>,
	linux-arch@...r.kernel.org, ceph-devel@...r.kernel.org,
	fuse-devel@...ts.sourceforge.net, linux-nfs@...r.kernel.org,
	ocfs2-devel@....oracle.com, linux-mm@...ck.org
Subject: Re: [PATCH v5 7/7] add a flag for per-operation O_DSYNC semantics

Hi Jeff,

> On 7 Nov 2014, at 01:46, Jeff Moyer <jmoyer@...hat.com> wrote:
> 
> Milosz Tanski <milosz@...in.com> writes:
> 
>> -		if (type == READ && (flags & RWF_NONBLOCK))
>> -			return -EAGAIN;
>> +		if (type == READ) {
>> +			if (flags & RWF_NONBLOCK)
>> +				return -EAGAIN;
>> +		} else {
>> +			if (flags & RWF_DSYNC)
>> +				return -EINVAL;
>> +		}
> 
> Minor nit, but I'd rather read something that looks like this:
> 
> 	if (type == READ && (flags & RWF_NONBLOCK))
> 		return -EAGAIN;
> 	else if (type == WRITE && (flags & RWF_DSYNC))
> 		return -EINVAL;

But your version is less logically efficient for the case where "type == READ" is true and "flags & RWF_NONBLOCK" is false because your version then has to do the "if (type == WRITE" check before discovering it does not need to take that branch either, whilst the original version does not have to do such a test at all.

Best regards,

	Anton

> I won't lose sleep over it, though.
> 
> Reviewed-by: Jeff Moyer <jmoyer@...hat.com>

-- 
Anton Altaparmakov <aia21 at cam.ac.uk> (replace at with @)
University of Cambridge Information Services, Roger Needham Building
7 JJ Thomson Avenue, Cambridge, CB3 0RB, UK

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