linux-ext4 - Re: [PATCH] Support systems without posix

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Message-ID: <CAJr8W+i3vjmVw5Bxh5pDveuXvkC_q6YkayuA8SfF=kjSLqEFAg@mail.gmail.com>
Date:	Wed, 2 May 2012 13:01:35 -0700
From:	Ken Sumrall <ksumrall@...gle.com>
To:	"Ted Ts'o" <tytso@....edu>
Cc:	Andreas Dilger <adilger@...ger.ca>,
	Ext4 Developers List <linux-ext4@...r.kernel.org>
Subject: Re: [PATCH] Support systems without posix_memalign() and memalign()

I thought this patch enabled O_DIRECT functionality on the Mac:

  http://sourceforge.net/tracker/index.php?func=detail&aid=3140289&group_id=2406&atid=102406

___
Ken


On Wed, May 2, 2012 at 12:40 PM, Ted Ts'o <tytso@....edu> wrote:
> On Wed, May 02, 2012 at 12:52:06PM -0600, Andreas Dilger wrote:
>>
>> Won't this cause e.g. the 16kB/64kB blocksize regression tests to
>> fail on MacOS?  I've been assuming that the memalign functionality
>> is only necessary for O_DIRECT, which isn't even working on MacOS,
>> so it is enough to just return an unaligned memory chunk and it
>> will work for normal buffered IO on MacOS.
>
> Hmm, good point.  What we should probably do is fix things so we only
> try to use ext2fs_get_memalign() if we are doing O_DIRECT in the first
> place, since can be be overhead using ext2fs_memalign if it's not
> needed, especially if we are using valloc().
>
> I don't want to leave ext2fs_get_memalign doing something which isn't
> as the function is documented, even if it's good enough for our
> current needs and it will just work today.  That leaves behind an
> accident waiting to happen later on --- for example if some progam
> uses ext2fs_get_memalign() for some use other than what we currently
> assume that it will be used for...
>
>                                                         - Ted
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