linux-ext4 - Re: [PATCH] e4defrag: choose the best available posix

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Date:	Fri, 3 Jan 2014 06:57:48 +0200
From:	Baruch Siach <baruch@...s.co.il>
To:	Theodore Ts'o <tytso@....edu>
Cc:	linux-ext4@...r.kernel.org
Subject: Re: [PATCH] e4defrag: choose the best available posix_fadvise variant

Hi Ted,

On Thu, Jan 02, 2014 at 07:47:10PM -0500, Theodore Ts'o wrote:
> On Thu, Jan 02, 2014 at 08:43:54AM +0200, Baruch Siach wrote:
> > Use posix_fadvise64() when available. This allows 64bit offsets on 32bit
> > systems.
> > 
> > Rename the internal posix_fadvise() implementation to avoid collision with the
> > C library signature that is sometimes present event when the implementation
> > itself is not. This fixes build errors like:
> > 
> > e4defrag.c:189:2: warning: #warning Using locally defined posix_fadvise interface. [-Wcpp
> > e4defrag.c:203:12: error: conflicting types for ‘posix_fadvise’
> > 
> > Signed-off-by: Baruch Siach <baruch@...s.co.il>
> 
> Thanks, applied.

Thanks. You seem to have applied v1 of this patch without the #else comment 
fix. I'll fix this up in a follow up patch. Please push your tree so I can 
reference this commit in the log.

Another problem with this patch is that it doesn't takes into account the 
problem of passing 64bit values on 32bit architectures. See the discussion 
under NOTES in the syscall(2) man page for more information on that. I'll try 
to address this in another patch if you think it's worth it. The solution is 
likely to look quite ugly when taking the arch specific alignment requirements 
also into account. The alternative is to require C library support for 
fadvise64_64 on 32bit architectures.

What do you think?

baruch

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