linux-ext4 - Re: [PATCH 1/5][TAKE3] fallocate() implementation on i86, x86

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Message-ID: <20070516123705.GB24299@amitarora.in.ibm.com>
Date:	Wed, 16 May 2007 18:07:05 +0530
From:	"Amit K. Arora" <aarora@...ux.vnet.ibm.com>
To:	Dave Kleikamp <shaggy@...ux.vnet.ibm.com>
Cc:	David Chinner <dgc@....com>, torvalds@...l.org,
	akpm@...ux-foundation.org, linux-fsdevel@...r.kernel.org,
	linux-kernel@...r.kernel.org, linux-ext4@...r.kernel.org,
	xfs@....sgi.com, suparna@...ibm.com, cmm@...ibm.com
Subject: Re: [PATCH 1/5][TAKE3] fallocate() implementation on i86, x86_64 and powerpc

On Wed, May 16, 2007 at 07:21:16AM -0500, Dave Kleikamp wrote:
> On Wed, 2007-05-16 at 13:16 +1000, David Chinner wrote:
> > On Wed, May 16, 2007 at 01:33:59AM +0530, Amit K. Arora wrote:
> 
> > > Following changes were made to the previous version:
> > >  1) Added description before sys_fallocate() definition.
> > >  2) Return EINVAL for len<=0 (With new draft that Ulrich pointed to,
> > >     posix_fallocate should return EINVAL for len <= 0.
> > >  3) Return EOPNOTSUPP if mode is not one of FA_ALLOCATE or FA_DEALLOCATE
> > >  4) Do not return ENODEV for dirs (let individual file systems decide if
> > >     they want to support preallocation to directories or not.
> > >  5) Check for wrap through zero.
> > >  6) Update c/mtime if fallocate() succeeds.
> > 
> > Please don't make this always happen. c/mtime updates should be dependent
> > on the mode being used and whether there is visible change to the file. If no
> > userspace visible changes to the file occurred, then timestamps should not
> > be changed.
> 
> i_blocks will be updated, so it seems reasonable to update ctime.  mtime
> shouldn't be changed, though, since the contents of the file will be
> unchanged.

I agree. Thus the ctime should change for FA_PREALLOCATE mode also
(which does not change the file size) - if we end up having this
additional mode in near future.

--
Regards,
Amit Arora
 
> > e.g. FA_ALLOCATE that changes file size requires same semantics of ftruncate()
> > extending the file, otherwise no change in timestamps should occur.
> > 
> > Cheers,
> > 
> > Dave.
> -- 
> David Kleikamp
> IBM Linux Technology Center
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