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From: Arnd Bergmann <arnd@arndb.de>
To: Christoph Hellwig <hch@infradead.org>
Subject: Re: [RFC] Heads up on sys_fallocate()
Date: Sat, 3 Mar 2007 23:45:32 +0100
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On Friday 02 March 2007 00:38:19 Christoph Hellwig wrote:
> > Forgive me if I haven't put enough thought into it, but would it be
> > useful to create a generic_fallocate() that writes zeroed pages for any
> > non-existent pages in the range?  I don't know how glibc currently
> > implements posix_fallocate(), but maybe the kernel could do it more
> > efficiently, even in generic code.  Maybe we don't care, since the major
> > file systems can probably do something better in their own code.
>
> I'd be more happy to have the write out zeroes loop in glibc.  And
> glibc needs to have it anyway, for older kernels.

A generic_fallocate makes sense to me iff we can do it in the kernel
more significantly more efficiently than in glibc, e.g. by using only
a single page in page cache instead of one for each page to be preallocated.

If  glibc is smart enough to do an optimal implementation, I fully agree
with you.

	Arnd <><