Messages in this thread | | | From | Nikita Danilov <> | Date | Thu, 21 Aug 2003 13:00:22 +0400 | Subject | Re: posix_fallocate question again |
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Andrew Morton writes: > "Chen, Kenneth W" <kenneth.w.chen@intel.com> wrote: > > > > This has been brought up by Ulrich more than 3 years ago: > > http://marc.theaimsgroup.com/?l=linux-kernel&m=95569775802945&w=2 > > A decent fallocate() implementation requires that the underlying fs has a > permanent representation of blocks which are in an "allocated, > uninitialised" state. afaik XFS is the only such filesystem. > > It's a fair bit of work for what doesn't really sound a very useful > feature. Doing it in libc is reasonable. Probably the libc implementation > could be improved by using ioctl(FIBMAP) and O_DIRECT to mimimise IO and > CPU utilisation.
fallocate() will be useful when writing into file through mmap(). Currently kernel can just drop dirtied page at any moment (if ->writepage() fails with -ENOSPC), so the only safe way to modify file through mmap() is by using mlock().
> > > Is there anytime soon that kernel 2.6 will have such functionality? > > Nope. >
Nikita.
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