an interface for filesystem preallocation that doesn't suck?

Eric Sandeen sandeen at redhat.com
Thu Apr 2 22:37:00 UTC 2009


Eric Sandeen wrote:
> Rahul Sundaram wrote:
>> Eric Sandeen wrote:
>>> James Ralston wrote:
>>>
>>>> If the latter, is there an interface for fallocate() that doesn't have
>>>> quite as much FAIL as posix_fallocate()?
>>> yes, plain ol' fallocate(2), I think:
>>>
>>>        #include <linux/falloc.h>
>>>
>>>        long fallocate(int fd, int mode, loff_t offset, loff_t len);
>>>
>>> but you need a very recent glibc to get it:
>>>
>>> http://sourceware.org/bugzilla/show_bug.cgi?id=7083#c1
>>>
>>> it'd be great if we could get that into F11...
>>>
>>> BTW, ext4, xfs, btrfs, and ocfs2 all support ->fallocate.
>> Shouldn't we getting the new glibc and file RFE's against RPM, the
>> torrent clients etc?
> 
> Ah, just checked and it's already in our rawhide glibc, yay :)  didn't
> realize that.
> 
> http://sandeen.fedorapeople.org/utilities/fallocate.c
> 
> is a simple tool to exercise it, FWIW.

oh and (sorry for the spam)

http://sandeen.fedorapeople.org/utilities/fiemap-test-new.c

is a tool which can help show you the resulting file layout.

It needs fiemap.h which only recently started getting packaged up in
kernel-headers.

-Eric




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