How to generate a large file allocating space

Alex Bligh alex at
Sat Nov 6 19:44:22 UTC 2010

--On 6 November 2010 12:30:21 -0400 Ted Ts'o <tytso at> wrote:

> On Fri, Nov 05, 2010 at 08:14:56AM +0000, Alex Bligh wrote:
>> > Patches to do this wouldn't be that hard.  The harder part would
>> > probably be the politics on fs-devel regarding the semantics of
>> Also presumably there would be some pressure to make it work for
>> every filesystem that supported fallocate().
> No, I don't think so.  There are plenty of file systems that don't
> support fallocate(), and it's not a short step to consider adding new
> flags which might not be supported by all.

Thanks. I might have a go. Patches to linux-ext4@ ?

>> Thaks, that's really helpful. Are the extents always the leaves? IE
>> will next_leaf take me through extent by extent?
> Yes, to both questions.
>> Does your "please don't use this in production" warning apply to
>> tst_extents.c or to the whole of lib/ext2fs? The library calls
>> seem quite a good way to get the list of extents and are
>> presumably what fsck etc. use.
> No, only to tst_extents.c.
> The libext2fs is designed to be a production-quality codebase, with a
> stable ABI.  So feel free to use it in good health.  :-)

Again, thanks for that.

Alex Bligh

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