How to generate a large file allocating space
tytso at mit.edu
Sat Nov 6 16:30:21 UTC 2010
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.
> 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. It has a tst_ prefix precisely because
it's a little hacky, and it was something that I had never intended to
be installed by distributions. (I got a little burned by "filefrag",
which was never intended to be installed at distribution, which is why
the code is so hackish, and why it's not internationalized, etc.) I
just want to make sure tst_extents doesn't similarly escape.
The libext2fs is designed to be a production-quality codebase, with a
stable ABI. So feel free to use it in good health. :-)
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