posix_fallocate(2)

[Gleb Kurtsou]

On (14/04/2011 12:35), mdf at FreeBSD.org wrote:
> For work we need a functionality in our filesystem that is pretty much
> like posix_fallocate(2), so we're using the name and I've added a
> default VOP_ALLOCATE definition that does the right, but dumb, thing.
> 
> The most recent mention of this function in FreeBSD was another thread
> lamenting it's failure to exist:
> http://lists.freebsd.org/pipermail/freebsd-ports/2010-February/059268.html
> 
> The attached files are the core of the kernel implementation of the
> syscall and a default VOP for any filesystem not supporting
> VOP_ALLOCATE, which allows the syscall to work as expected but in a
> non-performant manner.  I didn't see this syscall in NetBSD or
> OpenBSD, so I plan to add it to the end of our syscall table.
> 
> What I wanted to check with -arch about was:
> 
> 1) is there still a desire for this syscall?
It looks not to play well architecturally with modern COW file systems
like ZFS and HUMMER. So potentially it can be implemented only for UFS.

> 2) is this naive implementation useful enough to serve as a default
> for all filesystems until someone with more knowledge fills them in?
Maillist ate the patch. Only man page attached.

> 3) are there any obvious bugs or missing elements?
> 
> Thanks,
> matthew


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