Re: fallocate fail on btrfs

["Holger Hoffstätte" <holger.hoffstaette@googlemail.com>]

On Wed, 27 Aug 2014 15:58:49 -0700, G. Richard Bellamy wrote:

> [..snip..]

I can use fallocate on btrfs as you tried in your first post, with or 
without --keep-size, and it does the right things without errors. Running 
kernel 3.14+ (patched btrfs), util-linux-2.24.2 on Gentoo.

> There are two things going wrong here.
> 
> 1. The "open" command fallocate is using isn't passing along the O_CREAT
> flag properly.
> https://git.kernel.org/cgit/utils/util-linux/util-linux.git/tree/sys-
> utils/fallocate.c#n368
> CODE: fd = open(filename, O_RDWR | (!dig && !mode ? O_CREAT : 0), 0644);
> STRACE: open("test.test", O_RDWR) = -1 ENOENT (No such file or
> directory)

When you have fallocate.c open in cgit, go to its log and you will find a 
recent commit:

https://git.kernel.org/cgit/utils/util-linux/util-linux.git/commit/sys-
utils/fallocate.c?id=575718a04aa0c053875041dc387e360f2dcaa70d

aka: "fallocate: use O_CREAT only for the default behavior"

Seems to me you need to downgrade util-linux and/or complain to the util-
linux folks. In fact downgrade util-linux first (cfdisk in 2.25 eats 
partitions) and try fallocate again on whatever kernel you have running, 
just to rule out btrfs.

-h