Re: [PATCH 4/7] xfs: Implement fallocate query support mode

Lukas Czerner
2017-09-19T08:15:43Z

On Mon, Sep 18, 2017 at 10:56:51AM -0700, Christoph Hellwig wrote:
> This seems to miss any explanation and 6 out of 7 patches.

See linux-fsdevel for entire patch set.
https://www.spinics.net/lists/linux-fsdevel/msg115740.html

>
> That being said, I really detest adding weird query modes to random
> syscalls. We should expose capabilities through the interface that
> was designed for such things: (f)pathconf, as there are a lot more
> important parameters we currently fail to expose to userspace to
> start with.

(f)pathconf on it's own is useless because I need to get this
information directly from the file system. Supported fallocate modes can
differ with inode flags (encrypted files, extent/indirect based files on
ext4). I also need in-kernel interface.

That's why I though fallocate is the convenient place to put this. I
have not looked to it, but other option might be to use fstat to get
this.

-Lukas