linux-kernel - Re: [PATCH] loop: Disable fallocate() zero and discard if not supported

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [day] [month] [year] [list]

Message-ID: <ZmcKUgJXc9MOLvqj@infradead.org>
Date: Mon, 10 Jun 2024 07:14:42 -0700
From: Christoph Hellwig <hch@...radead.org>
To: Cyril Hrubis <chrubis@...e.cz>
Cc: Christoph Hellwig <hch@...radead.org>, Jens Axboe <axboe@...nel.dk>,
	linux-block@...r.kernel.org, linux-kernel@...r.kernel.org,
	Jan Kara <jack@...e.cz>
Subject: Re: [PATCH] loop: Disable fallocate() zero and discard if not
 supported

On Mon, Jun 10, 2024 at 04:13:23PM +0200, Cyril Hrubis wrote:
> Do we need noinline attribute for the function as well or unlikely() in
> the if condition?

unlikely sounds like the right thing here.

> > (and maybe one day we figure out a way for the file system to
> > advertise what fallocate modes it actually supports..)
> 
> One of my ideas was to try fallocate() with zero size in the
> loop_reconfigure_limits() to see if we get EOPNOTSUPP but for that to
> work we would have to make sure that we do not bail early on zero size
> in the vfs layer...

And the VFS layer doesn't know, it has to go all the way into the
file system..