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] [thread-next>] [day] [month] [year] [list]
Date:   Mon, 13 Dec 2021 16:07:36 +1100
From:   Dave Chinner <>
To:     NeilBrown <>
Cc:     Andrew Morton <>,
        Mel Gorman <>,
        Philipp Reisner <>,
        Lars Ellenberg <>,
        Jan Kara <>,
        Ryusuke Konishi <>,
        "Darrick J. Wong" <>,,,,,,
Subject: Re: [PATCH 2/2] Remove bdi_congested() and wb_congested() and
 related functions

On Mon, Dec 13, 2021 at 03:14:27PM +1100, NeilBrown wrote:
> These functions are no longer useful as the only bdis that report
> congestion are in ceph, fuse, and nfs.  None of those bdis can be the
> target of the calls in drbd, ext2, nilfs2, or xfs.
> Removing the test on bdi_write_contested() in current_may_throttle()
> could cause a small change in behaviour, but only when PF_LOCAL_THROTTLE
> is set.
> So replace the calls by 'false' and simplify the code - and remove the
> functions.
> Signed-off-by: NeilBrown <>
> diff --git a/fs/xfs/xfs_buf.c b/fs/xfs/xfs_buf.c
> index 631c5a61d89b..22f73b3e888e 100644
> --- a/fs/xfs/xfs_buf.c
> +++ b/fs/xfs/xfs_buf.c
> @@ -843,9 +843,6 @@ xfs_buf_readahead_map(
>  {
>  	struct xfs_buf		*bp;
> -	if (bdi_read_congested(target->bt_bdev->bd_disk->bdi))
> -		return;

Ok, but this isn't a "throttle writeback" test here - it's trying to
avoid having speculative readahead blocking on a full request queue
instead of just skipping the readahead IO. i.e. prevent readahead
thrashing and/or adding unnecessary read load when we already have a
full read queue...

So what is the replacement for that? We want to skip the entire
buffer lookup/setup/read overhead if we're likely to block on IO
submission - is there anything we can use to do this these days?


Dave Chinner

Powered by blists - more mailing lists