linux-kernel - Re: [PATCH 8/8] vm: Add an tuning knob for vm.max_writeback

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

Date:	Wed, 30 Sep 2009 14:10:30 +0200
From:	Jens Axboe <jens.axboe@...cle.com>
To:	Jan Kara <jack@...e.cz>
Cc:	Wu Fengguang <fengguang.wu@...el.com>,
	Peter Zijlstra <peterz@...radead.org>,
	Chris Mason <chris.mason@...cle.com>,
	Artem Bityutskiy <dedekind1@...il.com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"linux-fsdevel@...r.kernel.org" <linux-fsdevel@...r.kernel.org>,
	"david@...morbit.com" <david@...morbit.com>,
	"hch@...radead.org" <hch@...radead.org>,
	"akpm@...ux-foundation.org" <akpm@...ux-foundation.org>,
	Theodore Ts'o <tytso@....edu>
Subject: Re: [PATCH 8/8] vm: Add an tuning knob for vm.max_writeback_mb

On Wed, Sep 30 2009, Jan Kara wrote:
> > +void bdi_writeback_wait(struct backing_dev_info *bdi, long nr_pages)
> > +{
> > +	struct dirty_throttle_task tt = {
> > +		.nr_pages = nr_pages,
> > +		.complete = COMPLETION_INITIALIZER_ONSTACK(tt.complete),
> > +	};
> > +	struct wb_writeback_args args = {
> > +		.sync_mode	= WB_SYNC_NONE,
> > +		.nr_pages	= LONG_MAX,
> > +		.range_cyclic	= 1,
> > +		.for_background	= 1,
> > +	};
> > +	struct bdi_work work;
> > +
> > +	bdi_work_init(&work, &args);
> > +	work.state |= WS_ONSTACK;
> > +
> > +	/*
> > +	 * make sure we will be waken up by someone
> > +	 */
> > +	bdi_queue_work(bdi, &work);
>   This is wrong, you shouldn't submit the work like this because you'll
> have to wait for completion (wb_clear_pending below is just bogus). You
> should rather do bdi_start_writeback(bdi, NULL, 0).

Indeed, the above will die a horrible death fairly soon. But we can add
some "barrier" like synchronization, if you just wish to wait for
previously submitted work to have been completed.


-- 
Jens Axboe

--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/