linux-kernel - Re: dirty balancing deadlock

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]

Message-ID: <20070220001620.GK6133@think.oraclecorp.com>
Date:	Mon, 19 Feb 2007 19:16:20 -0500
From:	Chris Mason <chris.mason@...cle.com>
To:	Miklos Szeredi <miklos@...redi.hu>
Cc:	akpm@...ux-foundation.org, linux-kernel@...r.kernel.org,
	linux-mm@...ck.org
Subject: Re: dirty balancing deadlock

On Mon, Feb 19, 2007 at 02:14:15AM +0100, Miklos Szeredi wrote:
> > > > In general, writepage is supposed to do work without blocking on
> > > > expensive locks that will get pdflush and dirty reclaim stuck in this
> > > > fashion.  You'll probably have to take the same approach reiserfs does
> > > > in data=journal mode, which is leaving the page dirty if fuse_get_req_wp
> > > > is going to block without making progress.
> > > 
> > > Pdflush, and dirty reclaim set wbc->nonblocking to true.
> > > balance_dirty_pages and fsync don't.  The problem here is that
> > > Andrew's patch is wrong to let balance_dirty_pages() try to write back
> > > pages from a different queue.
> > 
> > async or sync, writepage is supposed to either make progress or bail.
> > loopback aside, if the fuse call is blocking long term, you're going to
> > run into problems.
> 
> Hmm, like what?

Something a little different from what you're seeing.  Basically if the
PF_MEMALLOC paths end up waiting on a filesystem transaction, and that
transaction is waiting for more ram, the system will eventually grind to
a halt.  data=journal is the easiest way to hit it, since writepage
always logs at least 4k.

WB_SYNC_NONE and wbc->nonblocking aren't a great test, in reiser I
resorted to testing PF_MEMALLOC.

-chris

-
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/