linux-kernel - Re: [RFC PATCH 0/6] Do not call ->writepage[s] from direct reclaim and use a

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: <20100616075723.GT6138@laptop>
Date:	Wed, 16 Jun 2010 17:57:23 +1000
From:	Nick Piggin <npiggin@...e.de>
To:	Rik van Riel <riel@...hat.com>
Cc:	Christoph Hellwig <hch@...radead.org>,
	Andrea Arcangeli <aarcange@...hat.com>,
	Mel Gorman <mel@....ul.ie>, linux-kernel@...r.kernel.org,
	linux-fsdevel@...r.kernel.org, linux-mm@...ck.org,
	Dave Chinner <david@...morbit.com>,
	Chris Mason <chris.mason@...cle.com>
Subject: Re: [RFC PATCH 0/6] Do not call ->writepage[s] from direct reclaim
 and use a_ops->writepages() where possible

On Tue, Jun 15, 2010 at 03:13:09PM -0400, Rik van Riel wrote:
> On 06/15/2010 12:54 PM, Christoph Hellwig wrote:
> >On Tue, Jun 15, 2010 at 12:49:49PM -0400, Rik van Riel wrote:
> >>This is already in a filesystem.  Why does ->writepage get
> >>called a second time?  Shouldn't this have a gfp_mask
> >>without __GFP_FS set?
> >
> >Why would it?  GFP_NOFS is not for all filesystem code, but only for
> >code where we can't re-enter the filesystem due to deadlock potential.
> 
> Why?   How about because you know the stack is not big enough
> to have the XFS call path on it twice? :)
> 
> Isn't the whole purpose of this patch series to prevent writepage
> from being called by the VM, when invoked from a deep callstack
> like xfs writepage?
> 
> That sounds a lot like simply wanting to not have GFP_FS...

buffered write path uses __GFP_FS by design because huge amounts
of (dirty) memory can be allocated in doing pagecache writes. If
would be nasty if that was not allowed to wait for filesystem
activity.

--
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/