From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail6.bemta7.messagelabs.com (mail6.bemta7.messagelabs.com [216.82.255.55]) by kanga.kvack.org (Postfix) with ESMTP id 921556B00EE for ; Mon, 25 Jul 2011 04:19:27 -0400 (EDT) Date: Mon, 25 Jul 2011 09:19:18 +0100 From: Mel Gorman Subject: Re: [PATCH 2/8] xfs: Warn if direct reclaim tries to writeback pages Message-ID: <20110725081918.GZ5349@suse.de> References: <1311265730-5324-1-git-send-email-mgorman@suse.de> <1311265730-5324-3-git-send-email-mgorman@suse.de> <20110724113200.GA26332@infradead.org> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-15 Content-Disposition: inline In-Reply-To: <20110724113200.GA26332@infradead.org> Sender: owner-linux-mm@kvack.org List-ID: To: Christoph Hellwig Cc: Linux-MM , Rik van Riel , Jan Kara , LKML , XFS , Minchan Kim , Wu Fengguang , Johannes Weiner On Sun, Jul 24, 2011 at 07:32:00AM -0400, Christoph Hellwig wrote: > On Thu, Jul 21, 2011 at 05:28:44PM +0100, Mel Gorman wrote: > > --- a/fs/xfs/linux-2.6/xfs_aops.c > > +++ b/fs/xfs/linux-2.6/xfs_aops.c > > @@ -930,12 +930,13 @@ xfs_vm_writepage( > > * random callers for direct reclaim or memcg reclaim. We explicitly > > * allow reclaim from kswapd as the stack usage there is relatively low. > > * > > - * This should really be done by the core VM, but until that happens > > - * filesystems like XFS, btrfs and ext4 have to take care of this > > - * by themselves. > > + * This should never happen except in the case of a VM regression so > > + * warn about it. > > */ > > - if ((current->flags & (PF_MEMALLOC|PF_KSWAPD)) == PF_MEMALLOC) > > + if ((current->flags & (PF_MEMALLOC|PF_KSWAPD)) == PF_MEMALLOC) { > > + WARN_ON_ONCE(1); > > goto redirty; > > The nicer way to write this is > > if (WARN_ON(current->flags & (PF_MEMALLOC|PF_KSWAPD)) == PF_MEMALLOC) > goto redirty; > I wanted to avoid side effects if WARN_ON was compiled out similar to the care that is normally taken for BUG_ON but it's unnecessary and your version is far tidier. Do you really want WARN_ON used instead of WARN_ON_ONCE()? -- Mel Gorman SUSE Labs -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Fight unfair telecom internet charges in Canada: sign http://stopthemeter.ca/ Don't email: email@kvack.org