linux-kernel - Re: [PATCH 1/6] lockdep: allow to disable reclaim lockup detection

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Message-ID: <20170206143449.GD10298@dhcp22.suse.cz>
Date:   Mon, 6 Feb 2017 15:34:50 +0100
From:   Michal Hocko <mhocko@...nel.org>
To:     Matthew Wilcox <willy@...radead.org>
Cc:     Andrew Morton <akpm@...ux-foundation.org>,
        linux-fsdevel@...r.kernel.org, linux-mm@...ck.org,
        Dave Chinner <david@...morbit.com>, djwong@...nel.org,
        Theodore Ts'o <tytso@....edu>, Chris Mason <clm@...com>,
        David Sterba <dsterba@...e.cz>, Jan Kara <jack@...e.cz>,
        ceph-devel@...r.kernel.org, cluster-devel@...hat.com,
        linux-nfs@...r.kernel.org, logfs@...fs.org,
        linux-xfs@...r.kernel.org, linux-ext4@...r.kernel.org,
        linux-btrfs@...r.kernel.org, linux-mtd@...ts.infradead.org,
        reiserfs-devel@...r.kernel.org,
        linux-ntfs-dev@...ts.sourceforge.net,
        linux-f2fs-devel@...ts.sourceforge.net,
        linux-afs@...ts.infradead.org, LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 1/6] lockdep: allow to disable reclaim lockup detection

On Mon 06-02-17 06:26:41, Matthew Wilcox wrote:
> On Mon, Feb 06, 2017 at 03:07:13PM +0100, Michal Hocko wrote:
> > While we are at it also make sure that the radix tree doesn't
> > accidentaly override tags stored in the upper part of the gfp_mask.
> 
> > diff --git a/lib/radix-tree.c b/lib/radix-tree.c
> > index 9dc093d5ef39..7550be09f9d6 100644
> > --- a/lib/radix-tree.c
> > +++ b/lib/radix-tree.c
> > @@ -2274,6 +2274,8 @@ static int radix_tree_cpu_dead(unsigned int cpu)
> >  void __init radix_tree_init(void)
> >  {
> >  	int ret;
> > +
> > +	BUILD_BUG_ON(RADIX_TREE_MAX_TAGS + __GFP_BITS_SHIFT > 32);
> >  	radix_tree_node_cachep = kmem_cache_create("radix_tree_node",
> >  			sizeof(struct radix_tree_node), 0,
> >  			SLAB_PANIC | SLAB_RECLAIM_ACCOUNT,
> 
> That's going to have a conceptual conflict with some patches I have
> in flight.  I'll take this part through my radix tree patch collection.

This part is not needed for the patch, strictly speaking but I wanted to
make the code more future proof.

-- 
Michal Hocko
SUSE Labs