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SubjectRe: [patch 15/26] Slab defrag: Support generic defragmentation for inode slab caches
On Tue, 26 Jun 2007 12:28:50 -0700 (PDT)
Christoph Lameter <clameter@sgi.com> wrote:

> On Tue, 26 Jun 2007, Andrew Morton wrote:
>
> > Yes, this is tricky stuff. I have vague ancestral memories that the sort
> > of inode work which you refer to here can cause various deadlocks, lockdep
> > warnings and such nasties when if we attempt to call it from the wrong
> > context (ie: from within fs code).
>
> Right. Michael's test flushed one such issue out.
>
> > Possibly we could prevent that by skipping all this code if the caller
> > didn't have __GFP_FS.
>
> There is no check in vmscan.c as I thought earlier.
>
>
> Slab defragmentation: Only perform slab defrag if __GFP_FS is clear
>
> Avoids slab defragmentation be triggered from filesystem operations.
>
> Signed-off-by: Christoph Lameter <clameter@sgi.com>
>
> ---
> mm/vmscan.c | 5 +++--
> 1 file changed, 3 insertions(+), 2 deletions(-)
>
> Index: linux-2.6.22-rc4-mm2/mm/vmscan.c
> ===================================================================
> --- linux-2.6.22-rc4-mm2.orig/mm/vmscan.c 2007-06-26 12:25:28.000000000 -0700
> +++ linux-2.6.22-rc4-mm2/mm/vmscan.c 2007-06-26 12:26:18.000000000 -0700
> @@ -233,8 +233,9 @@ unsigned long shrink_slab(unsigned long
> shrinker->nr += total_scan;
> }
> up_read(&shrinker_rwsem);
> - kmem_cache_defrag(sysctl_slab_defrag_ratio,
> - zone ? zone_to_nid(zone) : -1);
> + if (!(gfp_mask & __GFP_FS))
> + kmem_cache_defrag(sysctl_slab_defrag_ratio,
> + zone ? zone_to_nid(zone) : -1);
> return ret;
> }

This is inverted: __GFP_FS is set if we may perform fs operations.
-
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