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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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