Re: [GIT PULL v2] Early SLAB fixes for 2.6.31

From: Pekka Enberg
Date: Mon Jun 15 2009 - 05:08:49 EST


On Mon, 2009-06-15 at 10:52 +0200, Nick Piggin wrote:
> > Furthermore, early boot cache sysfs setup is explicitly
> > handled in slab_sysfs_init() so I think we need something like the patch
> > below?
>
> I don't think so because keventd probably comes up before sysfs
> still is ready (in this respect the existing pre-early-slab code
> is probably still broken but just never done such early DMA
> allocations). So it just makes sense to do it all via the slab_state
> flag.
>
> Also, if you keep the deferred flag on there for early created
> slabs, then the next sysfs_add_work will try to add it again
> (after slab_sysfs_init already added it).
>
> Here
>
> ---
> mm/slub.c | 17 ++++++++++++++---
> 1 file changed, 14 insertions(+), 3 deletions(-)
>
> Index: linux-2.6/mm/slub.c
> ===================================================================
> --- linux-2.6.orig/mm/slub.c
> +++ linux-2.6/mm/slub.c
> @@ -2596,6 +2596,7 @@ static noinline struct kmem_cache *dma_k
> struct kmem_cache *s;
> char *text;
> size_t realsize;
> + unsigned long slabflags;
>
> s = kmalloc_caches_dma[index];
> if (s)
> @@ -2617,9 +2618,18 @@ static noinline struct kmem_cache *dma_k
> (unsigned int)realsize);
> s = kmalloc(kmem_size, flags & ~SLUB_DMA);
>
> + /*
> + * Must defer sysfs creation to a workqueue because we don't know
> + * what context we are called from. Before sysfs comes up, we don't
> + * need to do anything because slab_sysfs_init will start by
> + * adding all existing slabs to sysfs.
> + */
> + slabflags = SLAB_CACHE_DMA;
> + if (slab_state >= SYSFS)
> + slabflags |= __SYSFS_ADD_DEFERRED;
> +
> if (!s || !text || !kmem_cache_open(s, flags, text,
> - realsize, ARCH_KMALLOC_MINALIGN,
> - SLAB_CACHE_DMA|__SYSFS_ADD_DEFERRED, NULL)) {
> + realsize, ARCH_KMALLOC_MINALIGN, slabflags, NULL)) {
> kfree(s);
> kfree(text);
> goto unlock_out;
> @@ -2628,7 +2638,8 @@ static noinline struct kmem_cache *dma_k
> list_add(&s->list, &slab_caches);
> kmalloc_caches_dma[index] = s;
>
> - schedule_work(&sysfs_add_work);
> + if (slab_state >= SYSFS)
> + schedule_work(&sysfs_add_work);
>
> unlock_out:
> up_write(&slub_lock);

Looks good to me. Heiko, does it fix your case?

Pekka

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