Messages in this thread | | | Date | Tue, 6 Oct 2009 22:58:03 +0100 (BST) | From | Hugh Dickins <> | Subject | Re: [PATCH] adjust gfp mask passed on nested vmalloc() invocation |
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On Mon, 5 Oct 2009, Jan Beulich wrote:
> - fix a latent bug resulting from blindly or-ing in __GFP_ZERO, since > the combination of this and __GFP_HIGHMEM (possibly passed into the > function) is forbidden in interrupt context > - avoid wasting more precious resources (DMA or DMA32 pools), when > being called through vmalloc_32{,_user}() > - explicitly allow using high memory here even if the outer allocation > request doesn't allow it, unless is collides with __GFP_ZERO > > Signed-off-by: Jan Beulich <jbeulich@novell.com>
I thought vmalloc.c was a BUG_ON(in_interrupt()) zone? The locking is all spin_lock stuff, not spin_lock_irq stuff. That's probably why your "bug" has remained "latent".
Using HIGHMEM for internal arrays looks reasonable to me; but if __GFP_ZERO were a problem, wouldn't it be much cleaner to skip the "unless it collides" and #ifdef CONFIG_HIGHMEM !in_interrupt() stuff, just memset the array returned from __vmalloc_node()?
Hugh
> > --- > mm/vmalloc.c | 12 ++++++++---- > 1 file changed, 8 insertions(+), 4 deletions(-) > > --- linux-2.6.32-rc3/mm/vmalloc.c 2009-10-05 11:59:56.000000000 +0200 > +++ 2.6.32-rc3-vmalloc-nested-gfp/mm/vmalloc.c 2009-10-05 08:40:36.000000000 +0200 > @@ -1410,6 +1410,7 @@ static void *__vmalloc_area_node(struct > { > struct page **pages; > unsigned int nr_pages, array_size, i; > + gfp_t nested_gfp = (gfp_mask & GFP_RECLAIM_MASK) | __GFP_ZERO; > > nr_pages = (area->size - PAGE_SIZE) >> PAGE_SHIFT; > array_size = (nr_pages * sizeof(struct page *)); > @@ -1417,13 +1418,16 @@ static void *__vmalloc_area_node(struct > area->nr_pages = nr_pages; > /* Please note that the recursion is strictly bounded. */ > if (array_size > PAGE_SIZE) { > - pages = __vmalloc_node(array_size, gfp_mask | __GFP_ZERO, > +#ifdef CONFIG_HIGHMEM > + /* See the comment in prep_zero_page(). */ > + if (!in_interrupt()) > + nested_gfp |= __GFP_HIGHMEM; > +#endif > + pages = __vmalloc_node(array_size, nested_gfp, > PAGE_KERNEL, node, caller); > area->flags |= VM_VPAGES; > } else { > - pages = kmalloc_node(array_size, > - (gfp_mask & GFP_RECLAIM_MASK) | __GFP_ZERO, > - node); > + pages = kmalloc_node(array_size, nested_gfp, node); > } > area->pages = pages; > area->caller = caller;
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