On Sun 08-03-15 16:49:26, Sasha Levin wrote:
> On 03/08/2015 04:38 PM, Michal Hocko wrote:
> > On Sat 07-03-15 13:38:08, Sasha Levin wrote:
> > [...]
> >> [ 1573.730097] ? kasan_free_pages (mm/kasan/kasan.c:301)
> >> [ 1573.788680] free_pages_prepare (mm/page_alloc.c:791)
> >> [ 1573.788680] ? free_hot_cold_page (./arch/x86/include/asm/paravirt.h:809 (discriminator 2) mm/page_alloc.c:1579 (discriminator 2))
> >> [ 1573.788680] free_hot_cold_page (mm/page_alloc.c:1543)
> >> [ 1573.788680] __free_pages (mm/page_alloc.c:2957)
> >> [ 1573.788680] ? __vunmap (mm/vmalloc.c:1460 (discriminator 2))
> >> [ 1573.788680] __vunmap (mm/vmalloc.c:1460 (discriminator 2))
> >
> > __vunmap is doing:
> > for (i = 0; i < area->nr_pages; i++) {
> > struct page *page = area->pages[i];
> >
> > BUG_ON(!page);
> > __free_page(page);
> > }
> >
> > is it possible that nr_pages is a huge number (a large vmalloc area)? I
> > do not see any cond_resched down __free_page path at least. vfree
> > delayes the call to workqueue when called from irq context and vunmap is
> > marked as might_sleep). So to me it looks like it would be safe. Something
> > for vmalloc familiar people, though.
> >
> > Anyway, the loop seems to be there since ages so I guess somebody just
> > started calling vmalloc for huge areas recently so it shown up.
>
> I might be missing something obvious here, but why does that loop exists at all?
>
> Can't we just call __free_pages() instead?
This is vmalloc so the pages are not necessarily physically contiguous,
no?
--
Michal Hocko
SUSE Labs
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