| Message ID | xa1tegyfv2gw.fsf@mina86.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
On Mon, 2014-06-23 at 21:40 +0200, Michal Nazarewicz wrote: > With a kernel configured with ARM64_64K_PAGES && !TRANSPARENT_HUGEPAGE, > the following is triggered at early boot: > > SMP: Total of 8 processors activated. > devtmpfs: initialized > Unable to handle kernel NULL pointer dereference at virtual address 00000008 > pgd = fffffe0000050000 > [00000008] *pgd=00000043fba00003, *pmd=00000043fba00003, *pte=00e0000078010407 > Internal error: Oops: 96000006 [#1] SMP > Modules linked in: > CPU: 0 PID: 1 Comm: swapper/0 Not tainted 3.15.0-rc864k+ #44 > task: fffffe03bc040000 ti: fffffe03bc080000 task.ti: fffffe03bc080000 > PC is at __list_add+0x10/0xd4 > LR is at free_one_page+0x270/0x638 > ... > Call trace: > [<fffffe00003ee970>] __list_add+0x10/0xd4 > [<fffffe000019c478>] free_one_page+0x26c/0x638 > [<fffffe000019c8c8>] __free_pages_ok.part.52+0x84/0xbc > [<fffffe000019d5e8>] __free_pages+0x74/0xbc > [<fffffe0000c01350>] init_cma_reserved_pageblock+0xe8/0x104 > [<fffffe0000c24de0>] cma_init_reserved_areas+0x190/0x1e4 > [<fffffe0000090418>] do_one_initcall+0xc4/0x154 > [<fffffe0000bf0a50>] kernel_init_freeable+0x204/0x2a8 > [<fffffe00007520a0>] kernel_init+0xc/0xd4 > > This happens because init_cma_reserved_pageblock() calls > __free_one_page() with pageblock_order as page order but it is bigger > han MAX_ORDER. This in turn causes accesses past zone->free_list[]. > > Fix the problem by changing init_cma_reserved_pageblock() such that it > splits pageblock into individual MAX_ORDER pages if pageblock is > bigger than a MAX_ORDER page. > > In cases where !CONFIG_HUGETLB_PAGE_SIZE_VARIABLE, which is all > architectures expect for ia64, powerpc and tile at the moment, the > “pageblock_order > MAX_ORDER” condition will be optimised out since > both sides of the operator are constants. In cases where pageblock > size is variable, the performance degradation should not be > significant anyway since init_cma_reserved_pageblock() is called > only at boot time at most MAX_CMA_AREAS times which by default is > eight. > > Cc: stable@vger.kernel.org > Signed-off-by: Michal Nazarewicz <mina86@mina86.com> > Reported-by: Mark Salter <msalter@redhat.com> > Tested-by: Christopher Covington <cov@codeaurora.org> > --- > mm/page_alloc.c | 16 ++++++++++++++-- > 1 file changed, 14 insertions(+), 2 deletions(-) > > Mark Salter wrote: > > I ended up needing this (on top of your patch) to get the system to > > boot. Each MAX_ORDER-1 group needs the refcount and migratetype set > > so that __free_pages does the right thing. > > > > diff --git a/mm/page_alloc.c b/mm/page_alloc.c > > index 02fb1ed..a7ca6cc 100644 > > --- a/mm/page_alloc.c > > +++ b/mm/page_alloc.c > > @@ -799,17 +799,18 @@ void __init init_cma_reserved_pageblock(struct page *page) > > set_page_count(p, 0); > > } while (++p, --i); > > > > - set_page_refcounted(page); > > - set_pageblock_migratetype(page, MIGRATE_CMA); > > - > > - if (pageblock_order > MAX_ORDER) { > > - i = pageblock_order - MAX_ORDER; > > + if (pageblock_order >= MAX_ORDER) { > > + i = pageblock_order - MAX_ORDER + 1; > > i = 1 << i; > > p = page; > > do { > > - __free_pages(p, MAX_ORDER); > > + set_page_refcounted(p); > > + set_pageblock_migratetype(p, MIGRATE_CMA); > > + __free_pages(p, MAX_ORDER - 1); > > } while (p += MAX_ORDER_NR_PAGES, --i); > > } else { > > + set_page_refcounted(page); > > + set_pageblock_migratetype(page, MIGRATE_CMA); > > __free_pages(page, pageblock_order); > > } > > This is kinda embarrassing, dunno how I missed that. > > But each page actually does not need to have migratetype set, does it? > All of those pages are in a single pageblock so a single call > suffices. If you track set_pageblock_migratetype down to pfn_to_bitidx > there is: > > return (pfn >> pageblock_order) * NR_PAGEBLOCK_BITS; > > so for pfns inside of a pageblock, they get truncated. Or did I miss > yet another thing? Nope, my turn to miss something. You only need to set migrate type once per pageblock. > > diff --git a/mm/page_alloc.c b/mm/page_alloc.c > index ee92384..fef9614 100644 > --- a/mm/page_alloc.c > +++ b/mm/page_alloc.c > @@ -816,9 +816,21 @@ void __init init_cma_reserved_pageblock(struct page *page) > set_page_count(p, 0); > } while (++p, --i); > > - set_page_refcounted(page); > set_pageblock_migratetype(page, MIGRATE_CMA); > - __free_pages(page, pageblock_order); > + > + if (pageblock_order >= MAX_ORDER) { > + i = pageblock_nr_pages; > + p = page; > + do { > + set_page_refcounted(p); > + __free_pages(p, MAX_ORDER - 1); > + p += MAX_ORDER_NR_PAGES; > + } while (i -= MAX_ORDER_NR_PAGES); > + } else { > + set_page_refcounted(page); > + __free_pages(page, pageblock_order); > + } > + > adjust_managed_page_count(page, pageblock_nr_pages); > } > #endif This version works for me. Thanks.
diff --git a/mm/page_alloc.c b/mm/page_alloc.c index ee92384..fef9614 100644 --- a/mm/page_alloc.c +++ b/mm/page_alloc.c @@ -816,9 +816,21 @@ void __init init_cma_reserved_pageblock(struct page *page) set_page_count(p, 0); } while (++p, --i); - set_page_refcounted(page); set_pageblock_migratetype(page, MIGRATE_CMA); - __free_pages(page, pageblock_order); + + if (pageblock_order >= MAX_ORDER) { + i = pageblock_nr_pages; + p = page; + do { + set_page_refcounted(p); + __free_pages(p, MAX_ORDER - 1); + p += MAX_ORDER_NR_PAGES; + } while (i -= MAX_ORDER_NR_PAGES); + } else { + set_page_refcounted(page); + __free_pages(page, pageblock_order); + } + adjust_managed_page_count(page, pageblock_nr_pages); } #endif