| Message ID | xa1td2e41xs2.fsf@mina86.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
On 06/19/2014 03:53 PM, 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 I just ran into this. Thanks for the fix. Tested-by: Christopher Covington <cov@codeaurora.org>
On Thu, 2014-06-19 at 21:53 +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. > > Signed-off-by: Michal Nazarewicz <mina86@mina86.com> > Reported-by: Mark Salter <msalter@redhat.com> > --- > mm/page_alloc.c | 13 ++++++++++++- > 1 file changed, 12 insertions(+), 1 deletion(-) > > diff --git a/mm/page_alloc.c b/mm/page_alloc.c > index 7f97767..fe114db 100644 > --- a/mm/page_alloc.c > +++ b/mm/page_alloc.c > @@ -817,7 +817,18 @@ void __init init_cma_reserved_pageblock(struct page *page) > > set_page_refcounted(page); > set_pageblock_migratetype(page, MIGRATE_CMA); > - __free_pages(page, pageblock_order); > + > + if (pageblock_order > MAX_ORDER) { > + i = pageblock_order - MAX_ORDER; > + i = 1 << i; > + p = page; > + do { > + __free_pages(p, MAX_ORDER); > + } while (p += MAX_ORDER_NR_PAGES, --i); > + } else { > + __free_pages(page, pageblock_order); > + } > + > adjust_managed_page_count(page, pageblock_nr_pages); > } > #endif This still isn't quite right. __free_pages can only take up to MAX_ORDER-1 (MAX_ORDER_NR_PAGES is 1 << (MAX_ORDER - 1)). But I'm hitting a slightly different issue even with that fixed up. Still looking...
On Fri, Jun 20 2014, Mark Salter <msalter@redhat.com> wrote: > This still isn't quite right. __free_pages can only take up to > MAX_ORDER-1 (MAX_ORDER_NR_PAGES is 1 << (MAX_ORDER - 1)). Good catch. I'll send v3 in a few days then.
diff --git a/mm/page_alloc.c b/mm/page_alloc.c index 7f97767..fe114db 100644 --- a/mm/page_alloc.c +++ b/mm/page_alloc.c @@ -817,7 +817,18 @@ void __init init_cma_reserved_pageblock(struct page *page) set_page_refcounted(page); set_pageblock_migratetype(page, MIGRATE_CMA); - __free_pages(page, pageblock_order); + + if (pageblock_order > MAX_ORDER) { + i = pageblock_order - MAX_ORDER; + i = 1 << i; + p = page; + do { + __free_pages(p, MAX_ORDER); + } while (p += MAX_ORDER_NR_PAGES, --i); + } else { + __free_pages(page, pageblock_order); + } + adjust_managed_page_count(page, pageblock_nr_pages); } #endif
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. Signed-off-by: Michal Nazarewicz <mina86@mina86.com> Reported-by: Mark Salter <msalter@redhat.com> --- mm/page_alloc.c | 13 ++++++++++++- 1 file changed, 12 insertions(+), 1 deletion(-)