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Date: Mon, 28 Sep 2015 13:02:19 +0300
From: Konstantin Khlebnikov <khlebnikov@...dex-team.ru>
To: "Kirill A. Shutemov" <kirill@...temov.name>
Cc: "Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>,
Andrew Morton <akpm@...ux-foundation.org>,
Andrea Arcangeli <aarcange@...hat.com>,
Hugh Dickins <hughd@...gle.com>,
Dave Hansen <dave.hansen@...el.com>,
Mel Gorman <mgorman@...e.de>, Rik van Riel <riel@...hat.com>,
Vlastimil Babka <vbabka@...e.cz>,
Christoph Lameter <cl@...two.org>,
Naoya Horiguchi <n-horiguchi@...jp.nec.com>,
Steve Capper <steve.capper@...aro.org>,
"Aneesh Kumar K.V" <aneesh.kumar@...ux.vnet.ibm.com>,
Johannes Weiner <hannes@...xchg.org>,
Michal Hocko <mhocko@...e.cz>,
Jerome Marchand <jmarchan@...hat.com>,
Sasha Levin <sasha.levin@...cle.com>,
linux-kernel@...r.kernel.org, linux-mm@...ck.org
Subject: Re: [PATCH 03/16] page-flags: introduce page flags policies wrt
compound pages
On 25.09.2015 22:13, Kirill A. Shutemov wrote:
> On Fri, Sep 25, 2015 at 03:29:17PM +0300, Konstantin Khlebnikov wrote:
>> On 24.09.2015 17:50, Kirill A. Shutemov wrote:
>>> This patch adds a third argument to macros which create function
>>> definitions for page flags. This argument defines how page-flags helpers
>>> behave on compound functions.
>>>
>>> For now we define four policies:
>>>
>>> - PF_ANY: the helper function operates on the page it gets, regardless
>>> if it's non-compound, head or tail.
>>>
>>> - PF_HEAD: the helper function operates on the head page of the compound
>>> page if it gets tail page.
>>>
>>> - PF_NO_TAIL: only head and non-compond pages are acceptable for this
>>> helper function.
>>>
>>> - PF_NO_COMPOUND: only non-compound pages are acceptable for this helper
>>> function.
>>>
>>> For now we use policy PF_ANY for all helpers, which matches current
>>> behaviour.
>>>
>>> We do not enforce the policy for TESTPAGEFLAG, because we have flags
>>> checked for random pages all over the kernel. Noticeable exception to
>>> this is PageTransHuge() which triggers VM_BUG_ON() for tail page.
>>>
>>> Signed-off-by: Kirill A. Shutemov <kirill.shutemov@...ux.intel.com>
>>> ---
>>> include/linux/page-flags.h | 154 ++++++++++++++++++++++++++-------------------
>>> 1 file changed, 90 insertions(+), 64 deletions(-)
>>>
>>> diff --git a/include/linux/page-flags.h b/include/linux/page-flags.h
>>> index 713d3f2c2468..1b3babe5ff69 100644
>>> --- a/include/linux/page-flags.h
>>> +++ b/include/linux/page-flags.h
>>> @@ -154,49 +154,68 @@ static inline int PageCompound(struct page *page)
>>> return test_bit(PG_head, &page->flags) || PageTail(page);
>>> }
>>>
>>> +/* Page flags policies wrt compound pages */
>>> +#define PF_ANY(page, enforce) page
>>> +#define PF_HEAD(page, enforce) compound_head(page)
>>> +#define PF_NO_TAIL(page, enforce) ({ \
>>> + if (enforce) \
>>> + VM_BUG_ON_PAGE(PageTail(page), page); \
>>> + else \
>>> + page = compound_head(page); \
>>> + page;})
>>> +#define PF_NO_COMPOUND(page, enforce) ({ \
>>> + if (enforce) \
>>> + VM_BUG_ON_PAGE(PageCompound(page), page); \
>>
>> Linux next-20150925 crashes here (at least in lkvm)
>> if CONFIG_DEFERRED_STRUCT_PAGE_INIT=y
>
> Hm. I don't see the crash in qemu. Could you share your config?
see in attachment
>
>> [ 0.000000] Kernel command line: noapic noacpi pci=conf1 reboot=k panic=1
>> i8042.direct=1 i8042.dumbkbd=1 i8042.nopnp=1 console=ttyS0
>> earlyprintk=serial i8042.noaux=1 root=/dev/root rw
>> rootflags=rw,trans=virtio,version=9p2000.L rootfstype=9p init=/virt/init
>> ip=dhcp
>> [ 0.000000] PID hash table entries: 2048 (order: 2, 16384 bytes)
>> [ 0.000000] BUG: unable to handle kernel NULL pointer dereference at
>> 000000000000000c
>> [ 0.000000] IP: [<ffffffff811aaafb>] dump_page_badflags+0x2b/0xe0
>> [ 0.000000] PGD 0
>> [ 0.000000] Oops: 0000 [#1] SMP
>> [ 0.000000] Modules linked in:
>> [ 0.000000] CPU: 0 PID: 0 Comm: swapper Not tainted
>> 4.3.0-rc2-next-20150925+ #2
>> [ 0.000000] task: ffffffff81c12580 ti: ffffffff81c00000 task.ti:
>> ffffffff81c00000
>> [ 0.000000] RIP: 0010:[<ffffffff811aaafb>] [<ffffffff811aaafb>]
>> dump_page_badflags+0x2b/0xe0
>> [ 0.000000] RSP: 0000:ffffffff81c03ea8 EFLAGS: 00010002
>> [ 0.000000] RAX: 000000000000000c RBX: ffffea00006dfd40 RCX:
>> 0000000000000100
>> [ 0.000000] RDX: 0000000000000001 RSI: ffffffff81a4aeb8 RDI:
>> ffffea00006dfd40
>> [ 0.000000] RBP: ffffffff81c03ec0 R08: 0000000000000000 R09:
>> 0000000000000000
>> [ 0.000000] R10: 0000000000000001 R11: 0000000000000000 R12:
>> 0000000000000000
>> [ 0.000000] R13: 000000000001b7f7 R14: ffffffff81fe50c0 R15:
>> ffffffff81c03fb0
>> [ 0.000000] FS: 0000000000000000(0000) GS:ffff88001a400000(0000)
>> knlGS:0000000000000000
>> [ 0.000000] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
>> [ 0.000000] CR2: 000000000000000c CR3: 0000000001c0b000 CR4:
>> 00000000000406b0
>> [ 0.000000] DR0: 0000000000000000 DR1: 0000000000000000 DR2:
>> 0000000000000000
>> [ 0.000000] DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7:
>> 0000000000000400
>> [ 0.000000] Stack:
>> [ 0.000000] 000000000001b7f5 ffffea00006dfd40 000000000001b7f7
>> ffffffff81c03ed0
>> [ 0.000000] ffffffff811aabc0 ffffffff81c03ef8 ffffffff81785eda
>> ffffffff81c03f10
>> [ 0.000000] 0000000000000040 ffffffff81fd99c0 ffffffff81c03f30
>> ffffffff81f66600
>> [ 0.000000] Call Trace:
>> [ 0.000000] [<ffffffff811aabc0>] dump_page+0x10/0x20
>> [ 0.000000] [<ffffffff81785eda>] reserve_bootmem_region+0xd9/0xe2
>> [ 0.000000] [<ffffffff81f66600>] free_all_bootmem+0x4b/0x11a
>> [ 0.000000] [<ffffffff81f5428d>] mem_init+0x6a/0x9d
>> [ 0.000000] [<ffffffff81f37d48>] start_kernel+0x214/0x46a
>> [ 0.000000] [<ffffffff81f37120>] ? early_idt_handler_array+0x120/0x120
>> [ 0.000000] [<ffffffff81f374d7>] x86_64_start_reservations+0x2a/0x2c
>> [ 0.000000] [<ffffffff81f3760f>] x86_64_start_kernel+0x136/0x145
>> [ 0.000000] Code: e8 3b 7b 5e 00 55 48 89 e5 41 55 41 54 49 89 d4 53 48
>> 8b 57 20 48 89 fb 4c 8b 4f 10 4c 8b 47 08 48 8d 42 ff 83 e2 01 48 0f 44 c7
>> <48> 8b 00 a8 80 75 4b 8b 4f 18 8b 57 1c 49 89 f5 31 c0 48 89 fe
>> [ 0.000000] RIP [<ffffffff811aaafb>] dump_page_badflags+0x2b/0xe0
>> [ 0.000000] RSP <ffffffff81c03ea8>
>> [ 0.000000] CR2: 000000000000000c
>> [ 0.000000] ---[ end trace cb88537fdc8fa200 ]---
>
> Could you try this:
>
> diff --git a/mm/page_alloc.c b/mm/page_alloc.c
> index 9bcfd70b1eb8..eff685f83879 100644
> --- a/mm/page_alloc.c
> +++ b/mm/page_alloc.c
> @@ -929,8 +929,6 @@ static void init_reserved_page(unsigned long pfn)
> #else
> static inline void init_reserved_page(unsigned long pfn)
> {
> - /* Avoid false-positive PageTail() */
> - INIT_LIST_HEAD(&pfn_to_page(pfn)->lru);
> }
> #endif /* CONFIG_DEFERRED_STRUCT_PAGE_INIT */
>
> @@ -950,6 +948,10 @@ void __meminit reserve_bootmem_region(unsigned long start, unsigned long end)
> struct page *page = pfn_to_page(start_pfn);
>
> init_reserved_page(start_pfn);
> +
> + /* Avoid false-positive PageTail() */
> + INIT_LIST_HEAD(&pfn_to_page(pfn)->lru);
> +
> SetPageReserved(page);
> }
> }
>
--
Konstantin
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