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SubjectRe: [PATCH 03/16] page-flags: introduce page flags policies wrt compound pages
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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@linux.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

[ 0.000000] Policy zone: DMA32
[ 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 ]---


> + page;})
> +



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