Re: [PATCH 03/16] page-flags: introduce page flags policies wrt compound pages
From: Konstantin Khlebnikov
Date: Fri Sep 25 2015 - 08:29:54 EST
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@xxxxxxxxxxxxxxx>
---
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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