On 18.07.24 05:04, Miaohe Lin wrote:
On 2024/7/17 17:01, David Hildenbrand wrote:
On 16.07.24 04:34, Miaohe Lin wrote:
On 2024/7/16 0:16, David Hildenbrand wrote:
On 15.07.24 08:23, Miaohe Lin wrote:
On 2024/7/13 5:09, Andrew Morton wrote:
On Fri, 12 Jul 2024 14:42:49 +0800 Miaohe Lin <linmiaohe@xxxxxxxxxx> wrote:
When I did memory failure tests recently, below panic occurs:
page dumped because: VM_BUG_ON_PAGE(PagePoisoned(page))
kernel BUG at include/linux/page-flags.h:616!
Oops: invalid opcode: 0000 [#1] PREEMPT SMP NOPTI
CPU: 3 PID: 720 Comm: bash Not tainted 6.10.0-rc1-00195-g148743902568 #40
RIP: 0010:unpoison_memory+0x2f3/0x590
RSP: 0018:ffffa57fc8787d60 EFLAGS: 00000246
RAX: 0000000000000037 RBX: 0000000000000009 RCX: ffff9be25fcdc9c8
RDX: 0000000000000000 RSI: 0000000000000027 RDI: ffff9be25fcdc9c0
RBP: 0000000000300000 R08: ffffffffb4956f88 R09: 0000000000009ffb
R10: 0000000000000284 R11: ffffffffb4926fa0 R12: ffffe6b00c000000
R13: ffff9bdb453dfd00 R14: 0000000000000000 R15: fffffffffffffffe
FS: 00007f08f04e4740(0000) GS:ffff9be25fcc0000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000564787a30410 CR3: 000000010d4e2000 CR4: 00000000000006f0
Call Trace:
<TASK>
unpoison_memory+0x2f3/0x590
simple_attr_write_xsigned.constprop.0.isra.0+0xb3/0x110
debugfs_attr_write+0x42/0x60
full_proxy_write+0x5b/0x80
vfs_write+0xd5/0x540
ksys_write+0x64/0xe0
do_syscall_64+0xb9/0x1d0
entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7f08f0314887
RSP: 002b:00007ffece710078 EFLAGS: 00000246 ORIG_RAX: 0000000000000001
RAX: ffffffffffffffda RBX: 0000000000000009 RCX: 00007f08f0314887
RDX: 0000000000000009 RSI: 0000564787a30410 RDI: 0000000000000001
RBP: 0000564787a30410 R08: 000000000000fefe R09: 000000007fffffff
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000009
R13: 00007f08f041b780 R14: 00007f08f0417600 R15: 00007f08f0416a00
</TASK>
Modules linked in: hwpoison_inject
---[ end trace 0000000000000000 ]---
RIP: 0010:unpoison_memory+0x2f3/0x590
RSP: 0018:ffffa57fc8787d60 EFLAGS: 00000246
RAX: 0000000000000037 RBX: 0000000000000009 RCX: ffff9be25fcdc9c8
RDX: 0000000000000000 RSI: 0000000000000027 RDI: ffff9be25fcdc9c0
RBP: 0000000000300000 R08: ffffffffb4956f88 R09: 0000000000009ffb
R10: 0000000000000284 R11: ffffffffb4926fa0 R12: ffffe6b00c000000
R13: ffff9bdb453dfd00 R14: 0000000000000000 R15: fffffffffffffffe
FS: 00007f08f04e4740(0000) GS:ffff9be25fcc0000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000564787a30410 CR3: 000000010d4e2000 CR4: 00000000000006f0
Kernel panic - not syncing: Fatal exception
Kernel Offset: 0x31c00000 from 0xffffffff81000000 (relocation range: 0xffffffff80000000-0xffffffffbfffffff)
---[ end Kernel panic - not syncing: Fatal exception ]---
The root cause is that unpoison_memory() tries to check the PG_HWPoison
flags of an uninitialized page. So VM_BUG_ON_PAGE(PagePoisoned(page)) is
triggered.
I'm not seeing the call path. Is this BUG happening via
static __always_inline void __ClearPage##uname(struct page *page) \
{ \
VM_BUG_ON_PAGE(!Page##uname(page), page); \
page->page_type |= PG_##lname; \
}
?
If so, where's the callsite?
It is BUG on PF_ANY():
PAGEFLAG(HWPoison, hwpoison, PF_ANY)
#define PF_ANY(page, enforce) PF_POISONED_CHECK(page)
#define PF_POISONED_CHECK(page) ({ \
VM_BUG_ON_PGFLAGS(PagePoisoned(page), page); \
page; })
#define PAGE_POISON_PATTERN -1l
static inline int PagePoisoned(const struct page *page)
{
return READ_ONCE(page->flags) == PAGE_POISON_PATTERN;
}
The offlined pages will have page->flags set to PAGE_POISON_PATTERN while pfn is still valid:
offline_pages
remove_pfn_range_from_zone
page_init_poison
memset(page, PAGE_POISON_PATTERN, size);
Worth noting that this happens after __offline_isolated_pages() marked the covering sections as offline.
Are we missing a pfn_to_online_page() check somewhere, or are we racing with offlining code that marks the section offline?
I was thinking about to use pfn_to_online_page() instead of pfn_to_page() in unpoison_memory() so we can get rid of offlined pages.
But there're ZONE_DEVICE pages. They're not-onlined too. And unpoison_memory() should work for them. So we can't simply use
pfn_to_online_page() in that. Or am I miss something?
Right, pfn_to_online_page() does not detect ZONE_DEVICE. That has to be handled separately if pfn_to_online_page() would fail.
... which is what we do in memory_failure():
p = pfn_to_online_page(pfn);
if (!p) {
if (pfn_valid(pfn)) {
pgmap = get_dev_pagemap(pfn, NULL);
put_ref_page(pfn, flags);
if (pgmap) {
...
}
}
...
}
Yup, this will be a good alternative. But will it be better to simply check PagePoisoned() instead?
The memmap of offline memory sections shall not be touched, so ....
don't touch it ;)
Especially because that PagePoisoned() check is non-sensical without
poisoining-during-memmap-init. You would still work with memory in
offline sections.
I think the code is even wrong in that regard: we allow for memory
offlining to work with HWPoisoned pages, see __offline_isolated_pages().
Staring at unpoison_memory(), we might be putting these pages back to
the buddy? Which is completely wrong.
... not to mention that a function called "unpoison_memory()" doing
nothing when it finds PagePoison() is completely confusing. Last but not
least, take a look at the number of users of PagePoison().
Likely PagePoison() warrants a cleanup, but I am not sure yet what's the
right thing to do.
--
Cheers,
David / dhildenb
