On 15.05.24 04:36, Miaohe Lin wrote:
> When I did memory failure tests recently, below panic occurs:
>
> kernel BUG at include/linux/mm.h:1135!
> invalid opcode: 0000 [#1] PREEMPT SMP NOPTI
> CPU: 9 PID: 137 Comm: kswapd1 Not tainted 6.9.0-rc4-00491-gd5ce28f156fe-dirty #14
> RIP: 0010:shrink_huge_zero_page_scan+0x168/0x1a0
> RSP: 0018:ffff9933c6c57bd0 EFLAGS: 00000246
> RAX: 000000000000003e RBX: 0000000000000000 RCX: ffff88f61fc5c9c8
> RDX: 0000000000000000 RSI: 0000000000000027 RDI: ffff88f61fc5c9c0
> RBP: ffffcd7c446b0000 R08: ffffffff9a9405f0 R09: 0000000000005492
> R10: 00000000000030ea R11: ffffffff9a9405f0 R12: 0000000000000000
> R13: 0000000000000000 R14: 0000000000000000 R15: ffff88e703c4ac00
> FS: 0000000000000000(0000) GS:ffff88f61fc40000(0000) knlGS:0000000000000000
> CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
> CR2: 000055f4da6e9878 CR3: 0000000c71048000 CR4: 00000000000006f0
> Call Trace:
> <TASK>
> do_shrink_slab+0x14f/0x6a0
> shrink_slab+0xca/0x8c0
> shrink_node+0x2d0/0x7d0
> balance_pgdat+0x33a/0x720
> kswapd+0x1f3/0x410
> kthread+0xd5/0x100
> ret_from_fork+0x2f/0x50
> ret_from_fork_asm+0x1a/0x30
> </TASK>
> Modules linked in: mce_inject hwpoison_inject
> ---[ end trace 0000000000000000 ]---
> RIP: 0010:shrink_huge_zero_page_scan+0x168/0x1a0
> RSP: 0018:ffff9933c6c57bd0 EFLAGS: 00000246
> RAX: 000000000000003e RBX: 0000000000000000 RCX: ffff88f61fc5c9c8
> RDX: 0000000000000000 RSI: 0000000000000027 RDI: ffff88f61fc5c9c0
> RBP: ffffcd7c446b0000 R08: ffffffff9a9405f0 R09: 0000000000005492
> R10: 00000000000030ea R11: ffffffff9a9405f0 R12: 0000000000000000
> R13: 0000000000000000 R14: 0000000000000000 R15: ffff88e703c4ac00
> FS: 0000000000000000(0000) GS:ffff88f61fc40000(0000) knlGS:0000000000000000
> CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
> CR2: 000055f4da6e9878 CR3: 0000000c71048000 CR4: 00000000000006f0
>
> The root cause is that HWPoison flag will be set for huge_zero_folio
> without increasing the folio refcnt. But then unpoison_memory() will
> decrease the folio refcnt unexpectly as it appears like a successfully
> hwpoisoned folio leading to VM_BUG_ON_PAGE(page_ref_count(page) == 0)
> when releasing huge_zero_folio.
>
> Skip unpoisoning huge_zero_folio in unpoison_memory() to fix this issue.
> We're not prepared to unpoison huge_zero_folio yet.
>
> Fixes: 478d134e9506 ("mm/huge_memory: do not overkill when splitting huge_zero_page")
> Signed-off-by: Miaohe Lin <[email protected]>
> Cc: <[email protected]>
> ---
> v2:
> Change to simply check for the huge zero page. Thanks.
> ---
> mm/memory-failure.c | 6 ++++++
> 1 file changed, 6 insertions(+)
>
> diff --git a/mm/memory-failure.c b/mm/memory-failure.c
> index 16ada4fb02b7..68bc8d7ff53d 100644
> --- a/mm/memory-failure.c
> +++ b/mm/memory-failure.c
> @@ -2558,6 +2558,12 @@ int unpoison_memory(unsigned long pfn)
> goto unlock_mutex;
> }
>
> + if (is_huge_zero_folio(folio)) {
> + unpoison_pr_info("Unpoison: huge zero page is not supported %#lx\n",
> + pfn, &unpoison_rs);
> + goto unlock_mutex;
> + }
> +
> if (folio_test_slab(folio) || folio_test_pgtable(folio) ||
> folio_test_reserved(folio) || folio_test_offline(folio))
> goto unlock_mutex;
Acked-by: David Hildenbrand <[email protected]>
--
Cheers,
David / dhildenb
On Wed, May 15, 2024 at 05:55:39PM +0200, David Hildenbrand wrote:
> > + if (is_huge_zero_folio(folio)) {
> > + unpoison_pr_info("Unpoison: huge zero page is not supported %#lx\n",
> > + pfn, &unpoison_rs);
> > + goto unlock_mutex;
> > + }
> > +
Sorry for spamming your reply David, but for some unknown reason I am not able
to find the original patch in my mailbox, in none of the two accountes I am
subscribed, so I guess I will have to reply here.
Just two things
1) We do not care if someone grabs a refcount for huge_zero_folio,
because since it is not supported anyway the outcome will not change.
Also, AFAIK, there is no chance we can unpoison that folio.
Therefore, I would just lift the check two blocks and place it right after
the hw_memory_failure check.
2) The whole thing is unsupported, but you will return -EBUSY while you
should be returning -EOPNOTSUPP AFAICS.
with that you can add:
Reviewed-by: Oscar Salvador <[email protected]>
--
Oscar Salvador
SUSE Labs