On Thu, 15 Jan 2026 08:13:43 +0800 [off-list ref] wrote:

From: "robin.kuo" <redacted>

Restore swap_space attr avoid krn panic

Thanks, and welcome to Linux ;)

Commit 8b47299a411a ('mm, swap: mark swap address space ro and add
context debug check') made the swap address space read-only.
It may lead to kernel panic if arch_prepare_to_swap returns a failure 
under heavy memory pressure as follows,

el1_abort+0x40/0x64
el1h_64_sync_handler+0x48/0xcc
el1h_64_sync+0x84/0x88
errseq_set+0x4c/0xb8 (P)
__filemap_set_wb_err+0x20/0xd0
shrink_folio_list+0xc20/0x11cc
evict_folios+0x1520/0x1be4
try_to_shrink_lruvec+0x27c/0x3dc
shrink_one+0x9c/0x228
shrink_node+0xb3c/0xeac
do_try_to_free_pages+0x170/0x4f0
try_to_free_pages+0x334/0x534
__alloc_pages_direct_reclaim+0x90/0x158
__alloc_pages_slowpath+0x334/0x588
__alloc_frozen_pages_noprof+0x224/0x2fc
__folio_alloc_noprof+0x14/0x64
vma_alloc_zeroed_movable_folio+0x34/0x44
do_pte_missing+0xad4/0x1040
handle_mm_fault+0x4a4/0x790
do_page_fault+0x288/0x5f8
do_translation_fault+0x38/0x54
do_mem_abort+0x54/0xa8

Restore swap address space as not ro to avoid the panic.

Well damn.  We have checking tools which should be able to detect this:
we referenced something which was dropped from kernel memory in the
calling function's context.  i don't know who I should report this to.

I shall add cc:stable to this patch, to help ensure that it is
backported into 6.18.x.