The patch titled Subject: mm/hwpoison: use pr_err() instead of dump_page() in get_any_page() has been added to the -mm tree. Its filename is mm-hwpoison-use-pr_err-instead-of-dump_page-in-get_any_page.patch

This patch should soon appear at https://ozlabs.org/~akpm/mmots/broken-out/mm-hwpoison-use-pr_err-instead-of-... and later at https://ozlabs.org/~akpm/mmotm/broken-out/mm-hwpoison-use-pr_err-instead-of-...

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------------------------------------------------------ From: Naoya Horiguchi naoya.horiguchi@nec.com Subject: mm/hwpoison: use pr_err() instead of dump_page() in get_any_page()

The following VM_BUG_ON_FOLIO() is triggered when memory error event happens on the (thp/folio) pages which are about to be freed:

[ 1160.232771] page:00000000b36a8a0f refcount:1 mapcount:0 mapping:0000000000000000 index:0x1 pfn:0x16a000 [ 1160.236916] page:00000000b36a8a0f refcount:0 mapcount:0 mapping:0000000000000000 index:0x1 pfn:0x16a000 [ 1160.240684] flags: 0x57ffffc0800000(hwpoison|node=1|zone=2|lastcpupid=0x1fffff) [ 1160.243458] raw: 0057ffffc0800000 dead000000000100 dead000000000122 0000000000000000 [ 1160.246268] raw: 0000000000000001 0000000000000000 00000000ffffffff 0000000000000000 [ 1160.249197] page dumped because: VM_BUG_ON_FOLIO(!folio_test_large(folio)) [ 1160.251815] ------------[ cut here ]------------ [ 1160.253438] kernel BUG at include/linux/mm.h:788! [ 1160.256162] invalid opcode: 0000 [#1] PREEMPT SMP PTI [ 1160.258172] CPU: 2 PID: 115368 Comm: mceinj.sh Tainted: G E 5.18.0-rc1-v5.18-rc1-220404-2353-005-g83111+ #3 [ 1160.262049] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.15.0-1.fc35 04/01/2014 [ 1160.265103] RIP: 0010:dump_page.cold+0x27e/0x2bd [ 1160.266757] Code: fe ff ff 48 c7 c6 81 f1 5a 98 e9 4c fe ff ff 48 c7 c6 a1 95 59 98 e9 40 fe ff ff 48 c7 c6 50 bf 5a 98 48 89 ef e8 9d 04 6d ff <0f> 0b 41 f7 c4 ff 0f 00 00 0f 85 9f fd ff ff 49 8b 04 24 a9 00 00 [ 1160.273180] RSP: 0018:ffffaa2c4d59fd18 EFLAGS: 00010292 [ 1160.274969] RAX: 000000000000003e RBX: 0000000000000001 RCX: 0000000000000000 [ 1160.277263] RDX: 0000000000000001 RSI: ffffffff985995a1 RDI: 00000000ffffffff [ 1160.279571] RBP: ffffdc9c45a80000 R08: 0000000000000000 R09: 00000000ffffdfff [ 1160.281794] R10: ffffaa2c4d59fb08 R11: ffffffff98940d08 R12: ffffdc9c45a80000 [ 1160.283920] R13: ffffffff985b6f94 R14: 0000000000000000 R15: ffffdc9c45a80000 [ 1160.286641] FS: 00007eff54ce1740(0000) GS:ffff99c67bd00000(0000) knlGS:0000000000000000 [ 1160.289498] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 [ 1160.291106] CR2: 00005628381a5f68 CR3: 0000000104712003 CR4: 0000000000170ee0 [ 1160.293031] Call Trace: [ 1160.293724] <TASK> [ 1160.294334] get_hwpoison_page+0x47d/0x570 [ 1160.295474] memory_failure+0x106/0xaa0 [ 1160.296474] ? security_capable+0x36/0x50 [ 1160.297524] hard_offline_page_store+0x43/0x80 [ 1160.298684] kernfs_fop_write_iter+0x11c/0x1b0 [ 1160.299829] new_sync_write+0xf9/0x160 [ 1160.300810] vfs_write+0x209/0x290 [ 1160.301835] ksys_write+0x4f/0xc0 [ 1160.302718] do_syscall_64+0x3b/0x90 [ 1160.303664] entry_SYSCALL_64_after_hwframe+0x44/0xae [ 1160.304981] RIP: 0033:0x7eff54b018b7

As shown in the RIP address, this VM_BUG_ON in folio_entire_mapcount() is called from dump_page("hwpoison: unhandlable page") in get_any_page(). The below explains the mechanism of the race:

CPU 0 CPU 1

memory_failure get_hwpoison_page get_any_page dump_page compound = PageCompound free_pages_prepare page->flags &= ~PAGE_FLAGS_CHECK_AT_PREP folio_entire_mapcount VM_BUG_ON_FOLIO(!folio_test_large(folio))

So replace dump_page() with safer one, pr_err().

Link: https://lkml.kernel.org/r/20220427053220.719866-1-naoya.horiguchi@linux.dev Fixes: 74e8ee4708a8 ("mm: Turn head_compound_mapcount() into folio_entire_mapcount()") Signed-off-by: Naoya Horiguchi naoya.horiguchi@nec.com Cc: Matthew Wilcox willy@infradead.org Cc: Miaohe Lin linmiaohe@huawei.com Cc: Christoph Hellwig hch@infradead.org Cc: John Hubbard jhubbard@nvidia.com Cc: Jason Gunthorpe jgg@nvidia.com Cc: William Kucharski william.kucharski@oracle.com Cc: stable@vger.kernel.org Signed-off-by: Andrew Morton akpm@linux-foundation.org ---

mm/memory-failure.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)

--- a/mm/memory-failure.c~mm-hwpoison-use-pr_err-instead-of-dump_page-in-get_any_page +++ a/mm/memory-failure.c @@ -1274,7 +1274,7 @@ try_again: } out: if (ret == -EIO) - dump_page(p, "hwpoison: unhandlable page"); + pr_err("Memory failure: %#lx: unhandlable page.\n", page_to_pfn(p));

return ret; } _

Patches currently in -mm which might be from naoya.horiguchi@nec.com are

mm-hwpoison-use-pr_err-instead-of-dump_page-in-get_any_page.patch mm-hwpoison-put-page-in-already-hwpoisoned-case-with-mf_count_increased.patch revert-mm-memory-failurec-fix-race-with-changing-page-compound-again.patch mm-hugetlb-hwpoison-separate-branch-for-free-and-in-use-hugepage.patch