The patch titled Subject: mm/huge_memory.c: warn with pr_warn_ratelimited instead of VM_WARN_ON_ONCE_FOLIO has been added to the -mm mm-hotfixes-unstable branch. Its filename is mm-huge_memoryc-warn-with-pr_warn_ratelimited-instead-of-vm_warn_on_once_folio.patch

This patch will shortly appear at https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches...

This patch will later appear in the mm-hotfixes-unstable branch at git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm

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------------------------------------------------------ From: Naoya Horiguchi naoya.horiguchi@nec.com Subject: mm/huge_memory.c: warn with pr_warn_ratelimited instead of VM_WARN_ON_ONCE_FOLIO Date: Thu, 6 Apr 2023 17:20:04 +0900

split_huge_page_to_list() WARNs when called for huge zero pages, which sounds to me too harsh because it does not imply a kernel bug, but just notifies the event to admins. On the other hand, this is considered as critical by syzkaller and makes its testing less efficient, which seems to me harmful.

So replace the VM_WARN_ON_ONCE_FOLIO with pr_warn_ratelimited.

Link: https://lkml.kernel.org/r/20230406082004.2185420-1-naoya.horiguchi@linux.dev Fixes: 478d134e9506 ("mm/huge_memory: do not overkill when splitting huge_zero_page") Signed-off-by: Naoya Horiguchi naoya.horiguchi@nec.com Reported-by: syzbot+07a218429c8d19b1fb25@syzkaller.appspotmail.com Link: https://lore.kernel.org/lkml/000000000000a6f34a05e6efcd01@google.com/ Cc: Miaohe Lin linmiaohe@huawei.com Cc: Tetsuo Handa penguin-kernel@i-love.sakura.ne.jp Cc: Xu Yu xuyu@linux.alibaba.com Cc: Yang Shi shy828301@gmail.com Cc: stable@vger.kernel.org Signed-off-by: Andrew Morton akpm@linux-foundation.org ---

mm/huge_memory.c | 5 +++-- 1 file changed, 3 insertions(+), 2 deletions(-)

--- a/mm/huge_memory.c~mm-huge_memoryc-warn-with-pr_warn_ratelimited-instead-of-vm_warn_on_once_folio +++ a/mm/huge_memory.c @@ -2665,9 +2665,10 @@ int split_huge_page_to_list(struct page VM_BUG_ON_FOLIO(!folio_test_large(folio), folio);

is_hzp = is_huge_zero_page(&folio->page); - VM_WARN_ON_ONCE_FOLIO(is_hzp, folio); - if (is_hzp) + if (is_hzp) { + pr_warn_ratelimited("Called split_huge_page for huge zero page\n"); return -EBUSY; + }

if (folio_test_writeback(folio)) return -EBUSY; _

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

mm-huge_memoryc-warn-with-pr_warn_ratelimited-instead-of-vm_warn_on_once_folio.patch