+ mm-huge_memoryc-warn-with-pr_warn_ratelimited-instead-of-vm_warn_on_once_folio.patch added to mm-hotfixes-unstable branch

+ mm-huge_memoryc-warn-with-pr_warn_ratelimited-instead-of-vm_warn_on_once_folio.patch added to mm-hotfixes-unstable branch

[Andrew Morton]

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

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