mm/huge_memory.c: warn with pr_warn_ratelimited instead of VM_WARN_ON_ONCE_FOLIO

commit 4737edbbdd4958ae29ca6a310a6a2fa4e0684b01 upstream.

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/
Reviewed-by: Yang Shi <shy828301@gmail.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: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/mm/huge_memory.c b/mm/huge_memory.c
index cfe8d77..b20fef2 100644 (file)
--- a/mm/huge_memory.c
+++ b/mm/huge_memory.c
@@ -2655,9 +2655,10 @@ int split_huge_page_to_list(struct page *page, struct list_head *list)
        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;