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 6459c73c4e2a6313f71761f1a55034d9d1e20f37..0c1ab7f7c102ede78d0b445dbc527e28b78bd5a7 100644 (file)
--- a/mm/huge_memory.c
+++ b/mm/huge_memory.c
@@ -2674,9 +2674,10 @@ 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;