From patchwork Mon Aug 31 01:30:21 2020 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Andrew Morton X-Patchwork-Id: 264844 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-7.0 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED, DKIM_VALID, HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI, SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED autolearn=no autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 56519C433E7 for ; Mon, 31 Aug 2020 01:30:41 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 36F612076D for ; Mon, 31 Aug 2020 01:30:41 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1598837441; bh=7+p+Io5ZRf+HW37PZfH3O30h9pXNKs7fjQxr0jbf/xc=; h=Date:From:To:Subject:List-ID:From; b=qcAZ1RKqcuoaLJxxp+T5bB6iUMTEwfSHHL1jFXIp0QLmalpI2rTBjmCufIxhd4xNM frfmP49g33r0ooeQpTqwBEJWwjSHpf68mVJOPJy8j7AFu50V8M4AzRYvanITnZEt8M y5bzOeALM4PXH0+DnO5T8PpGjUt+/g9nSNo2Wj1c= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727813AbgHaBaj (ORCPT ); Sun, 30 Aug 2020 21:30:39 -0400 Received: from mail.kernel.org ([198.145.29.99]:56434 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727784AbgHaBaW (ORCPT ); Sun, 30 Aug 2020 21:30:22 -0400 Received: from X1 (unknown [65.49.58.28]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id 05A612076D; Mon, 31 Aug 2020 01:30:21 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1598837422; bh=7+p+Io5ZRf+HW37PZfH3O30h9pXNKs7fjQxr0jbf/xc=; h=Date:From:To:Subject:From; b=tvVCNSVDSpb2CHCkb2uwgzPc0+yNDp6N8J7z+6OlmKAIfGrNXSr60/2DtNWoh8zDY fZVwTXf7VbmRyV+k1q0STuOPeupTnkPOW+WIx5Q2pBEdwjY45eKEA2LjOFLwNdVbDg dcKMgzjnVokVpToswY8AzIPOGynnx3zeJmKw3Mcg= Date: Sun, 30 Aug 2020 18:30:21 -0700 From: akpm@linux-foundation.org To: mm-commits@vger.kernel.org, stable@vger.kernel.org, shakeelb@google.com, mike.kravetz@oracle.com, mhocko@suse.com, hannes@cmpxchg.org, cai@lca.pw, alex.shi@linux.alibaba.com, hughd@google.com Subject: + shmem-shmem_writepage-split-unlikely-i915-thp.patch added to -mm tree Message-ID: <20200831013021.iDuAW%akpm@linux-foundation.org> User-Agent: s-nail v14.9.10 Sender: stable-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: stable@vger.kernel.org The patch titled Subject: shmem: shmem_writepage() split unlikely i915 THP has been added to the -mm tree. Its filename is shmem-shmem_writepage-split-unlikely-i915-thp.patch This patch should soon appear at http://ozlabs.org/~akpm/mmots/broken-out/shmem-shmem_writepage-split-unlikely-i915-thp.patch and later at http://ozlabs.org/~akpm/mmotm/broken-out/shmem-shmem_writepage-split-unlikely-i915-thp.patch Before you just go and hit "reply", please: a) Consider who else should be cc'ed b) Prefer to cc a suitable mailing list as well c) Ideally: find the original patch on the mailing list and do a reply-to-all to that, adding suitable additional cc's *** Remember to use Documentation/process/submit-checklist.rst when testing your code *** The -mm tree is included into linux-next and is updated there every 3-4 working days ------------------------------------------------------ From: Hugh Dickins Subject: shmem: shmem_writepage() split unlikely i915 THP drivers/gpu/drm/i915/gem/i915_gem_shmem.c contains a shmem_writeback() which calls shmem_writepage() from a shrinker: that usually works well enough; but if /sys/kernel/mm/transparent_hugepage/shmem_enabled has been set to "force" (documented as "Force the huge option on for all - very useful for testing"), shmem_writepage() is surprised to be called with a huge page, and crashes on the VM_BUG_ON_PAGE(PageCompound) (I did not find out where the crash happens when CONFIG_DEBUG_VM is off). LRU page reclaim always splits the shmem huge page first: I'd prefer not to demand that of i915, so check and split compound in shmem_writepage(). Link: http://lkml.kernel.org/r/alpine.LSU.2.11.2008301401390.5954@eggly.anvils Fixes: 2d6692e642e7 ("drm/i915: Start writeback from the shrinker") Signed-off-by: Hugh Dickins Cc: Alex Shi Cc: Johannes Weiner Cc: Michal Hocko Cc: Mike Kravetz Cc: Qian Cai Cc: Shakeel Butt Cc: [5.3+] Signed-off-by: Andrew Morton --- mm/shmem.c | 10 +++++++++- 1 file changed, 9 insertions(+), 1 deletion(-) --- a/mm/shmem.c~shmem-shmem_writepage-split-unlikely-i915-thp +++ a/mm/shmem.c @@ -1362,7 +1362,15 @@ static int shmem_writepage(struct page * swp_entry_t swap; pgoff_t index; - VM_BUG_ON_PAGE(PageCompound(page), page); + /* + * If /sys/kernel/mm/transparent_hugepage/shmem_enabled is "force", + * then drivers/gpu/drm/i915/gem/i915_gem_shmem.c gets huge pages, + * and its shmem_writeback() needs them to be split when swapping. + */ + if (PageTransCompound(page)) + if (split_huge_page(page) < 0) + goto redirty; + BUG_ON(!PageLocked(page)); mapping = page->mapping; index = page->index;