From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by smtp.lore.kernel.org (Postfix) with ESMTP id 3C3AFC4332F for ; Wed, 19 Oct 2022 18:42:18 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id CC63C6B0072; Wed, 19 Oct 2022 14:42:17 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id C76046B0073; Wed, 19 Oct 2022 14:42:17 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id B16C36B0074; Wed, 19 Oct 2022 14:42:17 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0013.hostedemail.com [216.40.44.13]) by kanga.kvack.org (Postfix) with ESMTP id 9EF456B0072 for ; Wed, 19 Oct 2022 14:42:17 -0400 (EDT) Received: from smtpin07.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay07.hostedemail.com (Postfix) with ESMTP id 5A4A2160330 for ; Wed, 19 Oct 2022 18:42:17 +0000 (UTC) X-FDA: 80038569114.07.67C1B89 Received: from mail-yw1-f182.google.com (mail-yw1-f182.google.com [209.85.128.182]) by imf06.hostedemail.com (Postfix) with ESMTP id 049B9180035 for ; Wed, 19 Oct 2022 18:42:16 +0000 (UTC) Received: by mail-yw1-f182.google.com with SMTP id 00721157ae682-333a4a5d495so176759257b3.10 for ; Wed, 19 Oct 2022 11:42:16 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20210112; h=cc:to:subject:message-id:date:from:in-reply-to:references :mime-version:from:to:cc:subject:date:message-id:reply-to; bh=pVpbWk4bBR6nw+ZSuDfbXLMU1jc4pYSjC/JFj+X3inQ=; b=YoiHOFl8KBDaxhfE4FWVp0F3P+wbRiWm3ZVBwwYx9MICrivFguDiiv5cZW5NI4kira +VfkooKF5ZN3REa98ypGmgSsKMIkcBMW31cxu7zXMAveGuBwbqq5RcUbOle5R8+pxsha RMKTwKeFt0p/jwjh9csfF6peqGhDf+MJy07S1PV3JrUE3qCuMSw6X/hT3TQBR7lf6mzp xXFEAElFPxGT2wfBBgOJJhK66mxM6WD5zZsb+NV9UZ4scEt2140SRtext481r70394X3 PaZEbrJ1mfBA2++CzUKuaN7Q7nH2eJ93nHAR01qn7pg2+45nZ/C4flq7EKrYrAk2ifN1 epxQ== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=cc:to:subject:message-id:date:from:in-reply-to:references :mime-version:x-gm-message-state:from:to:cc:subject:date:message-id :reply-to; bh=pVpbWk4bBR6nw+ZSuDfbXLMU1jc4pYSjC/JFj+X3inQ=; b=yaQWHqpke9wvAowPLiZxijhcW74h3CmENGBPRWgUn8E5IQclweWvc7zUF8sOOBJy11 5oUZLbbWUiFkWS0/gNjR7145Tv4W8N8vkE7BAgRhxwVqJVD+QM2ukXzCgp0kJFvNG4d4 G6v+TFmeMPR88zY4VAvouQc2f0C885eMrE9SK6yDq/0VOGd+dusOcBsLYMw3j6bxXd3L 0QYMWKYlCqB3oBA4J5p7E78Lvj9UIhWVloe8uv4wbfEh952tATxam6SsfsusJZTIK9e9 EwYQMU6MSh1sG38zJ3BUkHJSxCaLF4/Y+djQ4Sg817Bq1u23/GDBqVDSZQzn/bFFjDkH q1Xg== X-Gm-Message-State: ACrzQf0TAH3adwfXwFEsmx0px7nKextm0NPUPGUgS+uDnAn1WbGaj2Tb IyucoeZqfhWSj9DAjZDNjQqt6npmJVnsBTGkXXgMzA== X-Google-Smtp-Source: AMsMyM6Pe2fz4Ig5qqZ3whp3aVx1Dg3ZQP+klUtMTnCd6iA3J+zPI2VdQMA9MBYc+544+g/g0Iu2ghDNnB4wvR4Khmg= X-Received: by 2002:a81:8283:0:b0:367:a556:e893 with SMTP id s125-20020a818283000000b00367a556e893mr2059965ywf.115.1666204936093; Wed, 19 Oct 2022 11:42:16 -0700 (PDT) MIME-Version: 1.0 References: <20221018200125.848471-1-jthoughton@google.com> In-Reply-To: From: James Houghton Date: Wed, 19 Oct 2022 11:42:04 -0700 Message-ID: Subject: Re: [PATCH] hugetlbfs: don't delete error page from pagecache To: Yang Shi Cc: Mike Kravetz , Muchun Song , Naoya Horiguchi , Miaohe Lin , Andrew Morton , Axel Rasmussen , linux-mm@kvack.org, linux-kernel@vger.kernel.org Content-Type: text/plain; charset="UTF-8" ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1666204937; a=rsa-sha256; cv=none; b=Rza3Q9Swu3GQFnwNLzh8mEVINiBHuqMA9TXIUDmPL4V2UPF3pXXAANzYysETj0d5/JZ2JY izcXtRWxVxltILsXLlT09gcsh6MBD5m2ETeE2veEeM+g1u5/Wv+zM6N6Xz7mRVwP2RDdQb swC/j6SVMMZ3tkgDptFSVmgEtqAgHHU= ARC-Authentication-Results: i=1; imf06.hostedemail.com; dkim=pass header.d=google.com header.s=20210112 header.b=YoiHOFl8; spf=pass (imf06.hostedemail.com: domain of jthoughton@google.com designates 209.85.128.182 as permitted sender) smtp.mailfrom=jthoughton@google.com; dmarc=pass (policy=reject) header.from=google.com ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1666204937; h=from:from:sender:reply-to:subject:subject:date:date: message-id:message-id:to:to:cc:cc:mime-version:mime-version: content-type:content-type:content-transfer-encoding: in-reply-to:in-reply-to:references:references:dkim-signature; bh=pVpbWk4bBR6nw+ZSuDfbXLMU1jc4pYSjC/JFj+X3inQ=; b=Dzbk2kb1W25cYtxhHVrKmlbXJMIY8NY9KTa+04PL83h0897aDh12jiXQa+UhMNByO+Ntvz bnT2Jkc0wlbtBd8qmg4TPATdWduwb8Y8RvdVSX4fhpeIG/gvEDomwJFObg3p+hzjoagXSp HCz6vSP7Kdurw4OOkbyzH+BOkhx98i0= X-Stat-Signature: syefh5f5xgb4caccugc7a6ixqzhrs6xi X-Rspamd-Queue-Id: 049B9180035 Authentication-Results: imf06.hostedemail.com; dkim=pass header.d=google.com header.s=20210112 header.b=YoiHOFl8; spf=pass (imf06.hostedemail.com: domain of jthoughton@google.com designates 209.85.128.182 as permitted sender) smtp.mailfrom=jthoughton@google.com; dmarc=pass (policy=reject) header.from=google.com X-Rspam-User: X-Rspamd-Server: rspam01 X-HE-Tag: 1666204936-954682 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On Wed, Oct 19, 2022 at 11:31 AM Yang Shi wrote: > > On Tue, Oct 18, 2022 at 1:01 PM James Houghton wrote: > > > > This change is very similar to the change that was made for shmem [1], > > and it solves the same problem but for HugeTLBFS instead. > > > > Currently, when poison is found in a HugeTLB page, the page is removed > > from the page cache. That means that attempting to map or read that > > hugepage in the future will result in a new hugepage being allocated > > instead of notifying the user that the page was poisoned. As [1] states, > > this is effectively memory corruption. > > > > The fix is to leave the page in the page cache. If the user attempts to > > use a poisoned HugeTLB page with a syscall, the syscall will fail with > > EIO, the same error code that shmem uses. For attempts to map the page, > > the thread will get a BUS_MCEERR_AR SIGBUS. > > > > [1]: commit a76054266661 ("mm: shmem: don't truncate page if memory failure happens") > > > > Signed-off-by: James Houghton > > Thanks for the patch. Yes, we should do the same thing for hugetlbfs. > When I was working on shmem I did look into hugetlbfs too. But the > problem is we actually make the whole hugetlb page unavailable even > though just one 4K sub page is hwpoisoned. It may be fine to 2M > hugetlb page, but a lot of memory may be a huge waste for 1G hugetlb > page, particular for the page fault path. Right -- it is wasted until a hole is punched or the file is truncated. Although we're wasting the rest of the hugepage for a little longer with this patch, I think it's worth it to have correct behavior. > > So I discussed this with Mike offline last year, and I was told Google > was working on PTE mapped hugetlb page. That should be able to solve > the problem. And we'd like to have the high-granularity hugetlb > mapping support as the predecessor. > > There were some other details, but I can't remember all of them, I > have to refresh my memory by rereading the email discussions... Yes! I am working on this. :) I will send up a series in the coming weeks that implements basic support for high-granularity mapping (HGM). This patch is required for hwpoison semantics to work properly for high-granularity mapping (and, as the patch states, for shared HugeTLB mappings generally). For HGM, if we partially map a hugepage and find poison, faulting on the unmapped bits of it will allocate a new hugepage. By keeping the poisoned page in the pagecache, we correctly give userspace a SIGBUS. I didn't mention this in the commit description because I think this patch is correct on its own. I haven't implemented PAGE_SIZE poisoning of HugeTLB pages yet, but high-granularity mapping unblocks this work. Hopefully that will be ready in the coming months. :) - James Houghton > > > --- > > fs/hugetlbfs/inode.c | 13 ++++++------- > > mm/hugetlb.c | 4 ++++ > > mm/memory-failure.c | 5 ++++- > > 3 files changed, 14 insertions(+), 8 deletions(-) > > > > diff --git a/fs/hugetlbfs/inode.c b/fs/hugetlbfs/inode.c > > index fef5165b73a5..7f836f8f9db1 100644 > > --- a/fs/hugetlbfs/inode.c > > +++ b/fs/hugetlbfs/inode.c > > @@ -328,6 +328,12 @@ static ssize_t hugetlbfs_read_iter(struct kiocb *iocb, struct iov_iter *to) > > } else { > > unlock_page(page); > > > > + if (PageHWPoison(page)) { > > + put_page(page); > > + retval = -EIO; > > + break; > > + } > > + > > /* > > * We have the page, copy it to user space buffer. > > */ > > @@ -1111,13 +1117,6 @@ static int hugetlbfs_migrate_folio(struct address_space *mapping, > > static int hugetlbfs_error_remove_page(struct address_space *mapping, > > struct page *page) > > { > > - struct inode *inode = mapping->host; > > - pgoff_t index = page->index; > > - > > - hugetlb_delete_from_page_cache(page_folio(page)); > > - if (unlikely(hugetlb_unreserve_pages(inode, index, index + 1, 1))) > > - hugetlb_fix_reserve_counts(inode); > > - > > return 0; > > } > > > > diff --git a/mm/hugetlb.c b/mm/hugetlb.c > > index 97896165fd3f..5120a9ccbf5b 100644 > > --- a/mm/hugetlb.c > > +++ b/mm/hugetlb.c > > @@ -6101,6 +6101,10 @@ int hugetlb_mcopy_atomic_pte(struct mm_struct *dst_mm, > > > > ptl = huge_pte_lock(h, dst_mm, dst_pte); > > > > + ret = -EIO; > > + if (PageHWPoison(page)) > > + goto out_release_unlock; > > + > > /* > > * We allow to overwrite a pte marker: consider when both MISSING|WP > > * registered, we firstly wr-protect a none pte which has no page cache > > diff --git a/mm/memory-failure.c b/mm/memory-failure.c > > index 145bb561ddb3..bead6bccc7f2 100644 > > --- a/mm/memory-failure.c > > +++ b/mm/memory-failure.c > > @@ -1080,6 +1080,7 @@ static int me_huge_page(struct page_state *ps, struct page *p) > > int res; > > struct page *hpage = compound_head(p); > > struct address_space *mapping; > > + bool extra_pins = false; > > > > if (!PageHuge(hpage)) > > return MF_DELAYED; > > @@ -1087,6 +1088,8 @@ static int me_huge_page(struct page_state *ps, struct page *p) > > mapping = page_mapping(hpage); > > if (mapping) { > > res = truncate_error_page(hpage, page_to_pfn(p), mapping); > > + /* The page is kept in page cache. */ > > + extra_pins = true; > > unlock_page(hpage); > > } else { > > unlock_page(hpage); > > @@ -1104,7 +1107,7 @@ static int me_huge_page(struct page_state *ps, struct page *p) > > } > > } > > > > - if (has_extra_refcount(ps, p, false)) > > + if (has_extra_refcount(ps, p, extra_pins)) > > res = MF_FAILED; > > > > return res; > > -- > > 2.38.0.413.g74048e4d9e-goog > >