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X-IronPort-AV: E=McAfee;i="6500,9779,10599"; a="309776300" X-IronPort-AV: E=Sophos;i="5.97,240,1669104000"; d="scan'208";a="309776300" Received: from fmsmga001.fm.intel.com ([10.253.24.23]) by orsmga106.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 23 Jan 2023 16:33:55 -0800 X-IronPort-AV: E=McAfee;i="6500,9779,10599"; a="804389693" X-IronPort-AV: E=Sophos;i="5.97,240,1669104000"; d="scan'208";a="804389693" Received: from arechkov-mobl.ger.corp.intel.com (HELO box.shutemov.name) ([10.251.208.243]) by fmsmga001-auth.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 23 Jan 2023 16:33:52 -0800 Received: by box.shutemov.name (Postfix, from userid 1000) id DCBC210942C; Tue, 24 Jan 2023 03:33:49 +0300 (+03) Date: Tue, 24 Jan 2023 03:33:49 +0300 From: kirill.shutemov@linux.intel.com To: Jiaqi Yan Cc: kirill@shutemov.name, shy828301@gmail.com, tongtiangen@huawei.com, tony.luck@intel.com, akpm@linux-foundation.org, wangkefeng.wang@huawei.com, naoya.horiguchi@nec.com, linmiaohe@huawei.com, linux-mm@kvack.org, osalvador@suse.de Subject: Re: [PATCH v9 1/2] mm/khugepaged: recover from poisoned anonymous memory Message-ID: <20230124003349.m64heg7mnqw7snyh@box.shutemov.name> References: <20221205234059.42971-1-jiaqiyan@google.com> <20221205234059.42971-2-jiaqiyan@google.com> <20230119150258.npfadnefkpny5fd3@box.shutemov.name> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: X-Rspam-User: X-Rspamd-Server: rspam04 X-Rspamd-Queue-Id: EE57040014 X-Stat-Signature: 7186indn5gn3ktpypj18e4j85czjgtwu X-HE-Tag: 1674520437-565512 X-HE-Meta: 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 5IyqiUB5 9eMtZQgSLXbfZbBmh4NBKZL74LJLTkDoFiyYX3OZon4GrgeV/wntRJi5+wQUlQRBjMeGfxtBpjDjCkmy4ehF6cOmiCNe5R/0RaqGYvCFgOk6n4apCaUc6fwThCYBq7ovz1c3UnB0WxCtkjmT+kwGsJoTEsvg+yaq6srWS3Hb9GelNkJM= 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 Fri, Jan 20, 2023 at 07:56:15AM -0800, Jiaqi Yan wrote: > On Thu, Jan 19, 2023 at 7:03 AM wrote: > > > > On Mon, Dec 05, 2022 at 03:40:58PM -0800, Jiaqi Yan wrote: > > > Make __collapse_huge_page_copy return whether copying anonymous pages > > > succeeded, and make collapse_huge_page handle the return status. > > > > > > Break existing PTE scan loop into two for-loops. The first loop copies > > > source pages into target huge page, and can fail gracefully when running > > > into memory errors in source pages. If copying all pages succeeds, the > > > second loop releases and clears up these normal pages. Otherwise, the > > > second loop rolls back the page table and page states by: > > > - re-establishing the original PTEs-to-PMD connection. > > > - releasing source pages back to their LRU list. > > > > > > Tested manually: > > > 0. Enable khugepaged on system under test. > > > 1. Start a two-thread application. Each thread allocates a chunk of > > > non-huge anonymous memory buffer. > > > 2. Pick 4 random buffer locations (2 in each thread) and inject > > > uncorrectable memory errors at corresponding physical addresses. > > > 3. Signal both threads to make their memory buffer collapsible, i.e. > > > calling madvise(MADV_HUGEPAGE). > > > 4. Wait and check kernel log: khugepaged is able to recover from poisoned > > > pages and skips collapsing them. > > > 5. Signal both threads to inspect their buffer contents and make sure no > > > data corruption. > > > > > > Signed-off-by: Jiaqi Yan > > > --- > > > include/trace/events/huge_memory.h | 3 +- > > > mm/khugepaged.c | 179 ++++++++++++++++++++++------- > > > 2 files changed, 139 insertions(+), 43 deletions(-) > > > > > > diff --git a/include/trace/events/huge_memory.h b/include/trace/events/huge_memory.h > > > index 35d759d3b0104..5743ae970af31 100644 > > > --- a/include/trace/events/huge_memory.h > > > +++ b/include/trace/events/huge_memory.h > > > @@ -36,7 +36,8 @@ > > > EM( SCAN_ALLOC_HUGE_PAGE_FAIL, "alloc_huge_page_failed") \ > > > EM( SCAN_CGROUP_CHARGE_FAIL, "ccgroup_charge_failed") \ > > > EM( SCAN_TRUNCATED, "truncated") \ > > > - EMe(SCAN_PAGE_HAS_PRIVATE, "page_has_private") \ > > > + EM( SCAN_PAGE_HAS_PRIVATE, "page_has_private") \ > > > + EMe(SCAN_COPY_MC, "copy_poisoned_page") \ > > > > > > #undef EM > > > #undef EMe > > > diff --git a/mm/khugepaged.c b/mm/khugepaged.c > > > index 5a7d2d5093f9c..0f1b9e05e17ec 100644 > > > --- a/mm/khugepaged.c > > > +++ b/mm/khugepaged.c > > > @@ -19,6 +19,7 @@ > > > #include > > > #include > > > #include > > > +#include > > > > > > #include > > > #include > > > @@ -55,6 +56,7 @@ enum scan_result { > > > SCAN_CGROUP_CHARGE_FAIL, > > > SCAN_TRUNCATED, > > > SCAN_PAGE_HAS_PRIVATE, > > > + SCAN_COPY_MC, > > > }; > > > > > > #define CREATE_TRACE_POINTS > > > @@ -530,6 +532,27 @@ static bool is_refcount_suitable(struct page *page) > > > return page_count(page) == expected_refcount; > > > } > > > > > > +/* > > > + * Copies memory with #MC in source page (@from) handled. Returns number > > > + * of bytes not copied if there was an exception; otherwise 0 for success. > > > + * Note handling #MC requires arch opt-in. > > > + */ > > > +static int copy_mc_page(struct page *to, struct page *from) > > > +{ > > > + char *vfrom, *vto; > > > + unsigned long ret; > > > + > > > + vfrom = kmap_local_page(from); > > > + vto = kmap_local_page(to); > > > + ret = copy_mc_to_kernel(vto, vfrom, PAGE_SIZE); > > > + if (ret == 0) > > > + kmsan_copy_page_meta(to, from); > > > + kunmap_local(vto); > > > + kunmap_local(vfrom); > > > + > > > + return ret; > > > +} > > > > > > It is very similar to copy_mc_user_highpage(), but uses > > kmsan_copy_page_meta() instead of kmsan_unpoison_memory(). > > > > Could you explain the difference? I don't quite get it. > > copy_mc_page is actually the MC version of copy_highpage, which uses > kmsan_copy_page_meta instead of kmsan_unpoison_memory. > > My understanding is kmsan_copy_page_meta covers kmsan_unpoison_memory. > When there is no metadata (kmsan_shadow or kmsan_origin), both > kmsan_copy_page_meta and kmsan_unpoison_memory just do > kmsan_internal_unpoison_memory to mark the memory range as > initialized; when there is metadata in src page, kmsan_copy_page_meta > will copy whatever metadata in src to dst. So I think > kmsan_copy_page_meta is the right thing to do. Should we fix copy_mc_user_highpage() then? > > Indentation levels get out of control. Maybe some code restructuring is > > required? > > v10 will change to something like this to reduce 1 level of indentation: > > if (pte_none(pteval) || is_zero_pfn(pte_pfn(pteval))) > continue; > src_page = pte_page(pteval); > if (!PageCompound(src_page)) > release_pte_page(src_page); I hoped for deeper rework. Maybe split the function into several functions and make overall structure more readable? -- Kiryl Shutsemau / Kirill A. Shutemov