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Thu, 23 May 2024 11:02:39 +0800 Subject: Re: [PATCH v3 5/5] mm/memory-failure: send SIGBUS in the event of thp split fail To: Jane Chu , , , , , References: <20240521235429.2368017-1-jane.chu@oracle.com> <20240521235429.2368017-6-jane.chu@oracle.com> From: Miaohe Lin Message-ID: Date: Thu, 23 May 2024 11:02:38 +0800 User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:78.0) Gecko/20100101 Thunderbird/78.6.0 MIME-Version: 1.0 In-Reply-To: <20240521235429.2368017-6-jane.chu@oracle.com> Content-Type: text/plain; charset="utf-8" Content-Language: en-US Content-Transfer-Encoding: 7bit X-Originating-IP: [10.173.135.154] X-ClientProxiedBy: dggems703-chm.china.huawei.com (10.3.19.180) To canpemm500002.china.huawei.com (7.192.104.244) X-Rspamd-Server: rspam03 X-Rspamd-Queue-Id: D7EB4180013 X-Rspam-User: X-Stat-Signature: j64umrd6qpw48pr9hpu3of7imcfee45i X-HE-Tag: 1716433365-56066 X-HE-Meta: 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 u2yxdjwj TzI/TbuBNSNEcwFxZfPnVSW3NEVt1ghUsi/TcSQisKGThhZbF1LGSIWz8golhKZBjdoTgPvXSuX3jVkJSMqg3mMaflIYvEFe6OymNXCda3KOOXlWqaqZ4ybB6uYIbtD6CXgkH0DwvVqAY8KcjvXRclsGuRYfFnDtDggYYYYF1l40P/Itoo6KMKBXZaWrEw9mCwl6mphHHslVAv9rRiPSUv+KUUFV2hvhLkKW34DtYasomtDWYyvTqhneW2A== 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: List-Subscribe: List-Unsubscribe: On 2024/5/22 7:54, Jane Chu wrote: > While handling hwpoison in a THP page, it is possible that > try_to_split_thp_page() fails. For example, when the THP page has > been RDMA pinned. At this point, the kernel cannot isolate the > poisoned THP page, all it could do is to send a SIGBUS to the user > process with meaningful payload to give user-level recovery a chance. > Thanks for your patch. > Signed-off-by: Jane Chu > --- > mm/memory-failure.c | 35 ++++++++++++++++++++++++++++++----- > 1 file changed, 30 insertions(+), 5 deletions(-) > > diff --git a/mm/memory-failure.c b/mm/memory-failure.c > index 794196951a04..a14d56e66902 100644 > --- a/mm/memory-failure.c > +++ b/mm/memory-failure.c > @@ -1706,7 +1706,12 @@ static int identify_page_state(unsigned long pfn, struct page *p, > return page_action(ps, p, pfn); > } > > -static int try_to_split_thp_page(struct page *page) > +/* > + * When 'release' is 'false', it means that if thp split has failed, > + * there is still more to do, hence the page refcount we took earlier > + * is still needed. > + */ > +static int try_to_split_thp_page(struct page *page, bool release) > { > int ret; > > @@ -1714,7 +1719,7 @@ static int try_to_split_thp_page(struct page *page) > ret = split_huge_page(page); > unlock_page(page); > > - if (unlikely(ret)) > + if (ret && release) > put_page(page); Is "unlikely" still needed? > > return ret; > @@ -2187,6 +2192,24 @@ static int memory_failure_dev_pagemap(unsigned long pfn, int flags, > return rc; > } > > +/* > + * The calling condition is as such: thp split failed, page might have > + * been RDMA pinned, not much can be done for recovery. > + * But a SIGBUS should be delivered with vaddr provided so that the user > + * application has a chance to recover. Also, application processes' > + * election for MCE early killed will be honored. > + */ > +static int kill_procs_now(struct page *p, unsigned long pfn, int flags, > + struct folio *folio) > +{ > + LIST_HEAD(tokill); > + > + collect_procs(folio, p, &tokill, flags & MF_ACTION_REQUIRED); > + kill_procs(&tokill, true, pfn, flags); > + > + return -EHWPOISON; > +} > + > /** > * memory_failure - Handle memory failure of a page. > * @pfn: Page Number of the corrupted page > @@ -2328,8 +2351,10 @@ int memory_failure(unsigned long pfn, int flags) > * page is a valid handlable page. > */ > folio_set_has_hwpoisoned(folio); > - if (try_to_split_thp_page(p) < 0) { > - res = action_result(pfn, MF_MSG_UNSPLIT_THP, MF_IGNORED); > + if (try_to_split_thp_page(p, false) < 0) { > + res = kill_procs_now(p, pfn, flags, folio); No strong opinion but we might remove the return value of kill_procs_now as it always return -EHWPOISON? We could simply set res to -EHWPOISON here. Besides from above possible nits, this patch looks good to me. Acked-by: Miaohe Lin Thanks. .