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Sun, 5 May 2024 15:00:20 +0800 Subject: Re: [PATCH 3/3] mm/memory-failure: send SIGBUS in the event of thp split fail To: Jane Chu , , , , References: <20240501232458.3919593-1-jane.chu@oracle.com> <20240501232458.3919593-4-jane.chu@oracle.com> From: Miaohe Lin Message-ID: <038cffc0-e027-b518-460f-40099819c588@huawei.com> Date: Sun, 5 May 2024 15:00:20 +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: <20240501232458.3919593-4-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: dggems705-chm.china.huawei.com (10.3.19.182) To canpemm500002.china.huawei.com (7.192.104.244) X-Stat-Signature: 1drii61bj1eidko83e3kddsmbxyjcbeq X-Rspamd-Queue-Id: D8CBF180002 X-Rspamd-Server: rspam10 X-Rspam-User: X-HE-Tag: 1714892425-81927 X-HE-Meta: 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 2ei7t+g5 UuK+CjMO2POJI+8q1X3EC9wgq9FFAy6yWzERKsf92Z99QCaayBgrH6bO/xy2AlPM0Hk6euPmtAzmYR5LFauvgJT3N2LFJw32Fr98qou1bNj/unv27kDkaFb3JC79D7ck7EeA72ef+u6zwoBbaetTLft0NHXuMdhKSpravCBWuEyfwK+/9QURd2vAlMbAveLu6mPJyuidjGUAnfSDth7qDAe3QpqXODYWySKrA 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 2024/5/2 7:24, Jane Chu wrote: > When handle hwpoison in a GUP longterm pin'ed thp page, > try_to_split_thp_page() will fail. And at this point, there is little else > the kernel could do except sending a SIGBUS to the user process, thus > give it a chance to recover. > > Signed-off-by: Jane Chu Thanks for your patch. Some comments below. > --- > mm/memory-failure.c | 36 ++++++++++++++++++++++++++++++++++++ > 1 file changed, 36 insertions(+) > > diff --git a/mm/memory-failure.c b/mm/memory-failure.c > index 7fcf182abb96..67f4d24a98e7 100644 > --- a/mm/memory-failure.c > +++ b/mm/memory-failure.c > @@ -2168,6 +2168,37 @@ 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 GUP longterm 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 page *hpage) > +{ > + struct folio *folio = page_folio(hpage); > + LIST_HEAD(tokill); > + int res = -EHWPOISON; > + > + /* deal with user pages only */ > + if (PageReserved(p) || PageSlab(p) || PageTable(p) || PageOffline(p)) > + res = -EBUSY; > + if (!(PageLRU(hpage) || PageHuge(p))) > + res = -EBUSY; Above checks seems unneeded. We already know it's thp? > + > + if (res == -EHWPOISON) { > + collect_procs(folio, p, &tokill, flags & MF_ACTION_REQUIRED); > + kill_procs(&tokill, true, pfn, flags); > + } > + > + if (flags & MF_COUNT_INCREASED) > + put_page(p); This if block is broken. put_page() has been done when try_to_split_thp_page() fails? > + action_result is missing? > + return res; > +} > + > /** > * memory_failure - Handle memory failure of a page. > * @pfn: Page Number of the corrupted page > @@ -2297,6 +2328,11 @@ int memory_failure(unsigned long pfn, int flags) > */ > SetPageHasHWPoisoned(hpage); > if (try_to_split_thp_page(p) < 0) { Should hwpoison_filter() be called in this case? > + if (flags & MF_ACTION_REQUIRED) { > + pr_err("%#lx: thp split failed\n", pfn); > + res = kill_procs_now(p, pfn, flags, hpage); Can we use hwpoison_user_mappings() directly here? Thanks. . > + goto unlock_mutex; > + } > res = action_result(pfn, MF_MSG_UNSPLIT_THP, MF_IGNORED); > goto unlock_mutex; > } >