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[91.145.109.188]) by smtp.gmail.com with ESMTPSA id q16-20020a2eb4b0000000b0025d75995a07sm268015ljm.24.2022.08.12.00.58.35 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Fri, 12 Aug 2022 00:58:36 -0700 (PDT) Message-ID: <1ec090fa-f93b-c197-e5b3-ff2b0d5862ef@redhat.com> Date: Fri, 12 Aug 2022 10:58:34 +0300 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:91.0) Gecko/20100101 Thunderbird/91.11.0 Subject: Re: [PATCH 2/2] selftests/hmm-tests: Add test for dirty bits To: Alistair Popple , linux-mm@kvack.org, akpm@linux-foundation.org Cc: linux-kernel@vger.kernel.org, "Sierra Guiza, Alejandro (Alex)" , Felix Kuehling , Jason Gunthorpe , John Hubbard , David Hildenbrand , Ralph Campbell , Matthew Wilcox , Karol Herbst , Lyude Paul , Ben Skeggs , Logan Gunthorpe , linuxram@us.ibm.com, paulus@ozlabs.org References: <8f19b172d32be2e889b837f88b1ba070bf2c97ee.1660281458.git-series.apopple@nvidia.com> From: =?UTF-8?Q?Mika_Penttil=c3=a4?= In-Reply-To: <8f19b172d32be2e889b837f88b1ba070bf2c97ee.1660281458.git-series.apopple@nvidia.com> X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Language: en-US Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1660291120; a=rsa-sha256; cv=none; b=HgRWkMr9bhqO2OR5pG9sd67WADIPpkwHvbuAFoDHsogMcX6GDK2fzZQhrPKqv4UHvBFPjW cUNI5VgAjnyALffJto5L6/SfgQ1J3YQBErVwF/ep52BQqurROIV3krlyYWEVwtOhIOCV0t l+ZqSKZjYEkxgcxyDIpk539X0ILYaCw= ARC-Authentication-Results: i=1; imf09.hostedemail.com; dkim=pass header.d=redhat.com header.s=mimecast20190719 header.b=GU5OI1AJ; dmarc=pass (policy=none) header.from=redhat.com; spf=pass (imf09.hostedemail.com: domain of mpenttil@redhat.com designates 170.10.129.124 as permitted sender) smtp.mailfrom=mpenttil@redhat.com ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1660291120; 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:content-transfer-encoding: in-reply-to:in-reply-to:references:references:dkim-signature; bh=gB9VejbuR5ze7FfPP0W1PFrmHALsvu1Qjkp8cIXk/lY=; b=m/OP7uCO3/wbaebk5AbnM+lBpetntZTNiEu0LqC4HHyRbEPdSzi1i/s2ydbDXmi/DL9yw2 Y+csPy/TLBO3KAKp7CdWpYSjnivb/Qkm4z88R7/DFZoo0ruZh3bp/RHGWlm4+iiIx67ldF P4QG47gd4iyirfPOmbm2JnB3Expq4cg= X-Rspamd-Server: rspam05 X-Rspamd-Queue-Id: F2887140197 Authentication-Results: imf09.hostedemail.com; dkim=pass header.d=redhat.com header.s=mimecast20190719 header.b=GU5OI1AJ; dmarc=pass (policy=none) header.from=redhat.com; spf=pass (imf09.hostedemail.com: domain of mpenttil@redhat.com designates 170.10.129.124 as permitted sender) smtp.mailfrom=mpenttil@redhat.com X-Rspam-User: X-Stat-Signature: op86ezy58jo7fdemos7af9z9dq6cay53 X-HE-Tag: 1660291119-359589 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: Hi Alistair! On 12.8.2022 8.22, Alistair Popple wrote: > We were not correctly copying PTE dirty bits to pages during > migrate_vma_setup() calls. This could potentially lead to data loss, so > add a test for this. > > Signed-off-by: Alistair Popple > --- > tools/testing/selftests/vm/hmm-tests.c | 124 ++++++++++++++++++++++++++- > 1 file changed, 124 insertions(+) > > diff --git a/tools/testing/selftests/vm/hmm-tests.c b/tools/testing/selftests/vm/hmm-tests.c > index 529f53b..70fdb49 100644 > --- a/tools/testing/selftests/vm/hmm-tests.c > +++ b/tools/testing/selftests/vm/hmm-tests.c > @@ -1200,6 +1200,130 @@ TEST_F(hmm, migrate_multiple) > } > } > > +static char cgroup[] = "/sys/fs/cgroup/hmm-test-XXXXXX"; > +static int write_cgroup_param(char *cgroup_path, char *param, long value) > +{ > + int ret; > + FILE *f; > + char *filename; > + > + if (asprintf(&filename, "%s/%s", cgroup_path, param) < 0) > + return -1; > + > + f = fopen(filename, "w"); > + if (!f) { > + ret = -1; > + goto out; > + } > + > + ret = fprintf(f, "%ld\n", value); > + if (ret < 0) > + goto out1; > + > + ret = 0; > + > +out1: > + fclose(f); > +out: > + free(filename); > + > + return ret; > +} > + > +static int setup_cgroup(void) > +{ > + pid_t pid = getpid(); > + int ret; > + > + if (!mkdtemp(cgroup)) > + return -1; > + > + ret = write_cgroup_param(cgroup, "cgroup.procs", pid); > + if (ret) > + return ret; > + > + return 0; > +} > + > +static int destroy_cgroup(void) > +{ > + pid_t pid = getpid(); > + int ret; > + > + ret = write_cgroup_param("/sys/fs/cgroup/cgroup.procs", > + "cgroup.proc", pid); > + if (ret) > + return ret; > + > + if (rmdir(cgroup)) > + return -1; > + > + return 0; > +} > + > +/* > + * Try and migrate a dirty page that has previously been swapped to disk. This > + * checks that we don't loose dirty bits. > + */ > +TEST_F(hmm, migrate_dirty_page) > +{ > + struct hmm_buffer *buffer; > + unsigned long npages; > + unsigned long size; > + unsigned long i; > + int *ptr; > + int tmp = 0; > + > + npages = ALIGN(HMM_BUFFER_SIZE, self->page_size) >> self->page_shift; > + ASSERT_NE(npages, 0); > + size = npages << self->page_shift; > + > + buffer = malloc(sizeof(*buffer)); > + ASSERT_NE(buffer, NULL); > + > + buffer->fd = -1; > + buffer->size = size; > + buffer->mirror = malloc(size); > + ASSERT_NE(buffer->mirror, NULL); > + > + ASSERT_EQ(setup_cgroup(), 0); > + > + buffer->ptr = mmap(NULL, size, > + PROT_READ | PROT_WRITE, > + MAP_PRIVATE | MAP_ANONYMOUS, > + buffer->fd, 0); > + ASSERT_NE(buffer->ptr, MAP_FAILED); > + > + /* Initialize buffer in system memory. */ > + for (i = 0, ptr = buffer->ptr; i < size / sizeof(*ptr); ++i) > + ptr[i] = 0; > + > + ASSERT_FALSE(write_cgroup_param(cgroup, "memory.reclaim", 1UL<<30)); > + > + /* Fault pages back in from swap as clean pages */ > + for (i = 0, ptr = buffer->ptr; i < size / sizeof(*ptr); ++i) > + tmp += ptr[i]; > + > + /* Dirty the pte */ > + for (i = 0, ptr = buffer->ptr; i < size / sizeof(*ptr); ++i) > + ptr[i] = i; > + The anon pages are quite likely in memory at this point, and dirty in pte. > + /* > + * Attempt to migrate memory to device, which should fail because > + * hopefully some pages are backed by swap storage. > + */ > + ASSERT_TRUE(hmm_migrate_sys_to_dev(self->fd, buffer, npages)); And pages marked dirty also now. But could you elaborate how and where the above fails in more detail, couldn't immediately see it... > + > + ASSERT_FALSE(write_cgroup_param(cgroup, "memory.reclaim", 1UL<<30)); > + > + /* Check we still see the updated data after restoring from swap. */ > + for (i = 0, ptr = buffer->ptr; i < size / sizeof(*ptr); ++i) > + ASSERT_EQ(ptr[i], i); > + > + hmm_buffer_free(buffer); > + destroy_cgroup(); > +} > + > /* > * Read anonymous memory multiple times. > */ --Mika