From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 96F7013C9C9 for ; Thu, 13 Jun 2024 07:57:05 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1718265425; cv=none; b=G97yXgw1Q12kyYE5ybf8sm0nHvzBcfHmerXSXbmpIu4qubGAsBb90Ipl1f3k0pnmDbgcB8kWNfnBfB+KqdbOqK0waADwxV7YOezzmID7KBBwrVqPrYxHFUSvj24XB7rPwiYhqCHDdzBsucY8m2mVgzXFvQp8BSAlznDUmgtovZI= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1718265425; c=relaxed/simple; bh=O+OLNe4V6CSNz50eNyaDVPLFOAOegb6tNKP3yL3vbEc=; h=Subject:To:Cc:From:Date:Message-ID:MIME-Version:Content-Type; b=ffD+J10i7HcnI6u5RPdMGsiur26O87OkCCdLkfH/wOtKLWt3hzX1ZIYDECvrM/kMUNrRqIw52eBculCDL48QfD6R2gN3SqqjPvBwI/KEp0UIKmzMr9ZJkA6S1XBRPBWwaM/8PWKZ58zZQg/13Z2fpvGOS8BJFqvjgG1nMwbdvDI= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=E7bvOSn3; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b="E7bvOSn3" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 1BDE1C2BBFC; Thu, 13 Jun 2024 07:57:04 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1718265425; bh=O+OLNe4V6CSNz50eNyaDVPLFOAOegb6tNKP3yL3vbEc=; h=Subject:To:Cc:From:Date:From; b=E7bvOSn39xZN3lUJLXLcic04vk6gqklqD6MP1LCr468rzjpKMLJbdiV5OR/1eHC8R Rqx/xE7LjiB/A05j4lN4NhJqWPEao6s98RtKA4yGyv8e4cBy/qYnl7d4nLfIZzMmYg fxvflxusAzVYBLyMD3ZduQmka3FLKfej+lvKI/PI= Subject: FAILED: patch "[PATCH] selftests/mm: compaction_test: fix bogus test success and" failed to apply to 5.4-stable tree To: dev.jain@arm.com,akpm@linux-foundation.org,anshuman.khandual@arm.com,shuah@kernel.org,sjayaram@akamai.com,stable@vger.kernel.org Cc: From: Date: Thu, 13 Jun 2024 09:56:53 +0200 Message-ID: <2024061353-scanner-unusable-1d09@gregkh> Precedence: bulk X-Mailing-List: stable@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=ANSI_X3.4-1968 Content-Transfer-Encoding: 8bit The patch below does not apply to the 5.4-stable tree. If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to . To reproduce the conflict and resubmit, you may use the following commands: git fetch https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/ linux-5.4.y git checkout FETCH_HEAD git cherry-pick -x fb9293b6b0156fbf6ab97a1625d99a29c36d9f0c # git commit -s git send-email --to '' --in-reply-to '2024061353-scanner-unusable-1d09@gregkh' --subject-prefix 'PATCH 5.4.y' HEAD^.. Possible dependencies: fb9293b6b015 ("selftests/mm: compaction_test: fix bogus test success and reduce probability of OOM-killer invocation") 9ad665ef55ea ("selftests/mm: compaction_test: fix incorrect write of zero to nr_hugepages") d4202e66a4b1 ("selftests/mm: compaction_test: fix bogus test success on Aarch64") 69e545edbe8b ("selftests/mm: ksft_exit functions do not return") f3b7568c4942 ("selftests/mm: log a consistent test name for check_compaction") 9c1490d911f8 ("selftests/mm: log skipped compaction test as a skip") 8c9eea721a98 ("selftests/mm: skip test if application doesn't has root privileges") 9a21701edc41 ("selftests/mm: conform test to TAP format output") cb6e7cae1886 ("selftests/mm: gup_test: conform test to TAP format output") 019b277b680f ("selftests: mm: skip whole test instead of failure") 46fd75d4a3c9 ("selftests: mm: add pagemap ioctl tests") 05f1edac8009 ("selftests/mm: run all tests from run_vmtests.sh") 000303329752 ("selftests/mm: make migration test robust to failure") f6dd4e223d87 ("selftests/mm: skip soft-dirty tests on arm64") ba91e7e5d15a ("selftests/mm: add tests for HWPOISON hugetlbfs read") 63773d2b593d ("Merge mm-hotfixes-stable into mm-stable to pick up depended-upon changes.") thanks, greg k-h ------------------ original commit in Linus's tree ------------------ >From fb9293b6b0156fbf6ab97a1625d99a29c36d9f0c Mon Sep 17 00:00:00 2001 From: Dev Jain Date: Tue, 21 May 2024 13:13:58 +0530 Subject: [PATCH] selftests/mm: compaction_test: fix bogus test success and reduce probability of OOM-killer invocation Reset nr_hugepages to zero before the start of the test. If a non-zero number of hugepages is already set before the start of the test, the following problems arise: - The probability of the test getting OOM-killed increases. Proof: The test wants to run on 80% of available memory to prevent OOM-killing (see original code comments). Let the value of mem_free at the start of the test, when nr_hugepages = 0, be x. In the other case, when nr_hugepages > 0, let the memory consumed by hugepages be y. In the former case, the test operates on 0.8 * x of memory. In the latter, the test operates on 0.8 * (x - y) of memory, with y already filled, hence, memory consumed is y + 0.8 * (x - y) = 0.8 * x + 0.2 * y > 0.8 * x. Q.E.D - The probability of a bogus test success increases. Proof: Let the memory consumed by hugepages be greater than 25% of x, with x and y defined as above. The definition of compaction_index is c_index = (x - y)/z where z is the memory consumed by hugepages after trying to increase them again. In check_compaction(), we set the number of hugepages to zero, and then increase them back; the probability that they will be set back to consume at least y amount of memory again is very high (since there is not much delay between the two attempts of changing nr_hugepages). Hence, z >= y > (x/4) (by the 25% assumption). Therefore, c_index = (x - y)/z <= (x - y)/y = x/y - 1 < 4 - 1 = 3 hence, c_index can always be forced to be less than 3, thereby the test succeeding always. Q.E.D Link: https://lkml.kernel.org/r/20240521074358.675031-4-dev.jain@arm.com Fixes: bd67d5c15cc1 ("Test compaction of mlocked memory") Signed-off-by: Dev Jain Cc: Cc: Anshuman Khandual Cc: Shuah Khan Cc: Sri Jayaramappa Signed-off-by: Andrew Morton diff --git a/tools/testing/selftests/mm/compaction_test.c b/tools/testing/selftests/mm/compaction_test.c index 5e9bd1da9370..e140558e6f53 100644 --- a/tools/testing/selftests/mm/compaction_test.c +++ b/tools/testing/selftests/mm/compaction_test.c @@ -82,13 +82,16 @@ int prereq(void) return -1; } -int check_compaction(unsigned long mem_free, unsigned long hugepage_size) +int check_compaction(unsigned long mem_free, unsigned long hugepage_size, + unsigned long initial_nr_hugepages) { unsigned long nr_hugepages_ul; int fd, ret = -1; int compaction_index = 0; - char initial_nr_hugepages[20] = {0}; char nr_hugepages[20] = {0}; + char init_nr_hugepages[20] = {0}; + + sprintf(init_nr_hugepages, "%lu", initial_nr_hugepages); /* We want to test with 80% of available memory. Else, OOM killer comes in to play */ @@ -102,23 +105,6 @@ int check_compaction(unsigned long mem_free, unsigned long hugepage_size) goto out; } - if (read(fd, initial_nr_hugepages, sizeof(initial_nr_hugepages)) <= 0) { - ksft_print_msg("Failed to read from /proc/sys/vm/nr_hugepages: %s\n", - strerror(errno)); - goto close_fd; - } - - lseek(fd, 0, SEEK_SET); - - /* Start with the initial condition of 0 huge pages*/ - if (write(fd, "0", sizeof(char)) != sizeof(char)) { - ksft_print_msg("Failed to write 0 to /proc/sys/vm/nr_hugepages: %s\n", - strerror(errno)); - goto close_fd; - } - - lseek(fd, 0, SEEK_SET); - /* Request a large number of huge pages. The Kernel will allocate as much as it can */ if (write(fd, "100000", (6*sizeof(char))) != (6*sizeof(char))) { @@ -146,8 +132,8 @@ int check_compaction(unsigned long mem_free, unsigned long hugepage_size) lseek(fd, 0, SEEK_SET); - if (write(fd, initial_nr_hugepages, strlen(initial_nr_hugepages)) - != strlen(initial_nr_hugepages)) { + if (write(fd, init_nr_hugepages, strlen(init_nr_hugepages)) + != strlen(init_nr_hugepages)) { ksft_print_msg("Failed to write value to /proc/sys/vm/nr_hugepages: %s\n", strerror(errno)); goto close_fd; @@ -171,6 +157,41 @@ int check_compaction(unsigned long mem_free, unsigned long hugepage_size) return ret; } +int set_zero_hugepages(unsigned long *initial_nr_hugepages) +{ + int fd, ret = -1; + char nr_hugepages[20] = {0}; + + fd = open("/proc/sys/vm/nr_hugepages", O_RDWR | O_NONBLOCK); + if (fd < 0) { + ksft_print_msg("Failed to open /proc/sys/vm/nr_hugepages: %s\n", + strerror(errno)); + goto out; + } + if (read(fd, nr_hugepages, sizeof(nr_hugepages)) <= 0) { + ksft_print_msg("Failed to read from /proc/sys/vm/nr_hugepages: %s\n", + strerror(errno)); + goto close_fd; + } + + lseek(fd, 0, SEEK_SET); + + /* Start with the initial condition of 0 huge pages */ + if (write(fd, "0", sizeof(char)) != sizeof(char)) { + ksft_print_msg("Failed to write 0 to /proc/sys/vm/nr_hugepages: %s\n", + strerror(errno)); + goto close_fd; + } + + *initial_nr_hugepages = strtoul(nr_hugepages, NULL, 10); + ret = 0; + + close_fd: + close(fd); + + out: + return ret; +} int main(int argc, char **argv) { @@ -181,6 +202,7 @@ int main(int argc, char **argv) unsigned long mem_free = 0; unsigned long hugepage_size = 0; long mem_fragmentable_MB = 0; + unsigned long initial_nr_hugepages; ksft_print_header(); @@ -189,6 +211,10 @@ int main(int argc, char **argv) ksft_set_plan(1); + /* Start the test without hugepages reducing mem_free */ + if (set_zero_hugepages(&initial_nr_hugepages)) + ksft_exit_fail(); + lim.rlim_cur = RLIM_INFINITY; lim.rlim_max = RLIM_INFINITY; if (setrlimit(RLIMIT_MEMLOCK, &lim)) @@ -232,7 +258,8 @@ int main(int argc, char **argv) entry = entry->next; } - if (check_compaction(mem_free, hugepage_size) == 0) + if (check_compaction(mem_free, hugepage_size, + initial_nr_hugepages) == 0) ksft_exit_pass(); ksft_exit_fail();