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Fri, 24 May 2024 18:13:40 +0000 (UTC) Message-ID: Date: Fri, 24 May 2024 11:13:24 -0700 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Cc: Muhammad Usama Anjum , linux-mm@kvack.org, linux-kselftest@vger.kernel.org, linux-kernel@vger.kernel.org, Ritesh Harjani , Mike Rapoport , Muchun Song , David Hildenbrand , stable@vger.kernel.org Subject: Re: [PATCH] selftest: mm: Test if hugepage does not get leaked during __bio_release_pages() To: Donet Tom , Andrew Morton , Shuah Khan , Matthew Wilcox , Tony Battersby References: <20240523063905.3173-1-donettom@linux.ibm.com> Content-Language: en-US From: Muhammad Usama Anjum In-Reply-To: <20240523063905.3173-1-donettom@linux.ibm.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit X-Stat-Signature: 3pibtj3wqqdsfg9w6zanks58zyfp47uw X-Rspamd-Queue-Id: 0D024A0013 X-Rspam-User: X-Rspamd-Server: rspam01 X-HE-Tag: 1716574425-722000 X-HE-Meta: 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 cikvQ3fQ 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 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: Thank you for submitting a patch. On 5/22/24 11:39 PM, Donet Tom wrote: > Commit 1b151e2435fc ("block: Remove special-casing of compound > pages") caused a change in behaviour when releasing the pages > if the buffer does not start at the beginning of the page. This > was because the calculation of the number of pages to release > was incorrect. > This was fixed by commit 38b43539d64b ("block: Fix page refcounts > for unaligned buffers in __bio_release_pages()"). > > We pin the user buffer during direct I/O writes. If this buffer is a > hugepage, bio_release_page() will unpin it and decrement all references > and pin counts at ->bi_end_io. However, if any references to the hugepage > remain post-I/O, the hugepage will not be freed upon unmap, leading > to a memory leak. > > This patch verifies that a hugepage, used as a user buffer for DIO > operations, is correctly freed upon unmapping, regardless of whether > the offsets are aligned or unaligned w.r.t page boundary. > > Test Result Fail Scenario (Without the fix) > -------------------------------------------------------- > []# ./hugetlb_dio > TAP version 13 > 1..4 > No. Free pages before allocation : 7 > No. Free pages after munmap : 7 > ok 1 : Huge pages freed successfully ! > No. Free pages before allocation : 7 > No. Free pages after munmap : 7 > ok 2 : Huge pages freed successfully ! > No. Free pages before allocation : 7 > No. Free pages after munmap : 7 > ok 3 : Huge pages freed successfully ! > No. Free pages before allocation : 7 > No. Free pages after munmap : 6 > not ok 4 : Huge pages not freed! > Totals: pass:3 fail:1 xfail:0 xpass:0 skip:0 error:0 > > Test Result PASS Scenario (With the fix) > --------------------------------------------------------- > []#./hugetlb_dio > TAP version 13 > 1..4 > No. Free pages before allocation : 7 > No. Free pages after munmap : 7 > ok 1 : Huge pages freed successfully ! > No. Free pages before allocation : 7 > No. Free pages after munmap : 7 > ok 2 : Huge pages freed successfully ! > No. Free pages before allocation : 7 > No. Free pages after munmap : 7 > ok 3 : Huge pages freed successfully ! > No. Free pages before allocation : 7 > No. Free pages after munmap : 7 > ok 4 : Huge pages freed successfully ! > Totals: pass:4 fail:0 xfail:0 xpass:0 skip:0 error:0 > > Signed-off-by: Donet Tom > Signed-off-by: Ritesh Harjani (IBM) > --- > tools/testing/selftests/mm/Makefile | 1 + > tools/testing/selftests/mm/hugetlb_dio.c | 118 +++++++++++++++++++++++ Add this test to vm_runtest.sh as all the tests are run from this script in CIs. > 2 files changed, 119 insertions(+) > create mode 100644 tools/testing/selftests/mm/hugetlb_dio.c > > diff --git a/tools/testing/selftests/mm/Makefile b/tools/testing/selftests/mm/Makefile > index eb5f39a2668b..87d8130b3376 100644 > --- a/tools/testing/selftests/mm/Makefile > +++ b/tools/testing/selftests/mm/Makefile > @@ -71,6 +71,7 @@ TEST_GEN_FILES += ksm_functional_tests > TEST_GEN_FILES += mdwe_test > TEST_GEN_FILES += hugetlb_fault_after_madv > TEST_GEN_FILES += hugetlb_madv_vs_map > +TEST_GEN_FILES += hugetlb_dio > > ifneq ($(ARCH),arm64) > TEST_GEN_FILES += soft-dirty > diff --git a/tools/testing/selftests/mm/hugetlb_dio.c b/tools/testing/selftests/mm/hugetlb_dio.c > new file mode 100644 > index 000000000000..6f6587c7913c > --- /dev/null > +++ b/tools/testing/selftests/mm/hugetlb_dio.c > @@ -0,0 +1,118 @@ > +// SPDX-License-Identifier: GPL-2.0 > +/* > + * This program tests for hugepage leaks after DIO writes to a file using a > + * hugepage as the user buffer. During DIO, the user buffer is pinned and > + * should be properly unpinned upon completion. This patch verifies that the > + * kernel correctly unpins the buffer at DIO completion for both aligned and > + * unaligned user buffer offsets (w.r.t page boundary), ensuring the hugepage > + * is freed upon unmapping. > + */ > + > +#define _GNU_SOURCE > +#include > +#include > +#include > +#include > +#include > +#include > +#include > +#include > +#include "vm_util.h" > +#include "../kselftest.h" > + > +void run_dio_using_hugetlb(unsigned int start_off, unsigned int end_off) > +{ > + int fd; > + char *buffer = NULL; > + char *orig_buffer = NULL; > + size_t h_pagesize = 0; > + size_t writesize; > + int free_hpage_b = 0; > + int free_hpage_a = 0; > + > + writesize = end_off - start_off; > + > + /* Get the default huge page size */ > + h_pagesize = default_huge_page_size(); > + if (!h_pagesize) > + ksft_exit_fail_msg("Unable to determine huge page size\n"); > + > + /* Open the file to DIO */ > + fd = open("/tmp", O_TMPFILE | O_RDWR | O_DIRECT); > + if (fd < 0) > + ksft_exit_fail_msg("Error opening file"); Use ksft_exit_fail_perror to print the info about the error > + > + /* Get the free huge pages before allocation */ > + free_hpage_b = get_free_hugepages(); > + if (free_hpage_b == 0) { > + close(fd); > + ksft_exit_skip("No free hugepage, exiting!\n"); > + } > + > + /* Allocate a hugetlb page */ > + orig_buffer = mmap(NULL, h_pagesize, PROT_READ | PROT_WRITE, MAP_PRIVATE > + | MAP_ANONYMOUS | MAP_HUGETLB, -1, 0); Better align the arguments. Put all flags in one line instead of slitting like this > + if (orig_buffer == MAP_FAILED) { > + close(fd); > + ksft_exit_fail_msg("Error mapping memory"); nit: "\n" is missing from here. > + } > + buffer = orig_buffer; > + buffer += start_off; > + > + memset(buffer, 'A', writesize); > + > + /* Write the buffer to the file */ > + if (write(fd, buffer, writesize) != (writesize)) { > + munmap(orig_buffer, h_pagesize); > + close(fd); > + ksft_exit_fail_msg("Error writing to file"); > + } > + > + /* unmap the huge page */ > + munmap(orig_buffer, h_pagesize); > + close(fd); > + > + /* Get the free huge pages after unmap*/ > + free_hpage_a = get_free_hugepages(); > + > + /* > + * If the no. of free hugepages before allocation and after unmap does > + * not match - that means there could still be a page which is pinned. > + */ > + if (free_hpage_a != free_hpage_b) { > + printf("No. Free pages before allocation : %d\n", free_hpage_b); Use ksft_print_msg instead > + printf("No. Free pages after munmap : %d\n", free_hpage_a); > + ksft_test_result_fail(": Huge pages not freed!\n"); > + } else { > + printf("No. Free pages before allocation : %d\n", free_hpage_b); > + printf("No. Free pages after munmap : %d\n", free_hpage_a); > + ksft_test_result_pass(": Huge pages freed successfully !\n"); > + } > +} > + > +int main(void) > +{ > + size_t pagesize = 0; > + > + ksft_print_header(); > + ksft_set_plan(4); > + > + /* Get base page size */ > + pagesize = psize(); > + > + /* start and end is aligned to pagesize */ > + run_dio_using_hugetlb(0, (pagesize * 3)); > + > + /* start is aligned but end is not aligned */ > + run_dio_using_hugetlb(0, (pagesize * 3) - (pagesize / 2)); > + > + /* start is unaligned and end is aligned */ > + run_dio_using_hugetlb(pagesize / 2, (pagesize * 3)); > + > + /* both start and end are unaligned */ > + run_dio_using_hugetlb(pagesize / 2, (pagesize * 3) + (pagesize / 2)); > + > + ksft_finished(); ksft_finished() never returns. Remove the following line. > + return 0; > +} > + -- BR, Muhammad Usama Anjum