[PATCH] selftest: mm: Test if hugepage does not get leaked during __bio_release_pages()

[PATCH] selftest: mm: Test if hugepage does not get leaked during __bio_release_pages()

[Donet Tom]

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 <donettom@linux.ibm.com>
Signed-off-by: Ritesh Harjani (IBM) <ritesh.list@gmail.com>
---
 tools/testing/selftests/mm/Makefile      |   1 +
 tools/testing/selftests/mm/hugetlb_dio.c | 118 +++++++++++++++++++++++
 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 <stdio.h>
+#include <sys/stat.h>
+#include <stdlib.h>
+#include <fcntl.h>
+#include <stdint.h>
+#include <unistd.h>
+#include <string.h>
+#include <sys/mman.h>
+#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");
+
+	/* 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);
+	if (orig_buffer == MAP_FAILED) {
+		close(fd);
+		ksft_exit_fail_msg("Error mapping memory");
+	}
+	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);
+		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();
+	return 0;
+}
+
-- 
2.39.3

Re: [PATCH] selftest: mm: Test if hugepage does not get leaked during __bio_release_pages()

[kernel test robot]

Hi,

Thanks for your patch.

FYI: kernel test robot notices the stable kernel rule is not satisfied.

The check is based on https://www.kernel.org/doc/html/latest/process/stable-kernel-rules.html#option-1

Rule: add the tag "Cc: stable@vger.kernel.org" in the sign-off area to have the patch automatically included in the stable tree.
Subject: [PATCH] selftest: mm: Test if hugepage does not get leaked during __bio_release_pages()
Link: https://lore.kernel.org/stable/20240523063905.3173-1-donettom%40linux.ibm.com

-- 
0-DAY CI Kernel Test Service
https://github.com/intel/lkp-tests/wiki

Re: [PATCH] selftest: mm: Test if hugepage does not get leaked during __bio_release_pages()

[Andrew Morton]

On Thu, 23 May 2024 01:39:05 -0500 Donet Tom <donettom@linux.ibm.com> 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.
> 

You have stable@vger.kernel.org in the mail headers, so I assume you're
proposing this for backporting.  When doing this, please include 

Cc: <stable@vger.kernel.org>

in the changelog footers and also include a Fixes: target.  I'm
assuming the suitable Fixes: target for this patch is 38b43539d64b?

Re: [PATCH] selftest: mm: Test if hugepage does not get leaked during __bio_release_pages()

[David Hildenbrand]

On 23.05.24 21:13, Andrew Morton wrote:
> On Thu, 23 May 2024 01:39:05 -0500 Donet Tom <donettom@linux.ibm.com> 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.
>>
> 

Two SOF, is there a Co-developed-by: missing?

> You have stable@vger.kernel.org in the mail headers, so I assume you're
> proposing this for backporting.  When doing this, please include
> 
> Cc: <stable@vger.kernel.org>
> 
> in the changelog footers and also include a Fixes: target.  I'm
> assuming the suitable Fixes: target for this patch is 38b43539d64b?

This adds a new selfest to make sure what was fixed (and backported to 
stable) remains fixed.

-- 
Cheers,

David / dhildenb

Re: [PATCH] selftest: mm: Test if hugepage does not get leaked during __bio_release_pages()

[Andrew Morton]

On Thu, 23 May 2024 22:40:25 +0200 David Hildenbrand <david@redhat.com> wrote:

> > You have stable@vger.kernel.org in the mail headers, so I assume you're
> > proposing this for backporting.  When doing this, please include
> > 
> > Cc: <stable@vger.kernel.org>
> > 
> > in the changelog footers and also include a Fixes: target.  I'm
> > assuming the suitable Fixes: target for this patch is 38b43539d64b?
> 
> This adds a new selfest to make sure what was fixed (and backported to 
> stable) remains fixed.

Sure.  But we should provide -stable maintainers guidance for "how far
back to go".  There isn't much point in backporting this into kernels
where it's known to fail!

I'm still thinking that we want this in kernels which have 38b43539d64b?

Re: [PATCH] selftest: mm: Test if hugepage does not get leaked during __bio_release_pages()

[David Hildenbrand]

On 24.05.24 04:57, Andrew Morton wrote:
> On Thu, 23 May 2024 22:40:25 +0200 David Hildenbrand <david@redhat.com> wrote:
> 
>>> You have stable@vger.kernel.org in the mail headers, so I assume you're
>>> proposing this for backporting.  When doing this, please include
>>>
>>> Cc: <stable@vger.kernel.org>
>>>
>>> in the changelog footers and also include a Fixes: target.  I'm
>>> assuming the suitable Fixes: target for this patch is 38b43539d64b?
>>
>> This adds a new selfest to make sure what was fixed (and backported to
>> stable) remains fixed.
> 
> Sure.  But we should provide -stable maintainers guidance for "how far
> back to go".  There isn't much point in backporting this into kernels
> where it's known to fail!

I'm probably missing something important.

1) It's a test that does not fall into the common stable kernels 
categories (see Documentation/process/stable-kernel-rules.rst).

2) If it fails in a kernel *it achieved its goal* of highlighting that 
something serious is broken.

> 
> I'm still thinking that we want this in kernels which have 38b43539d64b?

To hide that the other kernels are seriously broken and miss that fix?

Really (1) this shouldn't be backported. I'm not even sure it should be 
a selftest (sounds more like a reproducer that we usually attach to 
commits, but that's too late). And if people care about backporting it, 
(2) you really want this test to succeed everywhere. Especially also to 
find kernels *without* 38b43539d64b

-- 
Cheers,

David / dhildenb

Re: [PATCH] selftest: mm: Test if hugepage does not get leaked during __bio_release_pages()

[Muhammad Usama Anjum]

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 <donettom@linux.ibm.com>
> Signed-off-by: Ritesh Harjani (IBM) <ritesh.list@gmail.com>
> ---
>  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 <stdio.h>
> +#include <sys/stat.h>
> +#include <stdlib.h>
> +#include <fcntl.h>
> +#include <stdint.h>
> +#include <unistd.h>
> +#include <string.h>
> +#include <sys/mman.h>
> +#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

Re: [PATCH] selftest: mm: Test if hugepage does not get leaked during __bio_release_pages()

[Donet Tom]

On 5/24/24 23:43, Muhammad Usama Anjum wrote:
> 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 <donettom@linux.ibm.com>
>> Signed-off-by: Ritesh Harjani (IBM) <ritesh.list@gmail.com>
>> ---
>>   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 <stdio.h>
>> +#include <sys/stat.h>
>> +#include <stdlib.h>
>> +#include <fcntl.h>
>> +#include <stdint.h>
>> +#include <unistd.h>
>> +#include <string.h>
>> +#include <sys/mman.h>
>> +#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.

Thank you for all your suggestions.  I will make all the changes and send V2.

Thanks
Donet

>> +	return 0;
>> +}
>> +