From: warren.xiong <warren.xiong@ugreen.com>
To: david <david@kernel.org>, akpm <akpm@linux-foundation.org>,
shuah <shuah@kernel.org>
Cc: ljs <ljs@kernel.org>, liam <liam@infradead.org>,
vbabka <vbabka@kernel.org>, rppt <rppt@kernel.org>,
surenb <surenb@google.com>, mhocko <mhocko@suse.com>,
linux-mm <linux-mm@kvack.org>,
linux-kselftest <linux-kselftest@vger.kernel.org>,
linux-kernel <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH] selftests/mm: read memory information without popen
Date: Tue, 4 Aug 2026 20:07:47 +0800 [thread overview]
Message-ID: <F297CB3DADE37E96+202608042007461850804@ugreen.com> (raw)
In-Reply-To: 9dc3b457-65aa-40ba-99a1-7c703facbd32@kernel.org
--------------
warren.xiong
>On 8/3/26 03:30, Warren Xiong wrote:
>> read_memory_info() invokes two shell pipelines to obtain MemFree and
>> Hugepagesize from /proc/meminfo. It does not check whether popen()
>> returns NULL before passing the result to fgets(), and it does not call
>> pclose() when fgets() fails.
>>
>> Open /proc/meminfo directly and obtain both values in a single pass.
>> This removes the unchecked NULL path, closes the file on all paths, and
>> avoids dependencies on external commands.
>>
>> The compaction test continues to pass after this change.
>>
>> Signed-off-by: Warren Xiong <warren.xiong@ugreen.com>
>> ---
>> tools/testing/selftests/mm/compaction_test.c | 43 +++++++++++++++++-----------
>> 1 file changed, 27 insertions(+), 16 deletions(-)
>>
>> diff --git a/tools/testing/selftests/mm/compaction_test.c b/tools/testing/selftests/mm/compaction_test.c
>> index 5b58258..0df2000 100644
>> --- a/tools/testing/selftests/mm/compaction_test.c
>> +++ b/tools/testing/selftests/mm/compaction_test.c
>> @@ -7,6 +7,7 @@
>> * allocated.
>> */
>>
>> +#include <stdbool.h>
>> #include <stdio.h>
>> #include <stdlib.h>
>> #include <sys/mman.h>
>> @@ -29,30 +30,40 @@ struct map_list {
>>
>> int read_memory_info(unsigned long *memfree, unsigned long *hugepagesize)
>> {
>
>Looks much better indeed.
>
>> - char buffer[256] = {0};
>> - char *cmd = "cat /proc/meminfo | grep -i memfree | grep -o '[0-9]*'";
>> - FILE *cmdfile = popen(cmd, "r");
>> + char buffer[256];
>> + bool memfree_found = false;
>> + bool hugepagesize_found = false;
>> + FILE *file;
>> + int ret = -1;
>>
>> - if (!(fgets(buffer, sizeof(buffer), cmdfile))) {
>> - ksft_print_msg("Failed to read meminfo: %s\n", strerror(errno));
>> + file = fopen("/proc/meminfo", "r");
>> + if (!file) {
>> + ksft_print_msg("Failed to open /proc/meminfo: %s\n",
>> + strerror(errno));
>> return -1;
>> }
>>
>> - pclose(cmdfile);
>> + while (fgets(buffer, sizeof(buffer), file)) {
>> + if (sscanf(buffer, "MemFree: %lu kB", memfree) == 1)
>> + memfree_found = true;
>> + else if (sscanf(buffer, "Hugepagesize: %lu kB",
>> + hugepagesize) == 1)
>> + hugepagesize_found = true;
>Instead of these bools you could just have a hit-count.
Thanks for the review.
Agreed, a hit count is sufficient here and makes the code simpler. I
have incorporated this change and will send v2 shortly.
Thanks,
Warren
>
>Like the following on top:
>
>diff --git a/tools/testing/selftests/mm/compaction_test.c b/tools/testing/selftests/mm/compaction_test.c
>index 0df2000f4a2b1..30d4ace7155ae 100644
>--- a/tools/testing/selftests/mm/compaction_test.c
>+++ b/tools/testing/selftests/mm/compaction_test.c
>@@ -7,7 +7,6 @@
> * allocated.
> */
>
>-#include <stdbool.h>
> #include <stdio.h>
> #include <stdlib.h>
> #include <sys/mman.h>
>@@ -31,8 +30,7 @@ struct map_list {
> int read_memory_info(unsigned long *memfree, unsigned long *hugepagesize)
> {
> char buffer[256];
>- bool memfree_found = false;
>- bool hugepagesize_found = false;
>+ int found = 0;
> FILE *file;
> int ret = -1;
>
>@@ -43,24 +41,19 @@ int read_memory_info(unsigned long *memfree, unsigned long *hugepagesize)
> return -1;
> }
>
>- while (fgets(buffer, sizeof(buffer), file)) {
>- if (sscanf(buffer, "MemFree: %lu kB", memfree) == 1)
>- memfree_found = true;
>- else if (sscanf(buffer, "Hugepagesize: %lu kB",
>- hugepagesize) == 1)
>- hugepagesize_found = true;
>-
>- if (memfree_found && hugepagesize_found) {
>- ret = 0;
>- break;
>- }
>+ while (fgets(buffer, sizeof(buffer), file) && found != 2) {
>+ if (sscanf(buffer, "MemFree: %lu kB", memfree) == 1 ||
>+ sscanf(buffer, "Hugepagesize: %lu kB", hugepagesize) == 1)
>+ found++;
> }
>
> if (ferror(file))
> ksft_print_msg("Failed to read /proc/meminfo: %s\n",
> strerror(errno));
>- else if (ret)
>+ else if (found != 2)
> ksft_print_msg("Failed to parse /proc/meminfo\n");
>+ else
>+ ret = 0;
>
> fclose(file);
> return ret;
>
>
>--
>Cheers,
>
>David
>
next prev parent reply other threads:[~2026-08-04 12:08 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-08-03 1:30 [PATCH] selftests/mm: read memory information without popen Warren Xiong
2026-08-04 9:48 ` Mike Rapoport
2026-08-04 11:15 ` David Hildenbrand (Arm)
2026-08-04 12:07 ` warren.xiong [this message]
2026-08-04 12:16 ` [PATCH v2] " Warren Xiong
2026-08-04 12:21 ` David Hildenbrand (Arm)
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