Re: [PATCH] selftests/mm: read memory information without popen

["David Hildenbrand (Arm)" <david@kernel.org>]

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.

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