selftests: cachestat: add tests for mmap, refactor and enhance mmap test for cachesta...

Add a cohesive test case that verifies cachestat behavior with
memory-mapped files using mmap().  Also refactor the test logic to reduce
redundancy, improve error reporting, and clarify failure messages for both
shmem and mmap file types.

[akpm@linux-foundation.org: coding-style cleanups]
Link: https://lkml.kernel.org/r/20250709174657.6916-1-suresh.k.chandrappa@gmail.com
Signed-off-by: Suresh K C <suresh.k.chandrappa@gmail.com>
Reviewed-by: Joshua Hahn <joshua.hahnjy@gmail.com>
Tested-by: Nhat Pham <nphamcs@gmail.com>
Acked-by: Nhat Pham <nphamcs@gmail.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Shuah Khan <shuah@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

diff --git a/tools/testing/selftests/cachestat/test_cachestat.c b/tools/testing/selftests/cachestat/test_cachestat.c
index 632ab44737ec3afca5412172e6df67cff87b1e28..c952640f163b5a2c6a7b03d36db5f2eb84061fd7 100644 (file)
--- a/tools/testing/selftests/cachestat/test_cachestat.c
+++ b/tools/testing/selftests/cachestat/test_cachestat.c
@@ -33,6 +33,11 @@ void print_cachestat(struct cachestat *cs)
        cs->nr_evicted, cs->nr_recently_evicted);
 }
 
+enum file_type {
+       FILE_MMAP,
+       FILE_SHMEM
+};
+
 bool write_exactly(int fd, size_t filesize)
 {
        int random_fd = open("/dev/urandom", O_RDONLY);
@@ -201,8 +206,20 @@ out1:
 out:
        return ret;
 }
+const char *file_type_str(enum file_type type)
+{
+       switch (type) {
+       case FILE_SHMEM:
+               return "shmem";
+       case FILE_MMAP:
+               return "mmap";
+       default:
+               return "unknown";
+       }
+}
 
-bool test_cachestat_shmem(void)
+
+bool run_cachestat_test(enum file_type type)
 {
        size_t PS = sysconf(_SC_PAGESIZE);
        size_t filesize = PS * 512 * 2; /* 2 2MB huge pages */
@@ -212,27 +229,50 @@ bool test_cachestat_shmem(void)
        char *filename = "tmpshmcstat";
        struct cachestat cs;
        bool ret = true;
+       int fd;
        unsigned long num_pages = compute_len / PS;
-       int fd = shm_open(filename, O_CREAT | O_RDWR, 0600);
+       if (type == FILE_SHMEM)
+               fd = shm_open(filename, O_CREAT | O_RDWR, 0600);
+       else
+               fd = open(filename, O_RDWR | O_CREAT | O_TRUNC, 0666);
 
        if (fd < 0) {
-               ksft_print_msg("Unable to create shmem file.\n");
+               ksft_print_msg("Unable to create %s file.\n",
+                               file_type_str(type));
                ret = false;
                goto out;
        }
 
        if (ftruncate(fd, filesize)) {
-               ksft_print_msg("Unable to truncate shmem file.\n");
+               ksft_print_msg("Unable to truncate %s file.\n",file_type_str(type));
                ret = false;
                goto close_fd;
        }
+       switch (type) {
+       case FILE_SHMEM:
+               if (!write_exactly(fd, filesize)) {
+                       ksft_print_msg("Unable to write to file.\n");
+                       ret = false;
+                       goto close_fd;
+               }
+               break;
+       case FILE_MMAP:
+               char *map = mmap(NULL, filesize, PROT_READ | PROT_WRITE,
+                                MAP_SHARED, fd, 0);
 
-       if (!write_exactly(fd, filesize)) {
-               ksft_print_msg("Unable to write to shmem file.\n");
+               if (map == MAP_FAILED) {
+                       ksft_print_msg("mmap failed.\n");
+                       ret = false;
+                       goto close_fd;
+               }
+               for (int i = 0; i < filesize; i++)
+                       map[i] = 'A';
+               break;
+       default:
+               ksft_print_msg("Unsupported file type.\n");
                ret = false;
                goto close_fd;
        }
-
        syscall_ret = syscall(__NR_cachestat, fd, &cs_range, &cs, 0);
 
        if (syscall_ret) {
@@ -308,12 +348,18 @@ int main(void)
                break;
        }
 
-       if (test_cachestat_shmem())
+       if (run_cachestat_test(FILE_SHMEM))
                ksft_test_result_pass("cachestat works with a shmem file\n");
        else {
                ksft_test_result_fail("cachestat fails with a shmem file\n");
                ret = 1;
        }
 
+       if (run_cachestat_test(FILE_MMAP))
+               ksft_test_result_pass("cachestat works with a mmap file\n");
+       else {
+               ksft_test_result_fail("cachestat fails with a mmap file\n");
+               ret = 1;
+       }
        return ret;
 }