selftests/bpf: Fix intermittent failures in file_reader test

file_reader/on_open_expect_fault intermittently fails when test_progs
runs tests in parallel, because it expects a page fault on first read.
Another file_reader test running concurrently may have already pulled
the same pages into the page cache, eliminating the fault and causing a
spurious failure.

Make file_reader/on_open_expect_fault read from a file region that does
not overlap with other file_reader tests, so the initial access still
faults even under parallel execution.

Signed-off-by: Mykyta Yatsenko <yatsenko@meta.com>
Acked-by: Ihor Solodrai <ihor.solodrai@linux.dev>
Link: https://lore.kernel.org/r/20251029195907.858217-1-mykyta.yatsenko5@gmail.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>

diff --git a/tools/testing/selftests/bpf/prog_tests/file_reader.c b/tools/testing/selftests/bpf/prog_tests/file_reader.c
index 2a034d43b73e0a65ffce59e55a283830788880c3..5cde32b35da4475207251e7c5b6121a6f9e2331b 100644 (file)
--- a/tools/testing/selftests/bpf/prog_tests/file_reader.c
+++ b/tools/testing/selftests/bpf/prog_tests/file_reader.c
@@ -52,7 +52,11 @@ static int initialize_file_contents(void)
        /* page-align base file address */
        addr = (void *)((unsigned long)addr & ~(page_sz - 1));
 
-       for (off = 0; off < sizeof(file_contents); off += page_sz) {
+       /*
+        * Page out range 0..512K, use 0..256K for positive tests and
+        * 256K..512K for negative tests expecting page faults
+        */
+       for (off = 0; off < sizeof(file_contents) * 2; off += page_sz) {
                if (!ASSERT_OK(madvise(addr + off, page_sz, MADV_PAGEOUT),
                               "madvise pageout"))
                        return errno;

diff --git a/tools/testing/selftests/bpf/progs/file_reader.c b/tools/testing/selftests/bpf/progs/file_reader.c
index 2585f83b0ce5d9cda7907bae850053a1f6982bbb..166c3ac6957df41de411e4b0bd22825949ecbe70 100644 (file)
--- a/tools/testing/selftests/bpf/progs/file_reader.c
+++ b/tools/testing/selftests/bpf/progs/file_reader.c
@@ -49,7 +49,7 @@ int on_open_expect_fault(void *c)
        if (bpf_dynptr_from_file(file, 0, &dynptr))
                goto out;
 
-       local_err = bpf_dynptr_read(tmp_buf, user_buf_sz, &dynptr, 0, 0);
+       local_err = bpf_dynptr_read(tmp_buf, user_buf_sz, &dynptr, user_buf_sz, 0);
        if (local_err == -EFAULT) { /* Expect page fault */
                local_err = 0;
                run_success = 1;