[LTP] [PATCH v5] syscalls/readahead02: test readahead using posix_fadvise()

[Amir Goldstein <amir73il@gmail.com>]

The call to posix_fadvise(POSIX_FADV_WILLNEED) should have the same
effect as the call to readahead() syscall.

Repeat the test cases for local file and overlayfs file with
posix_fadvise().

Signed-off-by: Amir Goldstein <amir73il@gmail.com>
---

 .../kernel/syscalls/readahead/readahead02.c   | 61 ++++++++++++++-----
 1 file changed, 45 insertions(+), 16 deletions(-)

diff --git a/testcases/kernel/syscalls/readahead/readahead02.c b/testcases/kernel/syscalls/readahead/readahead02.c
index de12ba114..d74753dcf 100644
--- a/testcases/kernel/syscalls/readahead/readahead02.c
+++ b/testcases/kernel/syscalls/readahead/readahead02.c
@@ -58,15 +58,34 @@ static struct tst_option options[] = {
 	{NULL, NULL, NULL}
 };
 
+static int libc_readahead(int fd, off_t offset, size_t len)
+{
+	return readahead(fd, offset, len);
+}
+
+static int fadvise_willneed(int fd, off_t offset, size_t len)
+{
+	/* Should have the same effect as readahead() syscall */
+	errno = posix_fadvise(fd, offset, len, POSIX_FADV_WILLNEED);
+	/* posix_fadvise returns error number (not in errno) */
+	return errno ? -1 : 0;
+}
+
 static struct tcase {
 	const char *tname;
 	int use_overlay;
+	int use_fadvise;
+	/* Use either readahead() syscall or POSIX_FADV_WILLNEED */
+	int (*readahead)(int, off_t, size_t);
 } tcases[] = {
-	{ "readahead on file", 0 },
-	{ "readahead on overlayfs file", 1 },
+	{ "readahead on file", 0, 0, libc_readahead },
+	{ "readahead on overlayfs file", 1, 0, libc_readahead },
+	{ "POSIX_FADV_WILLNEED on file", 0, 1, fadvise_willneed },
+	{ "POSIX_FADV_WILLNEED on overlayfs file", 1, 1, fadvise_willneed },
 };
 
 static int readahead_supported = 1;
+static int fadvise_supported = 1;
 
 static int has_file(const char *fname, int required)
 {
@@ -126,7 +145,6 @@ static void create_testfile(int use_overlay)
 	free(tmp);
 }
 
-
 /* read_testfile - mmap testfile and read every page.
  * This functions measures how many I/O and time it takes to fully
  * read contents of test file.
@@ -138,7 +156,8 @@ static void create_testfile(int use_overlay)
  * @usec: returns how many microsecond it took to go over fsize bytes
  * @cached: returns cached kB from /proc/meminfo
  */
-static int read_testfile(int do_readahead, const char *fname, size_t fsize,
+static int read_testfile(struct tcase *tc, int do_readahead,
+			 const char *fname, size_t fsize,
 			 unsigned long *read_bytes, long long *usec,
 			 unsigned long *cached)
 {
@@ -154,7 +173,7 @@ static int read_testfile(int do_readahead, const char *fname, size_t fsize,
 	if (do_readahead) {
 		cached_start = get_cached_size();
 		do {
-			TEST(readahead(fd, offset, fsize - offset));
+			TEST(tc->readahead(fd, offset, fsize - offset));
 			if (TST_RET != 0) {
 				SAFE_CLOSE(fd);
 				return TST_ERR;
@@ -233,7 +252,8 @@ static void test_readahead(unsigned int n)
 	create_testfile(tc->use_overlay);
 
 	/* find out how much can cache hold if we read whole file */
-	read_testfile(0, testfile, testfile_size, &read_bytes, &usec, &cached);
+	read_testfile(tc, 0, testfile, testfile_size, &read_bytes, &usec,
+		      &cached);
 	cached_high = get_cached_size();
 	sync();
 	drop_caches();
@@ -241,7 +261,8 @@ static void test_readahead(unsigned int n)
 	cached_max = MAX(cached_max, cached_high - cached_low);
 
 	tst_res(TINFO, "read_testfile(0)");
-	read_testfile(0, testfile, testfile_size, &read_bytes, &usec, &cached);
+	read_testfile(tc, 0, testfile, testfile_size, &read_bytes, &usec,
+		      &cached);
 	if (cached > cached_low)
 		cached = cached - cached_low;
 	else
@@ -251,20 +272,28 @@ static void test_readahead(unsigned int n)
 	drop_caches();
 	cached_low = get_cached_size();
 	tst_res(TINFO, "read_testfile(1)");
-	ret = read_testfile(1, testfile, testfile_size, &read_bytes_ra,
+	ret = read_testfile(tc, 1, testfile, testfile_size, &read_bytes_ra,
 		            &usec_ra, &cached_ra);
 
-	if (ret == EINVAL &&
-	    (!tc->use_overlay || !readahead_supported)) {
-		readahead_supported = 0;
-		tst_res(TCONF, "readahead not supported on %s",
-			tst_device->fs_type);
-		return;
+	if (ret == EINVAL) {
+		if (tc->use_fadvise &&
+		    (!tc->use_overlay || !fadvise_supported)) {
+			fadvise_supported = 0;
+			tst_res(TCONF, "CONFIG_ADVISE_SYSCALLS not configured "
+				"in kernel?");
+			return;
+		} else if (!tc->use_overlay || !readahead_supported) {
+			readahead_supported = 0;
+			tst_res(TCONF, "readahead not supported on %s",
+				tst_device->fs_type);
+			return;
+		}
 	}
 
 	if (ret) {
-		tst_res(TFAIL | TTERRNO, "readahead failed on %s%s",
-			tc->use_overlay ? "overlayfs on " : "",
+		tst_res(TFAIL | TTERRNO, "%s failed on %s",
+			tc->use_fadvise ? "fadvise" : "readahead",
+			tc->use_overlay ? "overlayfs" :
 			tst_device->fs_type);
 		return;
 	}
-- 
2.17.1