Advising the kernel

* f3read
	As long as the kernel honors our advice, f3read doesn't
	ever read data from the system cache instead of reading
	from the memory card, and reading speed measurement  is
	improved.

* f3write
	Progress printout goes smoothly now.

f3read.c

@@ -8,6 +8,8 @@
 #include <string.h>
 #include <stdlib.h>
 #include <errno.h>
+#include <fcntl.h>
+#include <unistd.h>
 #include <err.h>
 
 #include "utils.h"
@@ -44,6 +46,7 @@ static void validate_file(const char *path, const char *filename,
 {
 	uint8_t sector[SECTOR_SIZE], *p, *ptr_end;
 	FILE *f;
+	int fd;
 	int offset_match, error_count;
 	size_t sectors_read;
 	uint64_t offset, expected_offset;
@@ -56,9 +59,21 @@ static void validate_file(const char *path, const char *filename,
 	f = fopen(full_fn, "rb");
 	if (!f)
 		err(errno, "Can't open file %s", full_fn);
+	fd = fileno(f);
+	assert(fd >= 0);
+
+	/* If the kernel follows our advice, f3read won't ever read from cache
+	 * even when testing small memory cards without a remount, and
+	 * we should have better reading speed measurement.
+	 */
+	assert(!fdatasync(fd));
+	assert(!posix_fadvise(fd, 0, 0, POSIX_FADV_DONTNEED));
 
 	/* Obtain initial time. */
 	assert(!gettimeofday(&t1, NULL));
+	/* Help the kernel to help us. */
+	assert(!posix_fadvise(fd, 0, 0, POSIX_FADV_SEQUENTIAL));
+
 	ptr_end = sector + SECTOR_SIZE;
 	sectors_read = fread(sector, SECTOR_SIZE, 1, f);
 	expected_offset = offset_from_filename(filename);

f3write.c

@@ -107,6 +107,8 @@ static int create_and_fill_file(const char *path, int number,
 				fflush(stdout);
 				pt1 = pt2;
 			}
+			/* Help the progress to go smoothly. */
+			assert(!fdatasync(fd));
 		}
 	}
 	assert(!fine || size == 0);