1 files changed, 118 insertions, 0 deletions
diff --git a/linus_stress/linus_stress.c b/linus_stress/linus_stress.c
new file mode 100644
index 0000000..be727b2
--- /dev/null
+++ b/linus_stress/linus_stress.c
@@ -0,0 +1,118 @@
+#include <sys/mman.h>
+#include <sys/fcntl.h>
+#include <unistd.h>
+#include <stdlib.h>
+#include <string.h>
+#include <stdio.h>
+#include <time.h>
+
+#define TARGETSIZE (100 << 20)
+#define CHUNKSIZE (1460)
+#define NRCHUNKS (TARGETSIZE / CHUNKSIZE)
+#define SIZE (NRCHUNKS * CHUNKSIZE)
+
+static void fillmem(void *start, int nr)
+{
+	memset(start, nr, CHUNKSIZE);
+}
+
+#define page_offset(buf, off) (0xfff & ((unsigned)(unsigned long)(buf)+(off)))
+
+static int chunkorder[NRCHUNKS];
+
+static int order(int nr)
+{
+	int i;
+	if (nr < 0 || nr >= NRCHUNKS)
+		return -1;
+	for (i = 0; i < NRCHUNKS; i++)
+		if (chunkorder[i] == nr)
+			return i;
+	return -2;
+}
+
+static void checkmem(void *buf, int nr)
+{
+	unsigned int start = ~0u, end = 0;
+	unsigned char c = nr, *p = buf, differs = 0;
+	int i;
+	for (i = 0; i < CHUNKSIZE; i++) {
+		unsigned char got = *p++;
+		if (got != c) {
+			if (i < start)
+				start = i;
+			if (i > end)
+				end = i;
+			differs = got;
+		}
+	}
+	if (start < end) {
+		printf("Chunk %d corrupted (%u-%u)  (%u-%u)            \n", nr, start, end,
+			page_offset(buf, start), page_offset(buf, end));
+		printf("Expected %u, got %u\n", c, differs);
+		printf("Written as (%d)%d(%d)\n", order(nr-1), order(nr), order(nr+1));
+	}
+}
+
+static char *remap(int fd, char *mapping)
+{
+	if (mapping) {
+		munmap(mapping, SIZE);
+		posix_fadvise(fd, 0, SIZE, POSIX_FADV_DONTNEED);
+	}
+	return mmap(NULL, SIZE, PROT_READ | PROT_WRITE, MAP_SHARED, fd, 0);
+}
+
+int main(int argc, char **argv)
+{
+	char *mapping;
+	int fd, i;
+
+	/*
+	 * Make some random ordering of writing the chunks to the
+	 * memory map..
+	 *
+	 * Start with fully ordered..
+	 */
+	for (i = 0; i < NRCHUNKS; i++)
+		chunkorder[i] = i;
+
+	/* ..and then mix it up randomly */
+	srandom(time(NULL));
+	for (i = 0; i < NRCHUNKS; i++) {
+		int index = (unsigned int) random() % NRCHUNKS;
+		int nr = chunkorder[index];
+		chunkorder[index] = chunkorder[i];
+		chunkorder[i] = nr;
+	}
+
+	fd = open("mapfile", O_RDWR | O_TRUNC | O_CREAT, 0666);
+	if (fd < 0)
+		return -1;
+	if (ftruncate(fd, SIZE) < 0)
+		return -1;
+	mapping = remap(fd, NULL);
+	if (-1 == (int)(long)mapping)
+		return -1;
+
+	for (i = 0; i < NRCHUNKS; i++) {
+		int chunk = chunkorder[i];
+		printf("Writing chunk %d/%d (%d%%)     \r", i, NRCHUNKS, 100*i/NRCHUNKS);
+		fillmem(mapping + chunk * CHUNKSIZE, chunk);
+	}
+	printf("\n");
+
+	/* Unmap, drop, and remap.. */
+	mapping = remap(fd, mapping);
+
+	/* .. and check */
+	for (i = 0; i < NRCHUNKS; i++) {
+		int chunk = i;
+		printf("Checking chunk %d/%d (%d%%)     \r", i, NRCHUNKS, 100*i/NRCHUNKS);
+		checkmem(mapping + chunk * CHUNKSIZE, chunk);
+	}
+	printf("\n");
+	
+	return 0;
+}
+