test extending sub-block AIO writes for races

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+/*
+ * Launch 4 file-extending extending sub-block AIOs and ensure that we
+ * don't see data corruption when they're all complete.
+ *
+ * Copyright (C) 2015 Red Hat, Inc. All Rights reserved.
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA  02111-1307, USA.
+ */
+#include <sys/stat.h>
+#include <sys/types.h>
+#include <errno.h>
+#include <fcntl.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <unistd.h>
+#include <ctype.h>
+
+#include <libaio.h>
+
+#define BUF_SIZE	4096
+#define IO_PATTERN	0xab
+
+void
+dump_buffer(
+	void	*buf,
+	off64_t	offset,
+	ssize_t	len)
+{
+	int	i, j;
+	char	*p;
+	int	new;
+	
+	for (i = 0, p = (char *)buf; i < len; i += 16) {
+		char    *s = p;
+
+		if (i && !memcmp(p, p - 16, 16)) {
+			new = 0;
+		} else {
+			if (i)
+				printf("*\n");
+			new = 1;
+		}
+
+		if (!new) {
+			p += 16;
+			continue;
+		}
+
+		printf("%08llx  ", (unsigned long long)offset + i);
+		for (j = 0; j < 16 && i + j < len; j++, p++)
+			printf("%02x ", *p);
+		printf(" ");
+		for (j = 0; j < 16 && i + j < len; j++, s++) {
+			if (isalnum((int)*s))
+				printf("%c", *s);
+			else
+				printf(".");
+		}
+		printf("\n");
+
+	}
+	printf("%08llx\n", (unsigned long long)offset + i);
+}
+
+int main(int argc, char *argv[])
+{
+	struct io_context *ctx = NULL;
+	struct io_event evs[4];
+	struct iocb iocb1, iocb2, iocb3, iocb4;
+	struct iocb *iocbs[] = { &iocb1, &iocb2, &iocb3, &iocb4 };
+	void *buf;
+	struct stat statbuf;
+	char cmp_buf[BUF_SIZE];
+	int fd, err = 0;
+	off_t eof;
+
+	fd = open(argv[1], O_DIRECT | O_CREAT | O_TRUNC | O_RDWR, 0600);
+	if (fd == -1) {
+		perror("open");
+		return 1;
+	}
+
+	err = posix_memalign(&buf, BUF_SIZE, BUF_SIZE);
+	if (err) {
+		fprintf(stderr, "error %s during %s\n",
+			strerror(err),
+			"posix_memalign");
+		return 1;
+	}
+	memset(cmp_buf, IO_PATTERN, BUF_SIZE);
+
+	err = io_setup(4, &ctx);
+	if (err) {
+		fprintf(stderr, "error %s during %s\n",
+			strerror(err),
+			"io_setup");
+		return 1;
+	}
+
+	eof = 0;
+
+	/* Keep extending until 8MB */
+	while (eof < 8 * 1024 * 1024) {
+		memset(buf, IO_PATTERN, BUF_SIZE);
+
+		fstat(fd, &statbuf);
+		eof = statbuf.st_size;
+
+		/*
+		 * 4 ios, racing to extend EOF, combined they write full BUF_SIZE
+		 */
+		io_prep_pwrite(&iocb1, fd, buf, BUF_SIZE/4, eof + 0 * BUF_SIZE/4);
+		io_prep_pwrite(&iocb2, fd, buf, BUF_SIZE/4, eof + 1 * BUF_SIZE/4);
+		io_prep_pwrite(&iocb3, fd, buf, BUF_SIZE/4, eof + 2 * BUF_SIZE/4);
+		io_prep_pwrite(&iocb4, fd, buf, BUF_SIZE/4, eof + 3 * BUF_SIZE/4);
+	
+		err = io_submit(ctx, 4, iocbs);
+		if (err != 4) {
+			fprintf(stderr, "error %s during %s\n",
+				strerror(err),
+				"io_submit");
+			return 1;
+		}
+
+		err = io_getevents(ctx, 4, 4, evs, NULL);
+		if (err != 4) {
+			fprintf(stderr, "error %s during %s\n",
+				strerror(err),
+				"io_getevents");
+			return 1;
+		}
+
+		/*
+		 * And then read it back.
+		 *
+		 * Using pread to keep it simple, but AIO has the same effect.
+		 *
+		 * eof is the old eof, we just wrote BUF_SIZE more
+		 */
+		if (pread(fd, buf, BUF_SIZE, eof) != BUF_SIZE) {
+			perror("pread");
+			return 1;
+		}
+
+		/*
+		 * We launched 4 AIOs which, stiched together, should write
+		 * a seamless BUF_SIZE worth of IO_PATTERN to the last block
+		 */
+		if (memcmp(buf, cmp_buf, BUF_SIZE)) {
+			printf("corruption while extending from %ld\n", eof);
+			dump_buffer(buf, 0, BUF_SIZE);
+			return 1;
+		}
+	}
+
+	printf("Success, all done.\n");
+	return 0;
+}


test extending sub-block AIO writes for races

Eric Sandeen

Brian Foster

Eric Sandeen

Brian Foster

Eric Sandeen

Brian Foster