| /******************************************************************************/ |
| /* Copyright (c) Tim LaBerge <tim.laberge@quantum.com>, 2009 */ |
| /* */ |
| /* 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 */ |
| /* */ |
| /******************************************************************************/ |
| |
| /******************************************************************************/ |
| /* */ |
| /* File: dma_thread_diotest7.c */ |
| /* */ |
| /* Description: The man page for open(2) states the following: */ |
| /* O_DIRECT (Since Linux 2.6.10). Try to minimize cache effects of the I/O */ |
| /* to and from this file. In general this will degrade performance, but it */ |
| /* is useful in special situations, such as when applications do their own */ |
| /* caching. File I/O is done directly to/from user space buffers. The I/O is*/ |
| /* synchronous, that is, at the completion of a read(2) or write(2), data is*/ |
| /* guranteed to have been transferred. Under Linux 2.4 transfer sizes, and */ |
| /* the alignment of user buffer and file offset must all be multiples of */ |
| /* the logical block size of the file system. Under Linux 2.6 alignment to */ |
| /* 512-byte bound-aries suffices. */ |
| /* However, it appears that data corruption may occur when a multithreaded */ |
| /* process reads into a non-page size aligned user buffer. A test program */ |
| /* which reliably reproduces the problem on ext3 and xfs is attached. The */ |
| /* program creates, patterns, reads, and verify a series of files. In the */ |
| /* read phase, a file is opened with O_DIRECT n times, where n is the */ |
| /* number of cpu's. A single buffer large enough to contain the file is */ |
| /* allocated and patterned with data not found in any of the files. The */ |
| /* alignment of the buffer is controlled by a command line option. Each file*/ |
| /* is read in parallel by n threads, where n is the number of cpu's. Thread */ |
| /* 0 reads the first page of data from the file into the first page of the */ |
| /* buffer, thread 1 reads the second page of data in to the second page of */ |
| /* the buffer, and so on. Thread n - 1 reads the remainder of the file into*/ |
| /* the remainder of the buffer. */ |
| /* After a thread reads data into the buffer, it immediately verifies that */ |
| /* the contents of the buffer are correct. If the buffer contains corrupt */ |
| /* data, the thread dumps the data surrounding the corruption and calls */ |
| /* abort(). Otherwise, the thread exits. */ |
| /* Crucially, before the reader threads are dispatched, another thread is */ |
| /* started which calls fork()/msleep() in a loop until all reads are compl- */ |
| /* eted. The child created by fork() does nothing but call exit(0). A comm- */ |
| /* and line option controls whether the buffer is aligned. In the case wh- */ |
| /* ere the buffer is aligned on a page boundary, all is well. In the case */ |
| /* where the buffer is aligned on a page + 512 byte offset, corruption is */ |
| /* seen frequently. */ |
| /* I believe that what is happening is that in the direct IO path, because */ |
| /* the user's buffer is not aligned, some user pages are being mapped twice.*/ |
| /* When a fork() happens in between the calls to map the page, the page will*/ |
| /* be marked as COW. When the second map happens (via get_user_pages()), a */ |
| /* new physical page will be allocated and copied. Thus, there is a race */ |
| /* between the completion of the first read from disk (and write to the user*/ |
| /* page) and get_user_pages() mapping the page for the second time. If the */ |
| /* write does not complete before the page is copied, the user will see */ |
| /* stale data in the first 512 bytes of this page of their buffer. Indeed, */ |
| /* this is corruption most frequently seen. (It's also possible for the race*/ |
| /* to be lost the other way, so that the last 3584 bytes of the page are */ |
| /* stale.) */ |
| /* The attached program (which is a heavily modified version of a program */ |
| /* provided by a customer seeing this problem) reliably reproduces the pro- */ |
| /* blem on any multicore linux machine on both ext3 and xfs, although any */ |
| /* filesystem using the generic blockdev_direct_IO() routine is probably */ |
| /* vulnerable. I've seen a few threads that mention the potential for this */ |
| /* kind of problem, but no definitive solution or workaround (other than */ |
| /* "Don't do that"). */ |
| /* http://marc.info/?l=linux-mm&m=122668235304637&w=2 */ |
| /* */ |
| /* Total Tests: 1 */ |
| /* */ |
| /* Test Name: dma_thread_diotest7 */ |
| /* */ |
| /* Author: Tim LaBerge <tim.laberge@quantum.com> */ |
| /* */ |
| /* History: Reported - Jan 07 2009 - Li Zefan <lizf@cn.fujitsu.com> */ |
| /* Ported - Jan 23 2009 - Subrata <subrata@linux.vnet.ibm.com> */ |
| /* */ |
| /******************************************************************************/ |
| |
| #define _GNU_SOURCE 1 |
| |
| #include <stdio.h> |
| #include <stdlib.h> |
| #include <fcntl.h> |
| #include <unistd.h> |
| #include <memory.h> |
| #include <pthread.h> |
| #include <getopt.h> |
| #include <errno.h> |
| #include <sys/types.h> |
| #include <sys/wait.h> |
| |
| #define FILESIZE (12*1024*1024) |
| #define READSIZE (1024*1024) |
| |
| #define FILENAME "_dma_thread_test_%.04d.tmp" |
| #define FILECOUNT 100 |
| #define MIN_WORKERS 2 |
| #define MAX_WORKERS 256 |
| #define PAGE_SIZE getpagesize() |
| |
| #define true 1 |
| #define false 0 |
| |
| typedef int bool; |
| |
| bool done = false; |
| int workers = 2; |
| |
| #define PATTERN (0xfa) |
| |
| static void |
| usage (void) |
| { |
| fprintf(stderr, "\nUsage: dma_thread [-h | -a <alignment> [ -w <workers>]\n" |
| "\nWith no arguments, generate test files and exit.\n" |
| "-h Display this help and exit.\n" |
| "-a align read buffer to offset <alignment>.\n" |
| "-w number of worker threads, 2 (default) to 256,\n" |
| " defaults to number of cores.\n\n" |
| |
| "Run first with no arguments to generate files.\n" |
| "Then run with -a <alignment> = 512 or 0. \n"); |
| } |
| |
| typedef struct { |
| pthread_t tid; |
| int worker_number; |
| int fd; |
| int offset; |
| int length; |
| int pattern; |
| unsigned char *buffer; |
| } worker_t; |
| |
| void *worker_thread(void * arg) |
| { |
| int bytes_read; |
| int i,k; |
| worker_t *worker = (worker_t *) arg; |
| int offset = worker->offset; |
| int fd = worker->fd; |
| unsigned char *buffer = worker->buffer; |
| int pattern = worker->pattern; |
| int length = worker->length; |
| |
| if (lseek(fd, offset, SEEK_SET) < 0) { |
| fprintf(stderr, "Failed to lseek to %d on fd %d: %s.\n", |
| offset, fd, strerror(errno)); |
| exit(1); |
| } |
| |
| bytes_read = read(fd, buffer, length); |
| if (bytes_read != length) { |
| fprintf(stderr, "read failed on fd %d: bytes_read %d, %s\n", |
| fd, bytes_read, strerror(errno)); |
| exit(1); |
| } |
| |
| /* Corruption check */ |
| for (i = 0; i < length; i++) { |
| if (buffer[i] != pattern) { |
| printf("Bad data at 0x%.06x: %p, \n", i, buffer + i); |
| printf("Data dump starting at 0x%.06x:\n", i - 8); |
| printf("Expect 0x%x followed by 0x%x:\n", |
| pattern, PATTERN); |
| |
| for (k = 0; k < 16; k++) { |
| printf("%02x ", buffer[i - 8 + k]); |
| if (k == 7) { |
| printf("\n"); |
| } |
| } |
| |
| printf("\n"); |
| abort(); |
| } |
| } |
| |
| return 0; |
| } |
| |
| void *fork_thread (void *arg) |
| { |
| pid_t pid; |
| |
| while (!done) { |
| pid = fork(); |
| if (pid == 0) { |
| exit(0); |
| } else if (pid < 0) { |
| fprintf(stderr, "Failed to fork child.\n"); |
| exit(1); |
| } |
| waitpid(pid, NULL, 0 ); |
| usleep(100); |
| } |
| |
| return NULL; |
| |
| } |
| |
| int main(int argc, char *argv[]) |
| { |
| unsigned char *buffer = NULL; |
| char filename[1024]; |
| int fd; |
| bool dowrite = true; |
| pthread_t fork_tid; |
| int c, n, j; |
| worker_t *worker; |
| int align = 0; |
| int offset, rc; |
| |
| workers = sysconf(_SC_NPROCESSORS_ONLN); |
| |
| while ((c = getopt(argc, argv, "a:hw:")) != -1) { |
| switch (c) { |
| case 'a': |
| align = atoi(optarg); |
| if (align < 0 || align > PAGE_SIZE) { |
| printf("Bad alignment %d.\n", align); |
| exit(1); |
| } |
| dowrite = false; |
| break; |
| |
| case 'h': |
| usage(); |
| exit(0); |
| break; |
| |
| case 'w': |
| workers = atoi(optarg); |
| if (workers < MIN_WORKERS || workers > MAX_WORKERS) { |
| fprintf(stderr, "Worker count %d not between " |
| "%d and %d, inclusive.\n", |
| workers, MIN_WORKERS, MAX_WORKERS); |
| usage(); |
| exit(1); |
| } |
| dowrite = false; |
| break; |
| |
| default: |
| usage(); |
| exit(1); |
| } |
| } |
| |
| if (argc > 1 && (optind < argc)) { |
| fprintf(stderr, "Bad command line.\n"); |
| usage(); |
| exit(1); |
| } |
| |
| if (dowrite) { |
| |
| buffer = malloc(FILESIZE); |
| if (buffer == NULL) { |
| fprintf(stderr, "Failed to malloc write buffer.\n"); |
| exit(1); |
| } |
| |
| for (n = 1; n <= FILECOUNT; n++) { |
| sprintf(filename, FILENAME, n); |
| fd = open(filename, O_RDWR|O_CREAT|O_TRUNC, 0666); |
| if (fd < 0) { |
| printf("create failed(%s): %s.\n", filename, strerror(errno)); |
| exit(1); |
| } |
| memset(buffer, n, FILESIZE); |
| printf("Writing file %s.\n", filename); |
| if (write(fd, buffer, FILESIZE) != FILESIZE) { |
| printf("write failed (%s)\n", filename); |
| } |
| |
| close(fd); |
| fd = -1; |
| } |
| |
| free(buffer); |
| buffer = NULL; |
| |
| printf("done\n"); |
| exit(0); |
| } |
| |
| printf("Using %d workers.\n", workers); |
| |
| worker = malloc(workers * sizeof(worker_t)); |
| if (worker == NULL) { |
| fprintf(stderr, "Failed to malloc worker array.\n"); |
| exit(1); |
| } |
| |
| for (j = 0; j < workers; j++) { |
| worker[j].worker_number = j; |
| } |
| |
| printf("Using alignment %d.\n", align); |
| |
| posix_memalign((void *)&buffer, PAGE_SIZE, READSIZE+ align); |
| printf("Read buffer: %p.\n", buffer); |
| for (n = 1; n <= FILECOUNT; n++) { |
| |
| sprintf(filename, FILENAME, n); |
| for (j = 0; j < workers; j++) { |
| if ((worker[j].fd = open(filename, O_RDONLY|O_DIRECT)) < 0) { |
| fprintf(stderr, "Failed to open %s: %s.\n", |
| filename, strerror(errno)); |
| exit(1); |
| } |
| |
| worker[j].pattern = n; |
| } |
| |
| printf("Reading file %d.\n", n); |
| |
| for (offset = 0; offset < FILESIZE; offset += READSIZE) { |
| memset(buffer, PATTERN, READSIZE + align); |
| for (j = 0; j < workers; j++) { |
| worker[j].offset = offset + j * PAGE_SIZE; |
| worker[j].buffer = buffer + align + j * PAGE_SIZE; |
| worker[j].length = PAGE_SIZE; |
| } |
| /* The final worker reads whatever is left over. */ |
| worker[workers - 1].length = READSIZE - PAGE_SIZE * (workers - 1); |
| |
| done = 0; |
| |
| rc = pthread_create(&fork_tid, NULL, fork_thread, NULL); |
| if (rc != 0) { |
| fprintf(stderr, "Can't create fork thread: %s.\n", |
| strerror(rc)); |
| exit(1); |
| } |
| |
| for (j = 0; j < workers; j++) { |
| rc = pthread_create(&worker[j].tid, |
| NULL, |
| worker_thread, |
| worker + j); |
| if (rc != 0) { |
| fprintf(stderr, "Can't create worker thread %d: %s.\n", |
| j, strerror(rc)); |
| exit(1); |
| } |
| } |
| |
| for (j = 0; j < workers; j++) { |
| rc = pthread_join(worker[j].tid, NULL); |
| if (rc != 0) { |
| fprintf(stderr, "Failed to join worker thread %d: %s.\n", |
| j, strerror(rc)); |
| exit(1); |
| } |
| } |
| |
| /* Let the fork thread know it's ok to exit */ |
| done = 1; |
| |
| rc = pthread_join(fork_tid, NULL); |
| if (rc != 0) { |
| fprintf(stderr, "Failed to join fork thread: %s.\n", |
| strerror(rc)); |
| exit(1); |
| } |
| } |
| |
| /* Close the fd's for the next file. */ |
| for (j = 0; j < workers; j++) { |
| close(worker[j].fd); |
| } |
| } |
| |
| return 0; |
| } |