Test program

dpwrite.c

#define _GNU_SOURCE

#include <stdio.h>
#include <unistd.h>
#include <stdlib.h>
#include <fcntl.h>
#include <sys/types.h>
#include <string.h>
#include <sys/stat.h>

#define BLOCK_SIZE 524288
#define FILES_LIMIT 2

int main(int argc, char **argv) {
        char *data;
        u_int64_t rc, f_i, w_i, rand_n;
        int64_t fds[FILES_LIMIT];
        char filename[2048];

        rc = 0;
        if (posix_memalign((void **) &data, 512, BLOCK_SIZE)) {
                rc = 2;
                goto err;
        }

        memset(data, 'b', BLOCK_SIZE);

        for (f_i=0; f_i < FILES_LIMIT; f_i++) {
                sprintf(filename, "/var/lib/mysql/xfs/plain_pwrite_%lld.werr", f_i);
                fds[f_i] = open(filename, O_CREAT | O_RDWR | (argc > 1 ? O_DIRECT : 0));
                if (fds[f_i] < 0) {
                        rc = 1;
                        goto err;
                }
        }

        for (w_i=0; w_i<8192; w_i++) {
                int64_t fd, s, off;

                // rand_n = i % FILES_LIMIT;
                rand_n = rand() % FILES_LIMIT;
                fd = fds[rand_n];
                printf("file rand = %llu fd = %lld\n", rand_n, fd);
                off = lseek(fd, 0, SEEK_END);
                s = pwrite(fd, data, BLOCK_SIZE, off);
                printf("wrote %lld bytes, file offset %lld\n", s, off);
                if (s < 0) {
                        rc = 3;
                        goto err;
                }

                s = fsync(fd);
                printf("fsync success %lld\n", s);
                if (s < 0) {
                        rc = 4;
                        goto err;
                }
        }

err:
        free(data);
        for (; f_i; f_i--) {
                close(fds[f_i]);
        }

        return rc;
}