glusterfs

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#include <sys/file.h>
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#include <stdio.h>
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#include <string.h>
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#include <errno.h>
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#include <sys/types.h>
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#include <sys/stat.h>
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#include <fcntl.h>
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#include <sys/wait.h>
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#ifndef linux
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#define fstat64(fd, st) fstat(fd, st)
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#endif
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int
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run_child(char *filename)
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{
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    int fd = -1, ret = -1;
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    fd = open(filename, O_RDWR);
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    if (fd < 0) {
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        fprintf(stderr, "open failed (%s)\n", strerror(errno));
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        goto out;
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    }
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    ret = flock(fd, LOCK_EX | LOCK_NB);
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    if ((ret == 0) || (errno != EWOULDBLOCK)) {
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        fprintf(stderr,
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                "no locks present, though parent has held "
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                "one\n");
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        ret = -1;
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        goto out;
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    }
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    ret = 0;
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out:
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    return ret;
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}
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int
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main(int argc, char *argv[])
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{
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    int fd = -1, ret = -1, status = 0;
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    char *filename = NULL, *cmd = NULL;
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    struct stat stbuf = {
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        0,
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    };
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    if (argc != 3) {
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        fprintf(stderr,
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                "Usage: %s <filename> "
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                "<gluster-cmd-to-trigger-graph-switch>\n",
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                argv[0]);
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        goto out;
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    }
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    filename = argv[1];
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    cmd = argv[2];
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    fd = open(filename, O_RDWR | O_CREAT, 0);
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    if (fd < 0) {
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        fprintf(stderr, "open (%s) failed (%s)\n", filename, strerror(errno));
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        goto out;
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    }
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    ret = flock(fd, LOCK_EX);
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    if (ret < 0) {
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        fprintf(stderr, "flock failed (%s)\n", strerror(errno));
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        goto out;
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    }
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    system(cmd);
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    /* wait till graph switch completes */
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    ret = fstat64(fd, &stbuf);
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    if (ret < 0) {
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        fprintf(stderr, "fstat64 failure (%s)\n", strerror(errno));
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        goto out;
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    }
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    sleep(10);
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    /* By now old-graph would be disconnected and locks should be cleaned
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     * up if they are not migrated. Check that by trying to acquire a lock
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     * on a new fd opened by another process on same file
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     */
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    ret = fork();
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    if (ret == 0) {
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        ret = run_child(filename);
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    } else {
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        wait(&status);
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        if (WIFEXITED(status)) {
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            ret = WEXITSTATUS(status);
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        } else {
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            ret = 0;
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        }
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    }
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out:
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    return ret;
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}
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