Tahsin Erdogan <tahsin@xxxxxxxxxx> writes:
> An inflight async io could keep the filesystem busy and cause umount
> -EBUSY errors after process exit. When the async io process is killed
> forcibly with SIGKILL, it doesn't get a chance to wait for ios to
> complete.
exit_aio will wait for all outstanding I/O before it returns, so you
shouldn't run into this.
-Jeff
>
> With this patch, instead of killing the children processes, we let them
> exit on their own after the timeout expires.
>
> Signed-off-by: Tahsin Erdogan <tahsin@xxxxxxxxxx>
> ---
> src/aio-dio-regress/aio-dio-invalidate-failure.c | 89 ++++++++++++++----------
> 1 file changed, 54 insertions(+), 35 deletions(-)
>
> diff --git a/src/aio-dio-regress/aio-dio-invalidate-failure.c b/src/aio-dio-regress/aio-dio-invalidate-failure.c
> index 24f3e3c..474a83c 100644
> --- a/src/aio-dio-regress/aio-dio-invalidate-failure.c
> +++ b/src/aio-dio-regress/aio-dio-invalidate-failure.c
> @@ -62,6 +62,26 @@ static unsigned char buf[GINORMOUS] __attribute((aligned (4096)));
> exit(1); \
> } while (0)
>
> +
> +volatile int timeout_reached = 0;
> +
> +static void alarm_handler(int signum)
> +{
> + timeout_reached = 1;
> +}
> +
> +void set_timeout(unsigned int seconds)
> +{
> + struct sigaction sa;
> + memset(&sa, 0, sizeof(sa));
> + sa.sa_handler = alarm_handler;
> + sigemptyset(&sa.sa_mask);
> + if (sigaction(SIGALRM, &sa, NULL) == -1)
> + fail("sigaction: %d\n", errno);
> +
> + alarm(seconds);
> +}
> +
> void spin_dio(int fd)
> {
> io_context_t ctx;
> @@ -70,18 +90,28 @@ void spin_dio(int fd)
> struct io_event event;
> int ret;
>
> + set_timeout(SECONDS);
> +
> io_prep_pwrite(&iocb, fd, buf, GINORMOUS, 0);
>
> ret = io_queue_init(1, &ctx);
> if (ret)
> fail("io_queue_init returned %d", ret);
>
> - while (1) {
> + while (!timeout_reached) {
> ret = io_submit(ctx, 1, iocbs);
> if (ret != 1)
> fail("io_submit returned %d instead of 1", ret);
>
> - ret = io_getevents(ctx, 1, 1, &event, NULL);
> + /*
> + * Retry io_getevents() if it gets interrupted by alarm signal.
> + * We don't want to leave behind uncompleted async io requests
> + * that could cause umount -EBUSY errors.
> + */
> + do {
> + ret = io_getevents(ctx, 1, 1, &event, NULL);
> + } while (ret == -EINTR && timeout_reached);
> +
> if (ret != 1)
> fail("io_getevents returned %d instead of 1", ret);
>
> @@ -99,17 +129,15 @@ void spin_buffered(int fd)
> {
> int ret;
>
> - while (1) {
> + set_timeout(SECONDS);
> +
> + while (!timeout_reached) {
> ret = pwrite(fd, buf, GINORMOUS, 0);
> if (ret != GINORMOUS)
> fail("buffered write returned %d", ret);
> }
> }
>
> -static void alarm_handler(int signum)
> -{
> -}
> -
> int main(int argc, char **argv)
> {
> pid_t buffered_pid;
> @@ -118,7 +146,8 @@ int main(int argc, char **argv)
> int fd;
> int fd2;
> int status;
> - struct sigaction sa;
> + int dio_exit;
> + int buffered_exit;
>
> if (argc != 2)
> fail("only arg should be file name");
> @@ -152,38 +181,28 @@ int main(int argc, char **argv)
> exit(0);
> }
>
> - memset(&sa, 0, sizeof(sa));
> - sa.sa_handler = alarm_handler;
> - sigemptyset(&sa.sa_mask);
> - if (sigaction(SIGALRM, &sa, NULL) == -1)
> - fail("sigaction: %d\n", errno);
>
> - alarm(SECONDS);
> + /* Child processes will exit on their own when timeout expires. */
> + pid = waitpid(dio_pid, &status, 0);
> + printf("dio_pid %d, pid %d, status %#x\n", dio_pid, pid, status);
>
> - pid = wait(&status);
> - if (pid < 0 && errno == EINTR) {
> - /* if we timed out then we're done */
> - kill(buffered_pid, SIGKILL);
> - kill(dio_pid, SIGKILL);
> + dio_exit = (pid == dio_pid && WIFEXITED(status)) ?
> + WEXITSTATUS(status) : 1;
>
> - waitpid(buffered_pid, NULL, 0);
> - waitpid(dio_pid, NULL, 0);
> + pid = waitpid(buffered_pid, &status, 0);
> + printf("buffered_pid %d, pid %d, status %#x\n", buffered_pid, pid, status);
>
> - printf("ran for %d seconds without error, passing\n", SECONDS);
> - exit(0);
> - }
> + buffered_exit = (pid == buffered_pid && WIFEXITED(status)) ?
> + WEXITSTATUS(status) : 1;
>
> - if (pid == dio_pid) {
> - kill(buffered_pid, SIGKILL);
> - waitpid(buffered_pid, NULL, 0);
> - } else {
> - kill(dio_pid, SIGKILL);
> - waitpid(dio_pid, NULL, 0);
> + if (dio_exit || buffered_exit) {
> + /*
> + * pass on the child's pass/fail return code or fail if the
> + * child didn't exit cleanly.
> + */
> + exit(dio_exit || buffered_exit);
> }
>
> - /*
> - * pass on the child's pass/fail return code or fail if the child
> - * didn't exit cleanly.
> - */
> - exit(WIFEXITED(status) ? WEXITSTATUS(status) : 1);
> + printf("ran for %d seconds without error, passing\n", SECONDS);
> + exit(0);
> }
--
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