[Devel] Re: STDIN_FILENO during restart

[Oren Laadan]

Hi Suka,

Indeed the use of STDIN_FILENO wasn't too friendly to callers
of the library. However, I think the correct fix is different.
So I fixed that, and added a few other cleanups in an attempt
to ensure that the restart code cleans up properly after being
called (succesfully or unsuccesfully) - including memory leaks,
file decsriptors, and even drop a call to setpgrp(). I pushed
those patches to user-cr.

Thanks,

Oren.


On 12/14/2010 12:50 AM, Sukadev Bhattiprolu wrote:
> Oren
> 
> Is there a reason we hard code STDIN_FILENO during restart in usercr ?
> 
> Or can we simply use the fd passed by the caller of cr_restart() -
> something like in this patch ? 
> 
> Whether it is STDIN_FILENO or another fd, do_sys_restart() holds a reference
> to the 'struct file' and so we should still be able to read the image even
> if close_all_fds() closes the fd. Or is there a subtle reason, we stick to
> STDIN_FILENO ?
> 
> Sukadev
> ---
>  src/lxc/user-cr/restart.c |   35 ++++++++++++++++++++++-------------
>  1 files changed, 22 insertions(+), 13 deletions(-)
> 
> diff --git a/src/lxc/user-cr/restart.c b/src/lxc/user-cr/restart.c
> index 5b22948..944dbf1 100644
> --- a/src/lxc/user-cr/restart.c
> +++ b/src/lxc/user-cr/restart.c
> @@ -169,6 +169,7 @@ static int global_child_status;
>  static int global_child_collected;
>  static int global_sent_sigint;
>  static struct signal_array signal_array[] = INIT_SIGNAL_ARRAY;
> +static int global_input_fd = -1;
> 
>  /*
>   * TODO: Implement an API to let callers choose if/how an interrupt be sent
> @@ -403,15 +404,23 @@ int process_args(struct cr_restart_args *args)
>  	global_ulogfd = args->ulogfd;
>  	global_uerrfd = args->uerrfd;
> 
> +	if (args->infd < 0) {
> +		ckpt_err("Invalid input fd %d\n", args->infd);
> +		exit(1);
> +	}
> +	global_input_fd = args->infd;
> +
> +#if 0
>  	/* input file descriptor (default: stdin) */
>  	if (args->infd >= 0) {
> -		if (dup2(args->infd, STDIN_FILENO) < 0) {
> +		if (dup2(args->infd, global_input_fd) < 0) {
>  			ckpt_perror("dup2 input file");
>  			exit(1);
>  		}
> -		if (args->infd != STDIN_FILENO)
> +		if (args->infd != global_input_fd)
>  			close(args->infd);
>  	}
> +#endif
> 
>  	/* output file descriptor (default: none) */
>  	if (args->klogfd < 0)
> @@ -492,7 +501,7 @@ int cr_restart(struct cr_restart_args *args)
>  		if (args->mnt_pty && ckpt_remount_devpts(&ctx) < 0)
>  			exit(1);
> 
> -		restart(getpid(), STDIN_FILENO, RESTART_TASKSELF, args->klogfd);
> +		restart(getpid(), global_input_fd, RESTART_TASKSELF, args->klogfd);
> 
>  		/* reach here if restart(2) failed ! */
>  		ckpt_perror("restart");
> @@ -926,7 +935,7 @@ static int ckpt_coordinator(struct ckpt_ctx *ctx)
>  	if (ctx->args->keep_lsm)
>  		flags |= RESTART_KEEP_LSM;
> 
> -	ret = restart(root_pid, STDIN_FILENO, flags, ctx->args->klogfd);
> +	ret = restart(root_pid, global_input_fd, flags, ctx->args->klogfd);
> 
>  	if (ret < 0) {
>  		ckpt_perror("restart failed");
> @@ -1658,7 +1667,7 @@ static int ckpt_make_tree(struct ckpt_ctx *ctx, struct task *task)
> 
>  	/* on success this doesn't return */
>  	ckpt_dbg("about to call sys_restart(), flags %#lx\n", flags);
> -	ret = restart(0, STDIN_FILENO, flags, CHECKPOINT_FD_NONE);
> +	ret = restart(0, global_input_fd, flags, CHECKPOINT_FD_NONE);
>  	if (ret < 0)
>  		ckpt_perror("task restore failed");
>  	return ret;
> @@ -1857,8 +1866,8 @@ static int ckpt_fork_feeder(struct ckpt_ctx *ctx)
>  	ctx->pipe_out = ctx->pipe_child[1];
>  	/* feeder pipe */
>  	close(ctx->pipe_feed[1]);
> -	if (ctx->pipe_feed[0] != STDIN_FILENO) {
> -		dup2(ctx->pipe_feed[0], STDIN_FILENO);
> +	if (ctx->pipe_feed[0] != global_input_fd) {
> +		dup2(ctx->pipe_feed[0], global_input_fd);
>  		close(ctx->pipe_feed[0]);
>  	}
> 
> @@ -1878,7 +1887,7 @@ static void ckpt_read_write_blind(struct ckpt_ctx *ctx)
>  	int ret;
> 
>  	while (1) {
> -		ret = read(STDIN_FILENO, ctx->buf, BUFSIZE);
> +		ret = read(global_input_fd, ctx->buf, BUFSIZE);
>  		ckpt_dbg("c/r read input %d\n", ret);
>  		if (ret == 0)
>  			break;
> @@ -1897,7 +1906,7 @@ static void ckpt_read_write_inspect(struct ckpt_ctx *ctx)
>  	int len, ret;
> 
>  	while (1) {
> -		ret = _ckpt_read(STDIN_FILENO, &h, sizeof(h));
> +		ret = _ckpt_read(global_input_fd, &h, sizeof(h));
>  ckpt_dbg("ret %d len %d type %d\n", ret, h.len, h.type);
>  		if (ret == 0)
>  			break;
> @@ -1915,7 +1924,7 @@ ckpt_dbg("ret %d len %d type %d\n", ret, h.len, h.type);
>  		h.len -= sizeof(h);
>  		if (h.type == CKPT_HDR_ERROR) {
>  			len = (h.len > BUFSIZE ? BUFSIZE : h.len);
> -			ret = read(STDIN_FILENO, ctx->buf, len);
> +			ret = read(global_input_fd, ctx->buf, len);
>  			if (ret < 0)
>  				ckpt_abort(ctx, "error record");
>  			errno = EIO;
> @@ -1926,7 +1935,7 @@ ckpt_dbg("ret %d len %d type %d\n", ret, h.len, h.type);
> 
>  		while (h.len) {
>  			len = (h.len > BUFSIZE ? BUFSIZE : h.len);
> -			ret = read(STDIN_FILENO, ctx->buf, len);
> +			ret = read(global_input_fd, ctx->buf, len);
>  			if (ret == 0)
>  				ckpt_abort(ctx, "short record");
>  			if (ret < 0)
> @@ -2163,7 +2172,7 @@ static int ckpt_read_obj(struct ckpt_ctx *ctx,
>  {
>  	int ret;
> 
> -	ret = ckpt_read(STDIN_FILENO, h, sizeof(*h));
> +	ret = ckpt_read(global_input_fd, h, sizeof(*h));
>  	if (ret < 0)
>  		return ret;
>  	if (h->len < sizeof(*h) || h->len > n) {
> @@ -2172,7 +2181,7 @@ static int ckpt_read_obj(struct ckpt_ctx *ctx,
>  	}
>  	if (h->len == sizeof(*h))
>  		return 0;
> -	return ckpt_read(STDIN_FILENO, buf, h->len - sizeof(*h));
> +	return ckpt_read(global_input_fd, buf, h->len - sizeof(*h));
>  }
> 
>  static int ckpt_read_obj_type(struct ckpt_ctx *ctx, void *buf, int n, int type)
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