[PATCH 2/2] erofs-utils: mount: fix ioctl-based NBD disconnect behavior

[Gao Xiang]

Hi Yifan,

On 2025/12/27 19:39, Yifan Zhao wrote:
> Currently erofsmount_startnbd() doesn't ignore SIGPIPE, causing
> erofsmount_nbd_loopfn() to be killed abruptly without clean up during
> disconnect. Moreover, -EPIPE from NBD socket I/O is expected while
> disconnecting, and erofsmount_startnbd() treats it as error, leading to
> redundant print:
> ```
> <E> erofs: NBD worker failed with [Error 32] Broken pipe
> ```
> 
> Signed-off-by: Yifan Zhao <zhaoyifan28 at huawei.com>
> ---
>   mount/main.c | 13 +++++++++----
>   1 file changed, 9 insertions(+), 4 deletions(-)
> 
> diff --git a/mount/main.c b/mount/main.c
> index 5ba2e0a..965b0b8 100644
> --- a/mount/main.c
> +++ b/mount/main.c
> @@ -621,11 +621,8 @@ static void *erofsmount_nbd_loopfn(void *arg)
>   		off_t pos;
>   
>   		err = erofs_nbd_get_request(ctx->sk.fd, &rq);
> -		if (err < 0) {
> -			if (err == -EPIPE)
> -				err = 0;
> +		if (err < 0)
>   			break;
> -		}
>   
>   		if (rq.type != EROFS_NBD_CMD_READ) {
>   			err = erofs_nbd_send_reply_header(ctx->sk.fd,
> @@ -653,6 +650,8 @@ static void *erofsmount_nbd_loopfn(void *arg)
>   out:
>   	erofs_io_close(&ctx->vd);
>   	erofs_io_close(&ctx->sk);
> +	if (err == -EPIPE)
> +		err = 0;
>   	return (void *)(uintptr_t)err;
>   }
>   
> @@ -663,6 +662,12 @@ static int erofsmount_startnbd(int nbdfd, struct erofs_nbd_source *source)
>   	pthread_t th;
>   	int err, err2;
>   
> +	/* Otherwise, NBD disconnect sends SIGPIPE, skipping cleanup */
> +	if (signal(SIGPIPE, SIG_IGN) == SIG_ERR) {
> +		err = -errno;
> +		goto out_closefd;
> +	}

Can we register a signal handler for SIGPIPE instead, and setup
a disconnected variable for erofsmount_nbd_loopfn() to notice
for example too (in case of unnecessary erofs_nbd_get_request()).

Thanks,
Gao Xiang

> +
>   	if (source->type == EROFSNBD_SOURCE_OCI) {
>   		if (source->ocicfg.tarindex_path || source->ocicfg.zinfo_path) {
>   			err = erofsmount_tarindex_open(&ctx.vd, &source->ocicfg,