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

[Yifan Zhao]

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;
+	}
+
 	if (source->type == EROFSNBD_SOURCE_OCI) {
 		if (source->ocicfg.tarindex_path || source->ocicfg.zinfo_path) {
 			err = erofsmount_tarindex_open(&ctx.vd, &source->ocicfg,
-- 
2.43.0