On 2025/12/16 15:18, Gao Xiang wrote:
Hi Yifan,
On 2025/12/16 16:05, Yifan Zhao wrote:
If the main process of `erofsmount_nbd()` encounters an error after the
nbd device has been successfully set up, it fails to disconnect it
before exiting, resulting in the subprocess not being cleaned up and
blocked on `ioctl(nbdfd, NBD_DO_IT, 0)`.
Do you have a simple test case (IOWs, how do you test this?)
And is it possible to move the test case to erofs-utils tests?
How to reproduce the issue:
mount.erofs -t erofs.nbd oci.layer=0 <some_non_erofs_image> /mnt/erofs
After the command fails, a leftover mount.erofs process (forked in
erofsmount_nbd()) remains uncleaned.
In fact, I don't have a formal test case—I encountered this while trying
out mount.erofs.
Since this is an end-to-end scenario rather than unit test, would you
recommend adding a regression test for it (and other discovered
mount.erofs issues) in our GitHub CI? (I'm happy to implement it.)
This patch resolves the issue by invoking `erofs_nbd_disconnect()`
before exiting on error.
See below.
Signed-off-by: Yifan Zhao <[email protected]>
---
lib/liberofs_nbd.h | 2 +-
mount/main.c | 8 ++++++++
2 files changed, 9 insertions(+), 1 deletion(-)
diff --git a/lib/liberofs_nbd.h b/lib/liberofs_nbd.h
index 260605a..93daa24 100644
--- a/lib/liberofs_nbd.h
+++ b/lib/liberofs_nbd.h
@@ -28,7 +28,7 @@ struct erofs_nbd_request {
char handle[8]; /* older spelling of cookie */
};
u64 from;
- u32 len;
+ u32 len;
} __packed;
/* 30-day timeout for NBD recovery */
diff --git a/mount/main.c b/mount/main.c
index 758e8f8..a093167 100644
--- a/mount/main.c
+++ b/mount/main.c
@@ -1206,6 +1206,14 @@ static int erofsmount_nbd(struct
erofs_nbd_source *source,
free(id);
}
}
+
+ if (err < 0) {
+ nbdfd = open(nbdpath, O_RDWR);
I'm not sure if it's a best-practice (is it possible
nbdpath can be reused?)
Could we just kill the subprocess instead?
Also ioctl is discouraged and netlink is preferred now.
I will try to give a graceful solution later.
Thanks,
Yifan Zhao
Thanks,
Gao Xiang
+ if (nbdfd > 0) {
+ erofs_nbd_disconnect(nbdfd);
+ close(nbdfd);
+ }
+ }
return err;
}
