Re: [PATCH v3 1/7] fuse: abort on fatal signal during sync init

[Joanne Koong <joannelkoong@gmail.com>]

On Mon, Mar 16, 2026 at 9:53 AM Miklos Szeredi <mszeredi@redhat.com> wrote:
>
> When sync init is used and the server exits for some reason (error, crash)
> while processing FUSE_INIT, the filesystem creation will hang.  The reason
> is that while all other threads will exit, the mounting thread (or process)
> will keep the device fd open, which will prevent an abort from happening.
>
> This is a regression from the async mount case, where the mount was done
> first, and the FUSE_INIT processing afterwards, in which case there's no
> such recursive syscall keeping the fd open.
>
> Fixes: dfb84c330794 ("fuse: allow synchronous FUSE_INIT")
> Cc: stable@vger.kernel.org # v6.18
> Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>

LGTM but left a comment below

Reviewed-by: Joanne Koong <joannelkoong@gmail.com>

> ---
>  fs/fuse/dev.c    | 6 +++++-
>  fs/fuse/fuse_i.h | 1 +
>  fs/fuse/inode.c  | 1 +
>  3 files changed, 7 insertions(+), 1 deletion(-)
>
> diff --git a/fs/fuse/dev.c b/fs/fuse/dev.c
> index 2c16b94357d5..f0631c48abef 100644
> --- a/fs/fuse/dev.c
> +++ b/fs/fuse/dev.c
> @@ -576,6 +576,9 @@ static void request_wait_answer(struct fuse_req *req)
>                         removed = fuse_remove_pending_req(req, &fiq->lock);
>                 if (removed)
>                         return;
> +
> +               if (req->args->abort_on_kill)
> +                       fuse_abort_conn(fc);

Maybe more straightforward to move this logic a few lines above? eg

@@ -570,6 +570,11 @@ static void request_wait_answer(struct fuse_req *req)
                /* Only fatal signals may interrupt this */
                err = wait_event_killable(req->waitq,
                                        test_bit(FR_FINISHED, &req->flags));
                if (!err)
                        return;

+               if (req->args->abort_on_kill) {
+                       fuse_abort_conn(fc);
+                       return;
+               }

Thanks,
Joanne

>         }
>
>         /*
> @@ -676,7 +679,8 @@ ssize_t __fuse_simple_request(struct mnt_idmap *idmap,
>                         fuse_force_creds(req);
>
>                 __set_bit(FR_WAITING, &req->flags);
> -               __set_bit(FR_FORCE, &req->flags);
> +               if (!args->abort_on_kill)
> +                       __set_bit(FR_FORCE, &req->flags);
>         } else {
>                 WARN_ON(args->nocreds);
>                 req = fuse_get_req(idmap, fm, false);
> diff --git a/fs/fuse/fuse_i.h b/fs/fuse/fuse_i.h
> index 7f16049387d1..23a241f18623 100644
> --- a/fs/fuse/fuse_i.h
> +++ b/fs/fuse/fuse_i.h
> @@ -345,6 +345,7 @@ struct fuse_args {
>         bool is_ext:1;
>         bool is_pinned:1;
>         bool invalidate_vmap:1;
> +       bool abort_on_kill:1;
>         struct fuse_in_arg in_args[4];
>         struct fuse_arg out_args[2];
>         void (*end)(struct fuse_mount *fm, struct fuse_args *args, int error);
> diff --git a/fs/fuse/inode.c b/fs/fuse/inode.c
> index e57b8af06be9..84f78fb89d35 100644
> --- a/fs/fuse/inode.c
> +++ b/fs/fuse/inode.c
> @@ -1551,6 +1551,7 @@ int fuse_send_init(struct fuse_mount *fm)
>         int err;
>
>         if (fm->fc->sync_init) {
> +               ia->args.abort_on_kill = true;
>                 err = fuse_simple_request(fm, &ia->args);
>                 /* Ignore size of init reply */
>                 if (err > 0)
> --
> 2.53.0
>
>