linux-ext4 - Re: [PATCH 2/2] fuse_trace: move the passthrough-specific code back to passthrough.c

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Message-ID: <CAJnrk1YJP9z2k7zy-NyirMV-Rs8md4WF1MSNJOAfKNaB-Lv_yg@mail.gmail.com>
Date: Fri, 7 Nov 2025 12:55:39 -0800
From: Joanne Koong <joannelkoong@...il.com>
To: "Darrick J. Wong" <djwong@...nel.org>
Cc: miklos@...redi.hu, bernd@...ernd.com, neal@...pa.dev, 
	linux-ext4@...r.kernel.org, linux-fsdevel@...r.kernel.org
Subject: Re: [PATCH 2/2] fuse_trace: move the passthrough-specific code back
 to passthrough.c

On Tue, Oct 28, 2025 at 5:44 PM Darrick J. Wong <djwong@...nel.org> wrote:
>
> From: Darrick J. Wong <djwong@...nel.org>
>
> Add tracepoints for the previous patch.
>
> Signed-off-by: "Darrick J. Wong" <djwong@...nel.org>
> ---
>  fs/fuse/fuse_trace.h |   35 +++++++++++++++++++++++++++++++++++
>  fs/fuse/backing.c    |    5 +++++
>  2 files changed, 40 insertions(+)
>
>
> diff --git a/fs/fuse/fuse_trace.h b/fs/fuse/fuse_trace.h
> index bbe9ddd8c71696..286a0845dc0898 100644
> --- a/fs/fuse/fuse_trace.h
> +++ b/fs/fuse/fuse_trace.h
> @@ -124,6 +124,41 @@ TRACE_EVENT(fuse_request_end,
>                   __entry->unique, __entry->len, __entry->error)
>  );
>
> +#ifdef CONFIG_FUSE_BACKING
> +TRACE_EVENT(fuse_backing_class,
> +       TP_PROTO(const struct fuse_conn *fc, unsigned int idx,
> +                const struct fuse_backing *fb),
> +
> +       TP_ARGS(fc, idx, fb),
> +
> +       TP_STRUCT__entry(
> +               __field(dev_t,                  connection)
> +               __field(unsigned int,           idx)
> +               __field(unsigned long,          ino)
> +       ),
> +
> +       TP_fast_assign(
> +               struct inode *inode = file_inode(fb->file);
> +
> +               __entry->connection     =       fc->dev;
> +               __entry->idx            =       idx;
> +               __entry->ino            =       inode->i_ino;
> +       ),
> +
> +       TP_printk("connection %u idx %u ino 0x%lx",
> +                 __entry->connection,
> +                 __entry->idx,
> +                 __entry->ino)
> +);
> +#define DEFINE_FUSE_BACKING_EVENT(name)                \
> +DEFINE_EVENT(fuse_backing_class, name,         \
> +       TP_PROTO(const struct fuse_conn *fc, unsigned int idx, \
> +                const struct fuse_backing *fb), \
> +       TP_ARGS(fc, idx, fb))
> +DEFINE_FUSE_BACKING_EVENT(fuse_backing_open);
> +DEFINE_FUSE_BACKING_EVENT(fuse_backing_close);
> +#endif /* CONFIG_FUSE_BACKING */
> +
>  #endif /* _TRACE_FUSE_H */
>
>  #undef TRACE_INCLUDE_PATH
> diff --git a/fs/fuse/backing.c b/fs/fuse/backing.c
> index f5efbffd0f456b..b83a3c1b2dff7a 100644
> --- a/fs/fuse/backing.c
> +++ b/fs/fuse/backing.c
> @@ -72,6 +72,7 @@ static int fuse_backing_id_free(int id, void *p, void *data)
>
>         WARN_ON_ONCE(refcount_read(&fb->count) != 1);
>
> +       trace_fuse_backing_close((struct fuse_conn *)data, id, fb);
>         fuse_backing_free(fb);
>         return 0;
>  }
> @@ -145,6 +146,8 @@ int fuse_backing_open(struct fuse_conn *fc, struct fuse_backing_map *map)
>                 fb = NULL;
>                 goto out;
>         }
> +
> +       trace_fuse_backing_open(fc, res, fb);
>  out:
>         pr_debug("%s: fb=0x%p, ret=%i\n", __func__, fb, res);
>
> @@ -194,6 +197,8 @@ int fuse_backing_close(struct fuse_conn *fc, int backing_id)
>         if (err)
>                 goto out_fb;
>
> +       trace_fuse_backing_close(fc, backing_id, fb);
> +

If I'm understanding it correctly, the lines above (added from the
previous patch) are

+ err = ops->may_admin ? ops->may_admin(fc, 0) : 0;
+ if (err)
+       goto out_fb;
+
+ err = ops->may_close ? ops->may_close(fc, fb->file) : 0;
+ if (err)
+        goto out_fb;

and will also do the close in the out_fb goto. So should the
trace_fuse_backing_close() be moved to before the "err =
ops->may_admin..." line so it doesn't get missed in the "if (err)..."
cases?

Thanks,
Joanne

>         err = -ENOENT;
>         test_fb = fuse_backing_id_remove(fc, backing_id);
>         if (!test_fb)
>