On Wed, Aug 20, 2025 at 5:51 PM Darrick J. Wong <djwong@xxxxxxxxxx> wrote:
>
> From: Darrick J. Wong <djwong@xxxxxxxxxx>
>
> The fuse_request_{send,end} tracepoints capture the value of
> req->in.h.unique in the trace output. It would be really nice if we
> could use this to match a request to its response for debugging and
> latency analysis, but the call to trace_fuse_request_send occurs before
> the unique id has been set:
>
> fuse_request_send: connection 8388608 req 0 opcode 1 (FUSE_LOOKUP) len 107
> fuse_request_end: connection 8388608 req 6 len 16 error -2
>
> Move the callsites to trace_fuse_request_send to after the unique id has
> been set, or right before we decide to cancel a request having not set
> one.
>
> Signed-off-by: "Darrick J. Wong" <djwong@xxxxxxxxxx>
> ---
> fs/fuse/dev.c | 6 +++++-
> fs/fuse/dev_uring.c | 8 +++++++-
I think we'll also need to do the equivalent for virtio.
> 2 files changed, 12 insertions(+), 2 deletions(-)
>
>
> diff --git a/fs/fuse/dev.c b/fs/fuse/dev.c
> index 6f2b277973ca7d..05d6e7779387a4 100644
> --- a/fs/fuse/dev.c
> +++ b/fs/fuse/dev.c
> @@ -376,10 +376,15 @@ static void fuse_dev_queue_req(struct fuse_iqueue *fiq, struct fuse_req *req)
> if (fiq->connected) {
> if (req->in.h.opcode != FUSE_NOTIFY_REPLY)
> req->in.h.unique = fuse_get_unique_locked(fiq);
> +
> + /* tracepoint captures in.h.unique */
> + trace_fuse_request_send(req);
> +
> list_add_tail(&req->list, &fiq->pending);
> fuse_dev_wake_and_unlock(fiq);
> } else {
> spin_unlock(&fiq->lock);
> + trace_fuse_request_send(req);
Should this request still show up in the trace even though the request
doesn't actually get sent to the server? imo that makes it
misleading/confusing unless the trace also indicates -ENOTCONN.
> req->out.h.error = -ENOTCONN;
> clear_bit(FR_PENDING, &req->flags);
> fuse_request_end(req);
> @@ -398,7 +403,6 @@ static void fuse_send_one(struct fuse_iqueue *fiq, struct fuse_req *req)
> req->in.h.len = sizeof(struct fuse_in_header) +
> fuse_len_args(req->args->in_numargs,
> (struct fuse_arg *) req->args->in_args);
> - trace_fuse_request_send(req);
> fiq->ops->send_req(fiq, req);
> }
>
> diff --git a/fs/fuse/dev_uring.c b/fs/fuse/dev_uring.c
> index 249b210becb1cc..14f263d4419392 100644
> --- a/fs/fuse/dev_uring.c
> +++ b/fs/fuse/dev_uring.c
> @@ -7,6 +7,7 @@
> #include "fuse_i.h"
> #include "dev_uring_i.h"
> #include "fuse_dev_i.h"
> +#include "fuse_trace.h"
>
> #include <linux/fs.h>
> #include <linux/io_uring/cmd.h>
> @@ -1265,12 +1266,17 @@ void fuse_uring_queue_fuse_req(struct fuse_iqueue *fiq, struct fuse_req *req)
>
> err = -EINVAL;
> queue = fuse_uring_task_to_queue(ring);
> - if (!queue)
> + if (!queue) {
> + trace_fuse_request_send(req);
Same question here.
Thanks,
Joanne
