On Wed, Sep 03, 2025 at 08:54:05AM -0700, Darrick J. Wong wrote:
> On Wed, Sep 03, 2025 at 05:48:46PM +0200, Miklos Szeredi wrote:
> > On Tue, 26 Aug 2025 at 20:52, Darrick J. Wong <djwong@xxxxxxxxxx> wrote:
> >
> > > Hrmm. I was thinking that it would be very nice to have
> > > fuse_request_{send,end} bracket the start and end of a fuse request,
> > > even if we kill it immediately.
> >
> > I'm fine with that, and would possibly simplify some code that checks
> > for an error and calls ->end manually. But that makes it a
> > non-trivial change unfortunately.
>
> Yes, and then you have to poke the idr structure for a request id even
> if that caller already knows that the connection's dead. That seems
> like a waste of cycles, but OTOH maybe we just don't care?
>
> (Though I suppose seeing more than one request id of zero in the trace
> output implies very strongly that the connection is really dead)
Well.... given the fuse_iqueue::reqctr usage, the first request gets a
unique id of 2 and increments by two thereafter. So it's a pretty safe
bet that unique==0 means the request isn't actually being sent, or that
your very lucky in that your fuse server has been running for a /very/
long time.
I think I just won't call trace_fuse_request_send for requests that are
immediately ended; and I'll refactor the req->in.h.unique assignment
into a helper so that virtiofs and friends can call the helper and get
the tracepoint automatically.
For example, fuse_dev_queue_req now becomes:
static inline void fuse_request_assign_unique_locked(struct fuse_iqueue *fiq,
struct fuse_req *req)
{
if (req->in.h.opcode != FUSE_NOTIFY_REPLY)
req->in.h.unique = fuse_get_unique_locked(fiq);
/* tracepoint captures in.h.unique and in.h.len */
trace_fuse_request_send(req);
}
static void fuse_dev_queue_req(struct fuse_iqueue *fiq, struct fuse_req *req)
{
spin_lock(&fiq->lock);
if (fiq->connected) {
fuse_request_assign_unique_locked(fiq, req);
list_add_tail(&req->list, &fiq->pending);
fuse_dev_wake_and_unlock(fiq);
} else {
spin_unlock(&fiq->lock);
req->out.h.error = -ENOTCONN;
clear_bit(FR_PENDING, &req->flags);
fuse_request_end(req);
}
}
--D
