[PATCH v10 14/17] fuse: Allow to queue bg requests through io-uring

Bernd Schubert
2025-01-20T01:29:23Z

This prepares queueing and sending background requests through
io-uring.

Signed-off-by: Bernd Schubert <bschubert@ddn.com>
Reviewed-by: Pavel Begunkov <asml.silence@gmail.com> # io_uring
---
fs/fuse/dev.c | 26 +++++++++++++-
fs/fuse/dev_uring.c | 98 +++++++++++++++++++++++++++++++++++++++++++++++++++
fs/fuse/dev_uring_i.h | 12 +++++++
3 files changed, 135 insertions(+), 1 deletion(-)

diff --git a/fs/fuse/dev.c b/fs/fuse/dev.c
index ecf2f805f456222fda02598397beba41fc356460..1b593b23f7b8c319ec38c7e726dabf516965500e 100644
--- a/fs/fuse/dev.c
+++ b/fs/fuse/dev.c
@@ -568,7 +568,25 @@ ssize_t __fuse_simple_request(struct mnt_idmap *idmap,
return ret;
}

-static bool fuse_request_queue_background(struct fuse_req *req)
+#ifdef CONFIG_FUSE_IO_URING
+static bool fuse_request_queue_background_uring(struct fuse_conn *fc,
+ struct fuse_req *req)
+{
+ struct fuse_iqueue *fiq = &fc->iq;
+
+ req->in.h.unique = fuse_get_unique(fiq);
+ req->in.h.len = sizeof(struct fuse_in_header) +
+ fuse_len_args(req->args->in_numargs,
+ (struct fuse_arg *) req->args->in_args);
+
+ return fuse_uring_queue_bq_req(req);
+}
+#endif
+
+/*
+ * @return true if queued
+ */
+static int fuse_request_queue_background(struct fuse_req *req)
{
struct fuse_mount *fm = req->fm;
struct fuse_conn *fc = fm->fc;
@@ -580,6 +598,12 @@ static bool fuse_request_queue_background(struct fuse_req *req)
atomic_inc(&fc->num_waiting);
}
__set_bit(FR_ISREPLY, &req->flags);
+
+#ifdef CONFIG_FUSE_IO_URING
+ if (fuse_uring_ready(fc))
+ return fuse_request_queue_background_uring(fc, req);
+#endif
+
spin_lock(&fc->bg_lock);
if (likely(fc->connected)) {
fc->num_background++;
diff --git a/fs/fuse/dev_uring.c b/fs/fuse/dev_uring.c
index c222d402a7e0eaf4e1898bb3115b10cff1e34165..859e53893eeb5544d57dd961da0e99e7b3d5d9a9 100644
--- a/fs/fuse/dev_uring.c
+++ b/fs/fuse/dev_uring.c
@@ -47,9 +47,51 @@ static struct fuse_ring_ent *uring_cmd_to_ring_ent(struct io_uring_cmd *cmd)
return pdu->ent;
}

+static void fuse_uring_flush_bg(struct fuse_ring_queue *queue)
+{
+ struct fuse_ring *ring = queue->ring;
+ struct fuse_conn *fc = ring->fc;
+
+ lockdep_assert_held(&queue->lock);
+ lockdep_assert_held(&fc->bg_lock);
+
+ /*
+ * Allow one bg request per queue, ignoring global fc limits.
+ * This prevents a single queue from consuming all resources and
+ * eliminates the need for remote queue wake-ups when global
+ * limits are met but this queue has no more waiting requests.
+ */
+ while ((fc->active_background < fc->max_background ||
+ !queue->active_background) &&
+ (!list_empty(&queue->fuse_req_bg_queue))) {
+ struct fuse_req *req;
+
+ req = list_first_entry(&queue->fuse_req_bg_queue,
+ struct fuse_req, list);
+ fc->active_background++;
+ queue->active_background++;
+
+ list_move_tail(&req->list, &queue->fuse_req_queue);
+ }
+}
+
static void fuse_uring_req_end(struct fuse_ring_ent *ent, int error)
{
+ struct fuse_ring_queue *queue = ent->queue;
struct fuse_req *req = ent->fuse_req;
+ struct fuse_ring *ring = queue->ring;
+ struct fuse_conn *fc = ring->fc;
+
+ lockdep_assert_not_held(&queue->lock);
+ spin_lock(&queue->lock);
+ if (test_bit(FR_BACKGROUND, &req->flags)) {
+ queue->active_background--;
+ spin_lock(&fc->bg_lock);
+ fuse_uring_flush_bg(queue);
+ spin_unlock(&fc->bg_lock);
+ }
+
+ spin_unlock(&queue->lock);

if (error)
req->out.h.error = error;
@@ -79,6 +121,7 @@ void fuse_uring_abort_end_requests(struct fuse_ring *ring)
{
int qid;
struct fuse_ring_queue *queue;
+ struct fuse_conn *fc = ring->fc;

for (qid = 0; qid < ring->nr_queues; qid++) {
queue = READ_ONCE(ring->queues[qid]);
@@ -86,6 +129,13 @@ void fuse_uring_abort_end_requests(struct fuse_ring *ring)
continue;

queue->stopped = true;
+
+ WARN_ON_ONCE(ring->fc->max_background != UINT_MAX);
+ spin_lock(&queue->lock);
+ spin_lock(&fc->bg_lock);
+ fuse_uring_flush_bg(queue);
+ spin_unlock(&fc->bg_lock);
+ spin_unlock(&queue->lock);
fuse_uring_abort_end_queue_requests(queue);
}
}
@@ -191,6 +241,7 @@ static struct fuse_ring_queue *fuse_uring_create_queue(struct fuse_ring *ring,
INIT_LIST_HEAD(&queue->ent_w_req_queue);
INIT_LIST_HEAD(&queue->ent_in_userspace);
INIT_LIST_HEAD(&queue->fuse_req_queue);
+ INIT_LIST_HEAD(&queue->fuse_req_bg_queue);

queue->fpq.processing = pq;
fuse_pqueue_init(&queue->fpq);
@@ -1139,6 +1190,53 @@ void fuse_uring_queue_fuse_req(struct fuse_iqueue *fiq, struct fuse_req *req)
fuse_request_end(req);
}

+bool fuse_uring_queue_bq_req(struct fuse_req *req)
+{
+ struct fuse_conn *fc = req->fm->fc;
+ struct fuse_ring *ring = fc->ring;
+ struct fuse_ring_queue *queue;
+ struct fuse_ring_ent *ent = NULL;
+
+ queue = fuse_uring_task_to_queue(ring);
+ if (!queue)
+ return false;
+
+ spin_lock(&queue->lock);
+ if (unlikely(queue->stopped)) {
+ spin_unlock(&queue->lock);
+ return false;
+ }
+
+ list_add_tail(&req->list, &queue->fuse_req_bg_queue);
+
+ ent = list_first_entry_or_null(&queue->ent_avail_queue,
+ struct fuse_ring_ent, list);
+ spin_lock(&fc->bg_lock);
+ fc->num_background++;
+ if (fc->num_background == fc->max_background)
+ fc->blocked = 1;
+ fuse_uring_flush_bg(queue);
+ spin_unlock(&fc->bg_lock);
+
+ /*
+ * Due to bg_queue flush limits there might be other bg requests
+ * in the queue that need to be handled first. Or no further req
+ * might be available.
+ */
+ req = list_first_entry_or_null(&queue->fuse_req_queue, struct fuse_req,
+ list);
+ if (ent && req) {
+ fuse_uring_add_req_to_ring_ent(ent, req);
+ spin_unlock(&queue->lock);
+
+ fuse_uring_dispatch_ent(ent);
+ } else {
+ spin_unlock(&queue->lock);
+ }
+
+ return true;
+}
+
static const struct fuse_iqueue_ops fuse_io_uring_ops = {
/* should be send over io-uring as enhancement */
.send_forget = fuse_dev_queue_forget,
diff --git a/fs/fuse/dev_uring_i.h b/fs/fuse/dev_uring_i.h
index 0517a6eafc9173475d34445c42a88606ceda2e0f..0182be61778b26a94bda2607289a7b668df6362f 100644
--- a/fs/fuse/dev_uring_i.h
+++ b/fs/fuse/dev_uring_i.h
@@ -82,8 +82,13 @@ struct fuse_ring_queue {
/* fuse requests waiting for an entry slot */
struct list_head fuse_req_queue;

+ /* background fuse requests */
+ struct list_head fuse_req_bg_queue;
+
struct fuse_pqueue fpq;

+ unsigned int active_background;
+
bool stopped;
};

@@ -127,6 +132,7 @@ void fuse_uring_stop_queues(struct fuse_ring *ring);
void fuse_uring_abort_end_requests(struct fuse_ring *ring);
int fuse_uring_cmd(struct io_uring_cmd *cmd, unsigned int issue_flags);
void fuse_uring_queue_fuse_req(struct fuse_iqueue *fiq, struct fuse_req *req);
+bool fuse_uring_queue_bq_req(struct fuse_req *req);

static inline void fuse_uring_abort(struct fuse_conn *fc)
{
@@ -179,6 +185,12 @@ static inline void fuse_uring_abort(struct fuse_conn *fc)
static inline void fuse_uring_wait_stopped_queues(struct fuse_conn *fc)
{
}
+
+static inline bool fuse_uring_ready(struct fuse_conn *fc)
+{
+ return false;
+}
+
#endif /* CONFIG_FUSE_IO_URING */

#endif /* _FS_FUSE_DEV_URING_I_H */

--
2.43.0