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AJvYcCWGiprGxC8lOvRXqFNjfHgRcuLVaVAvExEv+jihEPbYBv7oHoey69f4Z+Zuj2CsRPgZdWYs7z/goA==@vger.kernel.org, AJvYcCXkHJAa8k4qX0a8N68Cw/WKKgngpscIHx/A7JnPD1C+wwwh+aVXMYk3FPQp6t9Kz3UyJb8t2p2IaZeUvlqWWw==@vger.kernel.org X-Gm-Message-State: AOJu0YxzY4aRu2+EuJCeaB+o0RR8L5++IpVYdIpwf1jwpDB6Ceradp/2 KboBugtmvVTFN2auxxiynSFnzLDBs0SfzMh604HPF7K1+35sQenWS6bIlPT4+8YgtYiUDl/QpCg aZbKZqeyXwx7/fpVFBrl9JNIpGjMzVqMN X-Gm-Gg: ASbGncsr5dxuBuloLS0XOEOPW6R+pb76x8XPVWLi08oB4pQWRiipRbmNCk6sTRe1W2z rbG3RlfVMDzn+eOzoYT9cDs5+IN8txtEnFXSyNWMx X-Google-Smtp-Source: AGHT+IEtz6qnJFQydRgoZt9BDxrIcXd621hjoJt5D2aRyoLrhQHUFrdWL2joqrLZ2uViulXH8EgZaRj1wFbtr9JmK3s= X-Received: by 2002:ad4:5aeb:0:b0:6d4:211c:dff0 with SMTP id 6a1803df08f44-6df9b250004mr329367136d6.29.1736808288398; Mon, 13 Jan 2025 14:44:48 -0800 (PST) Precedence: bulk X-Mailing-List: io-uring@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 References: <20250107-fuse-uring-for-6-10-rfc4-v9-0-9c786f9a7a9d@ddn.com> <20250107-fuse-uring-for-6-10-rfc4-v9-10-9c786f9a7a9d@ddn.com> In-Reply-To: <20250107-fuse-uring-for-6-10-rfc4-v9-10-9c786f9a7a9d@ddn.com> From: Joanne Koong Date: Mon, 13 Jan 2025 14:44:37 -0800 X-Gm-Features: AbW1kvZAs7Rq8kYYgqf7-z38ja2OMs0BU-cMCF9k8szotOmmJIiSlr70aoIIQic Message-ID: Subject: Re: [PATCH v9 10/17] fuse: Add io-uring sqe commit and fetch support To: Bernd Schubert Cc: Miklos Szeredi , Jens Axboe , Pavel Begunkov , linux-fsdevel@vger.kernel.org, io-uring@vger.kernel.org, Josef Bacik , Amir Goldstein , Ming Lei , David Wei , bernd@bsbernd.com Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable On Mon, Jan 6, 2025 at 4:25=E2=80=AFPM Bernd Schubert w= rote: > > This adds support for fuse request completion through ring SQEs > (FUSE_URING_CMD_COMMIT_AND_FETCH handling). After committing > the ring entry it becomes available for new fuse requests. > Handling of requests through the ring (SQE/CQE handling) > is complete now. > > Fuse request data are copied through the mmaped ring buffer, > there is no support for any zero copy yet. > > Signed-off-by: Bernd Schubert > --- > fs/fuse/dev_uring.c | 450 ++++++++++++++++++++++++++++++++++++++++++++= ++++++ > fs/fuse/dev_uring_i.h | 12 ++ > fs/fuse/fuse_i.h | 4 + > 3 files changed, 466 insertions(+) > > diff --git a/fs/fuse/dev_uring.c b/fs/fuse/dev_uring.c > index b44ba4033615e01041313c040035b6da6af0ee17..f44e66a7ea577390da87e9ac7= d118a9416898c28 100644 > --- a/fs/fuse/dev_uring.c > +++ b/fs/fuse/dev_uring.c > @@ -26,6 +26,19 @@ bool fuse_uring_enabled(void) > return enable_uring; > } > > +static void fuse_uring_req_end(struct fuse_ring_ent *ring_ent, bool set_= err, > + int error) > +{ > + struct fuse_req *req =3D ring_ent->fuse_req; > + > + if (set_err) > + req->out.h.error =3D error; I think we could get away with not having the "bool set_err" as an argument if we do "if (error)" directly. AFAICT, we can use the value of error directly since it always returns zero on success and any non-zero value is considered an error. > + > + clear_bit(FR_SENT, &req->flags); > + fuse_request_end(ring_ent->fuse_req); > + ring_ent->fuse_req =3D NULL; > +} > + > void fuse_uring_destruct(struct fuse_conn *fc) > { > struct fuse_ring *ring =3D fc->ring; > @@ -41,8 +54,11 @@ void fuse_uring_destruct(struct fuse_conn *fc) > continue; > > WARN_ON(!list_empty(&queue->ent_avail_queue)); > + WARN_ON(!list_empty(&queue->ent_w_req_queue)); > WARN_ON(!list_empty(&queue->ent_commit_queue)); > + WARN_ON(!list_empty(&queue->ent_in_userspace)); > > + kfree(queue->fpq.processing); > kfree(queue); > ring->queues[qid] =3D NULL; > } > @@ -101,20 +117,34 @@ static struct fuse_ring_queue *fuse_uring_create_qu= eue(struct fuse_ring *ring, > { > struct fuse_conn *fc =3D ring->fc; > struct fuse_ring_queue *queue; > + struct list_head *pq; > > queue =3D kzalloc(sizeof(*queue), GFP_KERNEL_ACCOUNT); > if (!queue) > return NULL; > + pq =3D kcalloc(FUSE_PQ_HASH_SIZE, sizeof(struct list_head), GFP_K= ERNEL); > + if (!pq) { > + kfree(queue); > + return NULL; > + } > + > queue->qid =3D qid; > queue->ring =3D ring; > spin_lock_init(&queue->lock); > > INIT_LIST_HEAD(&queue->ent_avail_queue); > INIT_LIST_HEAD(&queue->ent_commit_queue); > + INIT_LIST_HEAD(&queue->ent_w_req_queue); > + INIT_LIST_HEAD(&queue->ent_in_userspace); > + INIT_LIST_HEAD(&queue->fuse_req_queue); > + > + queue->fpq.processing =3D pq; > + fuse_pqueue_init(&queue->fpq); > > spin_lock(&fc->lock); > if (ring->queues[qid]) { > spin_unlock(&fc->lock); > + kfree(queue->fpq.processing); > kfree(queue); > return ring->queues[qid]; > } > @@ -128,6 +158,214 @@ static struct fuse_ring_queue *fuse_uring_create_qu= eue(struct fuse_ring *ring, > return queue; > } > > +/* > + * Checks for errors and stores it into the request > + */ > +static int fuse_uring_out_header_has_err(struct fuse_out_header *oh, > + struct fuse_req *req, > + struct fuse_conn *fc) > +{ > + int err; > + > + err =3D -EINVAL; > + if (oh->unique =3D=3D 0) { > + /* Not supportd through io-uring yet */ > + pr_warn_once("notify through fuse-io-uring not supported\= n"); > + goto seterr; > + } > + > + err =3D -EINVAL; > + if (oh->error <=3D -ERESTARTSYS || oh->error > 0) > + goto seterr; > + > + if (oh->error) { > + err =3D oh->error; > + goto err; > + } > + > + err =3D -ENOENT; > + if ((oh->unique & ~FUSE_INT_REQ_BIT) !=3D req->in.h.unique) { > + pr_warn_ratelimited("unique mismatch, expected: %llu got = %llu\n", > + req->in.h.unique, > + oh->unique & ~FUSE_INT_REQ_BIT); > + goto seterr; > + } > + > + /* > + * Is it an interrupt reply ID? > + * XXX: Not supported through fuse-io-uring yet, it should not ev= en > + * find the request - should not happen. > + */ > + WARN_ON_ONCE(oh->unique & FUSE_INT_REQ_BIT); > + > + return 0; > + > +seterr: > + oh->error =3D err; > +err: > + return err; > +} > + > +static int fuse_uring_copy_from_ring(struct fuse_ring *ring, > + struct fuse_req *req, > + struct fuse_ring_ent *ent) > +{ > + struct fuse_copy_state cs; > + struct fuse_args *args =3D req->args; > + struct iov_iter iter; > + int err, res; > + struct fuse_uring_ent_in_out ring_in_out; > + > + res =3D copy_from_user(&ring_in_out, &ent->headers->ring_ent_in_o= ut, > + sizeof(ring_in_out)); > + if (res) > + return -EFAULT; > + > + err =3D import_ubuf(ITER_SOURCE, ent->payload, ring->max_payload_= sz, > + &iter); > + if (err) > + return err; > + > + fuse_copy_init(&cs, 0, &iter); > + cs.is_uring =3D 1; > + cs.req =3D req; > + > + return fuse_copy_out_args(&cs, args, ring_in_out.payload_sz); > +} > + > + /* > + * Copy data from the req to the ring buffer > + */ > +static int fuse_uring_copy_to_ring(struct fuse_ring *ring, struct fuse_r= eq *req, > + struct fuse_ring_ent *ent) > +{ > + struct fuse_copy_state cs; > + struct fuse_args *args =3D req->args; > + struct fuse_in_arg *in_args =3D args->in_args; > + int num_args =3D args->in_numargs; > + int err, res; > + struct iov_iter iter; > + struct fuse_uring_ent_in_out ent_in_out =3D { > + .flags =3D 0, > + .commit_id =3D ent->commit_id, > + }; > + > + if (WARN_ON(ent_in_out.commit_id =3D=3D 0)) > + return -EINVAL; > + > + err =3D import_ubuf(ITER_DEST, ent->payload, ring->max_payload_sz= , &iter); > + if (err) { > + pr_info_ratelimited("fuse: Import of user buffer failed\n= "); > + return err; > + } > + > + fuse_copy_init(&cs, 1, &iter); > + cs.is_uring =3D 1; > + cs.req =3D req; > + > + if (num_args > 0) { > + /* > + * Expectation is that the first argument is the per op h= eader. > + * Some op code have that as zero. > + */ > + if (args->in_args[0].size > 0) { > + res =3D copy_to_user(&ent->headers->op_in, in_arg= s->value, > + in_args->size); > + err =3D res > 0 ? -EFAULT : res; > + if (err) { > + pr_info_ratelimited( > + "Copying the header failed.\n"); > + return err; > + } > + } > + in_args++; > + num_args--; > + } > + > + /* copy the payload */ > + err =3D fuse_copy_args(&cs, num_args, args->in_pages, > + (struct fuse_arg *)in_args, 0); > + if (err) { > + pr_info_ratelimited("%s fuse_copy_args failed\n", __func_= _); > + return err; > + } > + > + ent_in_out.payload_sz =3D cs.ring.copied_sz; > + res =3D copy_to_user(&ent->headers->ring_ent_in_out, &ent_in_out, > + sizeof(ent_in_out)); > + err =3D res > 0 ? -EFAULT : res; > + if (err) > + return err; > + > + return 0; > +} > + > +static int > +fuse_uring_prepare_send(struct fuse_ring_ent *ring_ent) > +{ > + struct fuse_ring_queue *queue =3D ring_ent->queue; > + struct fuse_ring *ring =3D queue->ring; > + struct fuse_req *req =3D ring_ent->fuse_req; > + int err, res; > + > + err =3D -EIO; > + if (WARN_ON(ring_ent->state !=3D FRRS_FUSE_REQ)) { > + pr_err("qid=3D%d ring-req=3D%p invalid state %d on send\n= ", > + queue->qid, ring_ent, ring_ent->state); > + err =3D -EIO; > + goto err; > + } > + > + /* copy the request */ > + err =3D fuse_uring_copy_to_ring(ring, req, ring_ent); > + if (unlikely(err)) { > + pr_info_ratelimited("Copy to ring failed: %d\n", err); > + goto err; > + } > + > + /* copy fuse_in_header */ > + res =3D copy_to_user(&ring_ent->headers->in_out, &req->in.h, > + sizeof(req->in.h)); > + err =3D res > 0 ? -EFAULT : res; > + if (err) > + goto err; > + > + set_bit(FR_SENT, &req->flags); > + return 0; > + > +err: > + fuse_uring_req_end(ring_ent, true, err); > + return err; > +} > + > +/* > + * Write data to the ring buffer and send the request to userspace, > + * userspace will read it > + * This is comparable with classical read(/dev/fuse) > + */ > +static int fuse_uring_send_next_to_ring(struct fuse_ring_ent *ring_ent, > + unsigned int issue_flags) > +{ > + int err =3D 0; > + struct fuse_ring_queue *queue =3D ring_ent->queue; > + > + err =3D fuse_uring_prepare_send(ring_ent); > + if (err) > + goto err; > + > + spin_lock(&queue->lock); > + ring_ent->state =3D FRRS_USERSPACE; > + list_move(&ring_ent->list, &queue->ent_in_userspace); > + spin_unlock(&queue->lock); > + > + io_uring_cmd_done(ring_ent->cmd, 0, 0, issue_flags); > + ring_ent->cmd =3D NULL; > + return 0; > + > +err: > + return err; > +} > + > /* > * Make a ring entry available for fuse_req assignment > */ > @@ -138,6 +376,210 @@ static void fuse_uring_ent_avail(struct fuse_ring_e= nt *ring_ent, > ring_ent->state =3D FRRS_AVAILABLE; > } > > +/* Used to find the request on SQE commit */ > +static void fuse_uring_add_to_pq(struct fuse_ring_ent *ring_ent, > + struct fuse_req *req) > +{ > + struct fuse_ring_queue *queue =3D ring_ent->queue; > + struct fuse_pqueue *fpq =3D &queue->fpq; > + unsigned int hash; > + > + /* commit_id is the unique id of the request */ > + ring_ent->commit_id =3D req->in.h.unique; > + > + req->ring_entry =3D ring_ent; > + hash =3D fuse_req_hash(ring_ent->commit_id); > + list_move_tail(&req->list, &fpq->processing[hash]); > +} > + > +/* > + * Assign a fuse queue entry to the given entry > + */ > +static void fuse_uring_add_req_to_ring_ent(struct fuse_ring_ent *ring_en= t, > + struct fuse_req *req) > +{ > + struct fuse_ring_queue *queue =3D ring_ent->queue; > + > + lockdep_assert_held(&queue->lock); > + > + if (WARN_ON_ONCE(ring_ent->state !=3D FRRS_AVAILABLE && > + ring_ent->state !=3D FRRS_COMMIT)) { > + pr_warn("%s qid=3D%d state=3D%d\n", __func__, ring_ent->q= ueue->qid, > + ring_ent->state); > + } > + list_del_init(&req->list); > + clear_bit(FR_PENDING, &req->flags); > + ring_ent->fuse_req =3D req; > + ring_ent->state =3D FRRS_FUSE_REQ; > + list_move(&ring_ent->list, &queue->ent_w_req_queue); > + fuse_uring_add_to_pq(ring_ent, req); > +} > + > +/* > + * Release the ring entry and fetch the next fuse request if available > + * > + * @return true if a new request has been fetched > + */ > +static bool fuse_uring_ent_assign_req(struct fuse_ring_ent *ring_ent) > + __must_hold(&queue->lock) > +{ > + struct fuse_req *req; > + struct fuse_ring_queue *queue =3D ring_ent->queue; > + struct list_head *req_queue =3D &queue->fuse_req_queue; > + > + lockdep_assert_held(&queue->lock); > + > + /* get and assign the next entry while it is still holding the lo= ck */ > + req =3D list_first_entry_or_null(req_queue, struct fuse_req, list= ); > + if (req) { > + fuse_uring_add_req_to_ring_ent(ring_ent, req); > + return true; > + } > + > + return false; > +} > + > +/* > + * Read data from the ring buffer, which user space has written to > + * This is comparible with handling of classical write(/dev/fuse). > + * Also make the ring request available again for new fuse requests. > + */ > +static void fuse_uring_commit(struct fuse_ring_ent *ring_ent, > + unsigned int issue_flags) > +{ > + struct fuse_ring *ring =3D ring_ent->queue->ring; > + struct fuse_conn *fc =3D ring->fc; > + struct fuse_req *req =3D ring_ent->fuse_req; > + ssize_t err =3D 0; > + bool set_err =3D false; > + > + err =3D copy_from_user(&req->out.h, &ring_ent->headers->in_out, > + sizeof(req->out.h)); > + if (err) { > + req->out.h.error =3D err; > + goto out; > + } > + > + err =3D fuse_uring_out_header_has_err(&req->out.h, req, fc); > + if (err) { > + /* req->out.h.error already set */ > + goto out; > + } > + > + err =3D fuse_uring_copy_from_ring(ring, req, ring_ent); > + if (err) > + set_err =3D true; > + > +out: > + fuse_uring_req_end(ring_ent, set_err, err); > +} > + > +/* > + * Get the next fuse req and send it > + */ > +static void fuse_uring_next_fuse_req(struct fuse_ring_ent *ring_ent, > + struct fuse_ring_queue *queue, > + unsigned int issue_flags) > +{ > + int err; > + bool has_next; > + > +retry: > + spin_lock(&queue->lock); > + fuse_uring_ent_avail(ring_ent, queue); > + has_next =3D fuse_uring_ent_assign_req(ring_ent); > + spin_unlock(&queue->lock); > + > + if (has_next) { > + err =3D fuse_uring_send_next_to_ring(ring_ent, issue_flag= s); > + if (err) > + goto retry; > + } > +} > + > +static int fuse_ring_ent_set_commit(struct fuse_ring_ent *ent) > +{ > + struct fuse_ring_queue *queue =3D ent->queue; > + > + lockdep_assert_held(&queue->lock); > + > + if (WARN_ON_ONCE(ent->state !=3D FRRS_USERSPACE)) > + return -EIO; > + > + ent->state =3D FRRS_COMMIT; > + list_move(&ent->list, &queue->ent_commit_queue); > + > + return 0; > +} > + > +/* FUSE_URING_CMD_COMMIT_AND_FETCH handler */ > +static int fuse_uring_commit_fetch(struct io_uring_cmd *cmd, int issue_f= lags, > + struct fuse_conn *fc) > +{ > + const struct fuse_uring_cmd_req *cmd_req =3D io_uring_sqe_cmd(cmd= ->sqe); > + struct fuse_ring_ent *ring_ent; > + int err; > + struct fuse_ring *ring =3D fc->ring; > + struct fuse_ring_queue *queue; > + uint64_t commit_id =3D READ_ONCE(cmd_req->commit_id); > + unsigned int qid =3D READ_ONCE(cmd_req->qid); > + struct fuse_pqueue *fpq; > + struct fuse_req *req; > + > + err =3D -ENOTCONN; > + if (!ring) > + return err; > + > + if (qid >=3D ring->nr_queues) > + return -EINVAL; > + > + queue =3D ring->queues[qid]; > + if (!queue) > + return err; > + fpq =3D &queue->fpq; > + > + spin_lock(&queue->lock); > + /* Find a request based on the unique ID of the fuse request > + * This should get revised, as it needs a hash calculation and li= st > + * search. And full struct fuse_pqueue is needed (memory overhead= ). > + * As well as the link from req to ring_ent. > + */ imo, the hash calculation and list search seems ok. I can't think of a more optimal way of doing it. Instead of using the full struct fuse_pqueue, I think we could just have the "struct list_head *processing" defined inside "struct fuse_ring_queue" and change fuse_request_find() to take in a list_head. I don't think we need a dedicated spinlock for the list either. We can just reuse queue->lock, as that's (currently) always held already when the processing list is accessed. > + req =3D fuse_request_find(fpq, commit_id); > + err =3D -ENOENT; > + if (!req) { > + pr_info("qid=3D%d commit_id %llu not found\n", queue->qid= , > + commit_id); > + spin_unlock(&queue->lock); > + return err; > + } > + list_del_init(&req->list); > + ring_ent =3D req->ring_entry; > + req->ring_entry =3D NULL; Do we need to set this to NULL, given that the request will be cleaned up later in fuse_uring_req_end() anyways? > + > + err =3D fuse_ring_ent_set_commit(ring_ent); > + if (err !=3D 0) { > + pr_info_ratelimited("qid=3D%d commit_id %llu state %d", > + queue->qid, commit_id, ring_ent->stat= e); > + spin_unlock(&queue->lock); > + return err; > + } > + > + ring_ent->cmd =3D cmd; > + spin_unlock(&queue->lock); > + > + /* without the queue lock, as other locks are taken */ > + fuse_uring_commit(ring_ent, issue_flags); > + > + /* > + * Fetching the next request is absolutely required as queued > + * fuse requests would otherwise not get processed - committing > + * and fetching is done in one step vs legacy fuse, which has sep= arated > + * read (fetch request) and write (commit result). > + */ > + fuse_uring_next_fuse_req(ring_ent, queue, issue_flags); If there's no request ready to read next, then no request will be fetched and this will return. However, as I understand it, once the uring is registered, userspace should only be interacting with the uring via FUSE_IO_URING_CMD_COMMIT_AND_FETCH. However for the case where no request was ready to read, it seems like userspace would have nothing to commit when it wants to fetch the next request? A more general question though: I imagine the most common use case from the server side is waiting / polling until there is a request to fetch. Could we not just do that here in the kernel instead with adding a waitqueue mechanism and having fuse_uring_next_fuse_req() only return when there is a request available? It seems like that would reduce the amount of overhead instead of doing the waiting/checking from the server side? > + return 0; > +} > + > /* > * fuse_uring_req_fetch command handling > */ > @@ -325,6 +767,14 @@ int __maybe_unused fuse_uring_cmd(struct io_uring_cm= d *cmd, > return err; > } > break; > + case FUSE_IO_URING_CMD_COMMIT_AND_FETCH: > + err =3D fuse_uring_commit_fetch(cmd, issue_flags, fc); > + if (err) { > + pr_info_once("FUSE_IO_URING_COMMIT_AND_FETCH fail= ed err=3D%d\n", > + err); > + return err; > + } > + break; > default: > return -EINVAL; > } > diff --git a/fs/fuse/dev_uring_i.h b/fs/fuse/dev_uring_i.h > index 4e46dd65196d26dabc62dada33b17de9aa511c08..80f1c62d4df7f0ca77c4d5179= 068df6ffdbf7d85 100644 > --- a/fs/fuse/dev_uring_i.h > +++ b/fs/fuse/dev_uring_i.h > @@ -20,6 +20,9 @@ enum fuse_ring_req_state { > /* The ring entry is waiting for new fuse requests */ > FRRS_AVAILABLE, > > + /* The ring entry got assigned a fuse req */ > + FRRS_FUSE_REQ, > + > /* The ring entry is in or on the way to user space */ > FRRS_USERSPACE, > }; > @@ -70,7 +73,16 @@ struct fuse_ring_queue { > * entries in the process of being committed or in the process > * to be sent to userspace > */ > + struct list_head ent_w_req_queue; What does the w in this stand for? I find the name ambiguous here. Thanks, Joanne > struct list_head ent_commit_queue; > + > + /* entries in userspace */ > + struct list_head ent_in_userspace; > + > + /* fuse requests waiting for an entry slot */ > + struct list_head fuse_req_queue; > + > + struct fuse_pqueue fpq; > }; > > /** > diff --git a/fs/fuse/fuse_i.h b/fs/fuse/fuse_i.h > index e545b0864dd51e82df61cc39bdf65d3d36a418dc..e71556894bc25808581424ec7= bdd4afeebc81f15 100644 > --- a/fs/fuse/fuse_i.h > +++ b/fs/fuse/fuse_i.h > @@ -438,6 +438,10 @@ struct fuse_req { > > /** fuse_mount this request belongs to */ > struct fuse_mount *fm; > + > +#ifdef CONFIG_FUSE_IO_URING > + void *ring_entry; > +#endif > }; > > struct fuse_iqueue; > > -- > 2.43.0 >