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[87.50.154.159]) by smtp.gmail.com with ESMTPSA id h22-v6sm2410703ljg.24.2018.12.16.23.37.46 (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Sun, 16 Dec 2018 23:37:47 -0800 (PST) Subject: Re: [PATCH 1/3] 9p/net: implement asynchronous rpc To: Dominique Martinet , v9fs-developer@lists.sourceforge.net Cc: Dominique Martinet , netdev@vger.kernel.org, linux-kernel@vger.kernel.org, Eric Van Hensbergen , Latchesar Ionkov , Dmitry Vyukov References: <1544532108-21689-1-git-send-email-asmadeus@codewreck.org> From: Tomas Bortoli Openpgp: preference=signencrypt Autocrypt: addr=tomasbortoli@gmail.com; prefer-encrypt=mutual; keydata= mQINBFpCTZMBEADNZ1+Ibh0Z4pgGRcd1aOUMbe/YfHktmajjcoTnKmZZunjoUVAl8waeLITd BC2c8i1wHzHcnthrmb1izs5XlG6PZnl8n5tjysSNbwggzS1NcEK1qgn5VjNlHQ5aRMUwCC51 kicBiNmlQk2UuzzWwdheRGnaf+O1MNhC0GBeEDKQAL5obOU92pzflv6wWNACr+lHxdnpyies mOnRMjH16NjuTkrGbEmJe+MKp0qbjvR3R/dmFC1wczniRMQmV5w3MZ/N9wRappE+Atc1fOM+ wP7AWNuPvrKg4bN5uqKZLDFH7OFpxvjgVdWM40n0cQfqElWY9as+228Sltdd1XyHtUWRF2VW O1l5L0kX0+7+B5k/fpLhXqD3Z7DK7wRXpXmY59pofk7aFdcN97ZK+r6R7mqrwX4W9IpsPhkT kUyg3/Dx/khBZlJKFoUP325/hoH684bSiPEBroel9alB7gTq2ueoFwy6R3q5CMUw3D+CZWHA 3xllu46TRQ/Vt2g0cIHQNPoye2OWYFJ6kSEvaLpymjNDJ9ph2EuHegonDfOaYSq34ic2BcdB JkCgXRLP5K7KtRNJqqR+DM8xByeGmQv9yp6S97el+SiM9R53RhHawJZGz0EPl+2Q6+5mgh3u wXOlkmGrrSrlB8lc567l34ECl6NFtUPIL7H5vppIXAFl7JZUdQARAQABtB50b21hcyA8dG9t YXNib3J0b2xpQGdtYWlsLmNvbT6JAlQEEwEIAD4WIQSKOZIcNF9TdAG6W8ARUi5Y8x1zLgUC WkJNkwIbIwUJCWYBgAULCQgHAgYVCAkKCwIEFgIDAQIeAQIXgAAKCRARUi5Y8x1zLvCXD/9h iaZWJ6bC6jHHPGDMknFdbpNnB5w1hBivu9KwAm4LyEI+taWhmUg5WUNO1CmDa2WGSUSTk9lo uq7gH8Y7zwGrYOEDVuldjRjPFR/1yW2JdAmbwzcYkVU0ZUhyo2XzgFjsnv3vJGHk/afEopce U6mOc2BsGDpo2izVTE/HVaiLE9jyKQF6Riy04QBRAvxbDvx1rl26GIxVI6coBFf4SZhZOnc0 dzsip0/xaSRRIMG0d75weezIG49qK3IHyw2Fw5pEFY8tP0JJVxtrq2MZw+n4WmW9BVD/oCd/ b0JZ4volQbOFmdLzcAi2w7DMcKVkW11I1fiRZ/vLMvA4b79r6mn3WJ8aMIaodG6CQzmDNcsF br+XVp8rc58m9q69BTzDH0xTStxXiwozyISAe2VGbGUbK9ngU/H1RX0Y01uQ9Dz0KfyjA0/Z QOBa4N1n1qoKFzoxTpu0Vyumkc5EnTk8NdWszt7UAtNSaIZcBuWHR7Kp0DqRHwom0kgTiNXJ 8uNgvvFTkPd2Pdz1BqbpN1Fj856xPuKIiqs5qXI2yh3GhntFDbTOwOU3rr3x5NEv3wFVojdi HcLM+KVf29YkRHzuEQT5YT9h6qTk2aFRqq3HSXrP56hQ3whR7bQtziJspkuj+ekeTxcZ5lr4 9FJI03hQJ4HbHn6x/Xw0+WjIOo4jBeUEI7kCDQRaQk2TARAA4JCPcQcISPAKKC1n9VQxgdH3 oMqxhJ+gh/0Yb394ZYWLf7qOVQf/MgALPQIIFpcwYrw7gK4hsN7kj1vwPFy9JIqZtkgbmJHm aCj1LkZuf8tp5uvqzMZGcgm28IO6qDhPggeUE3hfA/y5++Vt0Jsmrz5zVPY0bOrLh1bItLnF U3uoaHWkAi/rhM6WwlsxemefzKulXoR9PIGVZ/QGjBGsTkNbTpiz2KsN+Ff/ZgjBJzGQNgha kc6a+eXyGC0YE8fRoTQekTi/GqGY7gfRKkgZDPi0Ul0sPZQJo07Dpw0nh5l6sOO+1yXygcoA V7I4bUeANZ9QJzbzZALgtxbT6jTKC0HUbF9iFb0yEkffkQuhhIqud7RkITe25hZePN8Y6Px0 yF4lEVW/Ti91jMSb4mpZiAaIFcdDV0CAtIYHAcK1ZRVz//+72o4gMZlRxowxduMyRs3L5rE0 ZkFQ6aPan+NBtEk1v3RPqnsQwJsonmiEgfbvybyBpP5MzRZnoAxfQ9vyyXoI5ofbl/+l9wv8 mosKNWIjiQsX3KiyaqygtD/yed5diie5nA7eT6IjL92WfgSelhBCL4jV0fL4w8hah2Azu0Jg 1ZtjjgoDObcAKQ5dLJA0IDsgH/X/G+ZMvkPpPIVaS5QWkiv66hixdKte/4iUrN+4waxJLCit 1KGC2xPJ2UUAEQEAAYkCPAQYAQgAJhYhBIo5khw0X1N0AbpbwBFSLljzHXMuBQJaQk2TAhsM BQkJZgGAAAoJEBFSLljzHXMuOb0P/1EnY4Y6LfQ6bmhJQ6epA3fB70hRWCQsuPYLAgPKRoXy kmWH4ljqQDbA55TtIpnod/woR0IDnZcD7E9cyGzM2rHvSLXTkHhgIWacZHZopAUzq4j0lhiJ Wu57freQPU4rzMVGZXBktUsDMsJwp/3Tl2Kjqylh90qIOlB9laUusLIbl4w5J3EscIJzWvdL y1lJLtBmus/t75wN/aIB8l9YBKGuy0L4SAmjhN52pCgP/S+ANEKvdghQco51a4jD2Pv2uYH7 nUU/Y70AmqOHjPR+qZ0hAUw6B+UtWQ+Fl587Qqi2XPUzdA8G2EjGFFPRlnhf2H/gOyAfeVYL NDwDgm9Yzp7Rx0O1QOnQsXTHqk7K38AdSdM2li/I/zegeblInnLi08Gq6mT6RkD6wV9HE5U3 EIU0rDPyJo54MW39wGjfC2+PM5I0xebbxtnuTewRchVVfm7UWgLAy11pV3xM4wMSJOuqVMOz jYpWKYxDTpvsZ0ginUUY993Gb8k/CxjABEMUGVHhQPZ0OzjHIKS6cTzN6ue8bB+CGOLCaQp1 C0NRT5Tn9zpLxtf5nBExFd/zVENY5vAV2ZbKQdemO54O7j6B9DSgVRrm83GCZxbL4d+qTYBF 3tSCWw/6SG1F3q9gR9QrSC2YRjCmhijUVEh6FhZwB58TNZ1sEEttrps8TDa5tUd9 Message-ID: <39a3c5f8-6cb6-c1cf-d10f-674e3244daee@gmail.com> Date: Mon, 17 Dec 2018 08:37:45 +0100 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.3.0 MIME-Version: 1.0 In-Reply-To: <1544532108-21689-1-git-send-email-asmadeus@codewreck.org> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hey Dominique, sorry for the delay, I've been quite busy these days. The patches looks good to me and should indeed speed up the code a bit. I quickly tested them against Syzkaller tuned for the 9p subsystem and everything seems fine. And by the way, which refcount races? Cheers, Tomas On 12/11/18 1:41 PM, Dominique Martinet wrote: > From: Dominique Martinet > > Add p9_client_async_rpc that will let us send an rpc without waiting > for the reply, as well as an async handler hook. > > The work done in the hook could mostly be done in the client callback, > but I prefered not to for a couple of reasons: > - the callback can be called in an IRQ for some transports, and the > handler needs to call p9_tag_remove which takes the client lock that has > recently been reworked to not be irq-compatible (as it was never taken > in IRQs until now) > - the handled replies can be handled anytime, there is nothing the > userspace would care about and want to be notified of quickly > - the async request list and this function would be needed anyway for > when we disconnect the client, in order to not leak async requests that > haven't been replied to > > Signed-off-by: Dominique Martinet > Cc: Eric Van Hensbergen > Cc: Latchesar Ionkov > Cc: Tomas Bortoli > Cc: Dmitry Vyukov > --- > > I've been sitting on these patches for almost a month now because I > wanted to fix the cancel race, but I think it's what the most recent > syzbot email is about so if it could find it without this it probably > won't hurt to at least get some reviews for these three patches first. > > I won't submit these for next cycle, so will only put them into -next > after 4.20 is released; hopefully I'll have time to look at the two > pending refcount races around that time. > Until then, comments please! > > > include/net/9p/client.h | 9 +++++- > net/9p/client.c | 64 +++++++++++++++++++++++++++++++++++++++++ > 2 files changed, 72 insertions(+), 1 deletion(-) > > diff --git a/include/net/9p/client.h b/include/net/9p/client.h > index 947a570307a6..a4ded7666c73 100644 > --- a/include/net/9p/client.h > +++ b/include/net/9p/client.h > @@ -89,7 +89,8 @@ enum p9_req_status_t { > * @tc: the request fcall structure > * @rc: the response fcall structure > * @aux: transport specific data (provided for trans_fd migration) > - * @req_list: link for higher level objects to chain requests > + * @req_list: link used by trans_fd > + * @async_list: link used to check on async requests > */ > struct p9_req_t { > int status; > @@ -100,6 +101,7 @@ struct p9_req_t { > struct p9_fcall rc; > void *aux; > struct list_head req_list; > + struct list_head async_list; > }; > > /** > @@ -110,6 +112,9 @@ struct p9_req_t { > * @trans_mod: module API instantiated with this client > * @status: connection state > * @trans: tranport instance state and API > + * @fcall_cache: kmem cache for client request data (msize-specific) > + * @async_req_lock: protects @async_req_list > + * @async_req_list: list of requests waiting a reply > * @fids: All active FID handles > * @reqs: All active requests. > * @name: node name used as client id > @@ -125,6 +130,8 @@ struct p9_client { > enum p9_trans_status status; > void *trans; > struct kmem_cache *fcall_cache; > + spinlock_t async_req_lock; > + struct list_head async_req_list; > > union { > struct { > diff --git a/net/9p/client.c b/net/9p/client.c > index 357214a51f13..0a67c3ccd4fd 100644 > --- a/net/9p/client.c > +++ b/net/9p/client.c > @@ -729,6 +729,62 @@ static struct p9_req_t *p9_client_prepare_req(struct p9_client *c, > return ERR_PTR(err); > } > > +static struct p9_req_t * > +p9_client_async_rpc(struct p9_client *c, int8_t type, const char *fmt, ...) > +{ > + va_list ap; > + int err; > + struct p9_req_t *req; > + > + va_start(ap, fmt); > + req = p9_client_prepare_req(c, type, c->msize, fmt, ap); > + va_end(ap); > + if (IS_ERR(req)) > + return req; > + > + err = c->trans_mod->request(c, req); > + if (err < 0) { > + /* bail out without flushing... */ > + p9_req_put(req); > + p9_tag_remove(c, req); > + if (err != -ERESTARTSYS && err != -EFAULT) > + c->status = Disconnected; > + return ERR_PTR(safe_errno(err)); > + } > + > + return req; > +} > + > +static void p9_client_handle_async(struct p9_client *c, bool free_all) > +{ > + struct p9_req_t *req, *nreq; > + > + /* it's ok to miss some async replies here, do a quick check without > + * lock first unless called with free_all > + */ > + if (!free_all && list_empty(&c->async_req_list)) > + return; > + > + spin_lock_irq(&c->async_req_lock); > + list_for_each_entry_safe(req, nreq, &c->async_req_list, async_list) { > + if (free_all && req->status < REQ_STATUS_RCVD) { > + p9_debug(P9_DEBUG_ERROR, > + "final async handler found req tag %d type %d status %d\n", > + req->tc.tag, req->tc.id, req->status); > + if (c->trans_mod->cancelled) > + c->trans_mod->cancelled(c, req); > + /* won't receive reply now */ > + p9_req_put(req); > + } > + if (free_all || req->status >= REQ_STATUS_RCVD) { > + /* Put old refs whatever reqs actually returned */ > + list_del(&req->async_list); > + p9_tag_remove(c, req); > + } > + } > + spin_unlock_irq(&c->async_req_lock); > +} > + > /** > * p9_client_rpc - issue a request and wait for a response > * @c: client session > @@ -746,6 +802,8 @@ p9_client_rpc(struct p9_client *c, int8_t type, const char *fmt, ...) > unsigned long flags; > struct p9_req_t *req; > > + p9_client_handle_async(c, 0); > + > va_start(ap, fmt); > req = p9_client_prepare_req(c, type, c->msize, fmt, ap); > va_end(ap); > @@ -841,6 +899,8 @@ static struct p9_req_t *p9_client_zc_rpc(struct p9_client *c, int8_t type, > unsigned long flags; > struct p9_req_t *req; > > + p9_client_handle_async(c, 0); > + > va_start(ap, fmt); > /* > * We allocate a inline protocol data of only 4k bytes. > @@ -1030,6 +1090,8 @@ struct p9_client *p9_client_create(const char *dev_name, char *options) > memcpy(clnt->name, client_id, strlen(client_id) + 1); > > spin_lock_init(&clnt->lock); > + spin_lock_init(&clnt->async_req_lock); > + INIT_LIST_HEAD(&clnt->async_req_list); > idr_init(&clnt->fids); > idr_init(&clnt->reqs); > > @@ -1101,6 +1163,8 @@ void p9_client_destroy(struct p9_client *clnt) > > v9fs_put_trans(clnt->trans_mod); > > + p9_client_handle_async(clnt, 1); > + > idr_for_each_entry(&clnt->fids, fid, id) { > pr_info("Found fid %d not clunked\n", fid->fid); > p9_fid_destroy(fid); >