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Registered Address: Red Hat UK Ltd, Amberley Place, 107-111 Peascod Street, Windsor, Berkshire, SI4 1TE, United Kingdom. Registered in England and Wales under Company Registration No. 3798903 From: David Howells To: Ilya Dryomov , netdev@vger.kernel.org cc: dhowells@redhat.com, Xiubo Li , Jeff Layton , "David S. Miller" , Eric Dumazet , Jakub Kicinski , Paolo Abeni , Jens Axboe , Matthew Wilcox , ceph-devel@vger.kernel.org, linux-kernel@vger.kernel.org Subject: [PATCH net-next] libceph: Partially revert changes to support MSG_SPLICE_PAGES MIME-Version: 1.0 Content-ID: <3101880.1687801973.1@warthog.procyon.org.uk> Date: Mon, 26 Jun 2023 18:52:53 +0100 Message-ID: <3101881.1687801973@warthog.procyon.org.uk> X-Scanned-By: MIMEDefang 3.1 on 10.11.54.7 Precedence: bulk List-ID: X-Mailing-List: ceph-devel@vger.kernel.org Fix the mishandling of MSG_DONTWAIT and also reinstates the per-page checking of the source pages (which might have come from a DIO write by userspace) by partially reverting the changes to support MSG_SPLICE_PAGES and doing things a little differently. In messenger_v1: (1) The ceph_tcp_sendpage() is resurrected and the callers reverted to use that. (2) The callers now pass MSG_MORE unconditionally. Previously, they were passing in MSG_MORE|MSG_SENDPAGE_NOTLAST and then degrading that to just MSG_MORE on the last call to ->sendpage(). (3) Make ceph_tcp_sendpage() a wrapper around sendmsg() rather than sendpage(), setting MSG_SPLICE_PAGES if sendpage_ok() returns true on the page. In messenger_v2: (4) Bring back do_try_sendpage() and make the callers use that. (5) Make do_try_sendpage() use sendmsg() for both cases and set MSG_SPLICE_PAGES if sendpage_ok() is set. Note that libceph is using sendpage_ok() for this, but it should not really be considered exhaustive in this regard - this is, however, what libceph is doing upstream. Fixes: 40a8c17aa770 ("ceph: Use sendmsg(MSG_SPLICE_PAGES) rather than sendpage") Fixes: fa094ccae1e7 ("ceph: Use sendmsg(MSG_SPLICE_PAGES) rather than sendpage()") Reported-by: Ilya Dryomov Link: https://lore.kernel.org/r/CAOi1vP9vjLfk3W+AJFeexC93jqPaPUn2dD_4NrzxwoZTbYfOnw@mail.gmail.com/ Link: https://lore.kernel.org/r/CAOi1vP_Bn918j24S94MuGyn+Gxk212btw7yWeDrRcW1U8pc_BA@mail.gmail.com/ Signed-off-by: David Howells cc: Ilya Dryomov cc: Xiubo Li cc: Jeff Layton cc: "David S. Miller" cc: Eric Dumazet cc: Jakub Kicinski cc: Paolo Abeni cc: Jens Axboe cc: Matthew Wilcox cc: ceph-devel@vger.kernel.org cc: netdev@vger.kernel.org --- net/ceph/messenger_v1.c | 57 +++++++++++++++++++------------ net/ceph/messenger_v2.c | 87 ++++++++++++++++++++++++++++++++++++++---------- 2 files changed, 105 insertions(+), 39 deletions(-) diff --git a/net/ceph/messenger_v1.c b/net/ceph/messenger_v1.c index 814579f27f04..1ee58cbaf151 100644 --- a/net/ceph/messenger_v1.c +++ b/net/ceph/messenger_v1.c @@ -74,6 +74,38 @@ static int ceph_tcp_sendmsg(struct socket *sock, struct kvec *iov, return r; } +/* + * @more: either or both of MSG_MORE and MSG_SENDPAGE_NOTLAST + */ +static int ceph_tcp_sendpage(struct socket *sock, struct page *page, + int offset, size_t size, int more) +{ + struct msghdr msg = { + .msg_flags = MSG_DONTWAIT | MSG_NOSIGNAL | more, + }; + struct bio_vec bvec; + int ret; + + /* + * sendpage cannot properly handle pages with page_count == 0, + * we need to fall back to sendmsg if that's the case. + * + * Same goes for slab pages: skb_can_coalesce() allows + * coalescing neighboring slab objects into a single frag which + * triggers one of hardened usercopy checks. + */ + if (sendpage_ok(page)) + msg.msg_flags |= MSG_SPLICE_PAGES; + + bvec_set_page(&bvec, page, size, offset); + + ret = sock_sendmsg(sock, &msg); + if (ret == -EAGAIN) + ret = 0; + + return ret; +} + static void con_out_kvec_reset(struct ceph_connection *con) { BUG_ON(con->v1.out_skip); @@ -450,10 +482,6 @@ static int write_partial_message_data(struct ceph_connection *con) */ crc = do_datacrc ? le32_to_cpu(msg->footer.data_crc) : 0; while (cursor->total_resid) { - struct bio_vec bvec; - struct msghdr msghdr = { - .msg_flags = MSG_SPLICE_PAGES, - }; struct page *page; size_t page_offset; size_t length; @@ -465,13 +493,8 @@ static int write_partial_message_data(struct ceph_connection *con) } page = ceph_msg_data_next(cursor, &page_offset, &length); - if (length != cursor->total_resid) - msghdr.msg_flags |= MSG_MORE; - - bvec_set_page(&bvec, page, length, page_offset); - iov_iter_bvec(&msghdr.msg_iter, ITER_SOURCE, &bvec, 1, length); - - ret = sock_sendmsg(con->sock, &msghdr); + ret = ceph_tcp_sendpage(con->sock, page, page_offset, length, + MSG_MORE); if (ret <= 0) { if (do_datacrc) msg->footer.data_crc = cpu_to_le32(crc); @@ -501,22 +524,14 @@ static int write_partial_message_data(struct ceph_connection *con) */ static int write_partial_skip(struct ceph_connection *con) { - struct bio_vec bvec; - struct msghdr msghdr = { - .msg_flags = MSG_SPLICE_PAGES | MSG_MORE, - }; int ret; dout("%s %p %d left\n", __func__, con, con->v1.out_skip); while (con->v1.out_skip > 0) { size_t size = min(con->v1.out_skip, (int)PAGE_SIZE); - if (size == con->v1.out_skip) - msghdr.msg_flags &= ~MSG_MORE; - bvec_set_page(&bvec, ZERO_PAGE(0), size, 0); - iov_iter_bvec(&msghdr.msg_iter, ITER_SOURCE, &bvec, 1, size); - - ret = sock_sendmsg(con->sock, &msghdr); + ret = ceph_tcp_sendpage(con->sock, ceph_zero_page, 0, size, + MSG_MORE); if (ret <= 0) goto out; con->v1.out_skip -= ret; diff --git a/net/ceph/messenger_v2.c b/net/ceph/messenger_v2.c index 87ac97073e75..139b61598f4f 100644 --- a/net/ceph/messenger_v2.c +++ b/net/ceph/messenger_v2.c @@ -117,38 +117,89 @@ static int ceph_tcp_recv(struct ceph_connection *con) return ret; } +static int do_sendmsg(struct socket *sock, struct iov_iter *it) +{ + struct msghdr msg = { .msg_flags = CEPH_MSG_FLAGS }; + int ret; + + msg.msg_iter = *it; + while (iov_iter_count(it)) { + ret = sock_sendmsg(sock, &msg); + if (ret <= 0) { + if (ret == -EAGAIN) + ret = 0; + return ret; + } + + iov_iter_advance(it, ret); + } + + WARN_ON(msg_data_left(&msg)); + return 1; +} + +static int do_try_sendpage(struct socket *sock, struct iov_iter *it) +{ + struct msghdr msg = {}; + struct bio_vec bv; + int ret; + + if (WARN_ON(!iov_iter_is_bvec(it))) + return -EINVAL; + + while (iov_iter_count(it)) { + msg.msg_flags = CEPH_MSG_FLAGS; + if (sendpage_ok(bv.bv_page)) + msg.msg_flags |= MSG_SPLICE_PAGES; + + /* iov_iter_iovec() for ITER_BVEC */ + bvec_set_page(&bv, it->bvec->bv_page, + min(iov_iter_count(it), + it->bvec->bv_len - it->iov_offset), + it->bvec->bv_offset + it->iov_offset); + + /* + * MSG_SPLICE_PAGES cannot properly handle pages with + * page_count == 0, we need to fall back to sendmsg if + * that's the case. + * + * Same goes for slab pages: skb_can_coalesce() allows + * coalescing neighboring slab objects into a single frag + * which triggers one of hardened usercopy checks. + */ + iov_iter_bvec(&msg.msg_iter, ITER_SOURCE, &bv, 1, bv.bv_len); + ret = sock_sendmsg(sock, &msg); + if (ret <= 0) { + if (ret == -EAGAIN) + ret = 0; + return ret; + } + + iov_iter_advance(it, ret); + } + + return 1; +} + /* * Write as much as possible. The socket is expected to be corked, * so we don't bother with MSG_MORE here. * * Return: - * >0 - done, nothing (else) to write + * 1 - done, nothing (else) to write * 0 - socket is full, need to wait * <0 - error */ static int ceph_tcp_send(struct ceph_connection *con) { - struct msghdr msg = { - .msg_iter = con->v2.out_iter, - .msg_flags = CEPH_MSG_FLAGS, - }; int ret; - if (WARN_ON(!iov_iter_is_bvec(&con->v2.out_iter))) - return -EINVAL; - - if (con->v2.out_iter_sendpage) - msg.msg_flags |= MSG_SPLICE_PAGES; - dout("%s con %p have %zu try_sendpage %d\n", __func__, con, iov_iter_count(&con->v2.out_iter), con->v2.out_iter_sendpage); - - ret = sock_sendmsg(con->sock, &msg); - if (ret > 0) - iov_iter_advance(&con->v2.out_iter, ret); - else if (ret == -EAGAIN) - ret = 0; - + if (con->v2.out_iter_sendpage) + ret = do_try_sendpage(con->sock, &con->v2.out_iter); + else + ret = do_sendmsg(con->sock, &con->v2.out_iter); dout("%s con %p ret %d left %zu\n", __func__, con, ret, iov_iter_count(&con->v2.out_iter)); return ret;