From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([209.51.188.92]:34755) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1gvldO-0006GK-Sp for qemu-devel@nongnu.org; Mon, 18 Feb 2019 11:19:12 -0500 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1gvldL-0002NX-DT for qemu-devel@nongnu.org; Mon, 18 Feb 2019 11:19:09 -0500 From: Kevin Wolf Date: Mon, 18 Feb 2019 17:18:16 +0100 Message-Id: <20190218161822.3573-7-kwolf@redhat.com> In-Reply-To: <20190218161822.3573-1-kwolf@redhat.com> References: <20190218161822.3573-1-kwolf@redhat.com> MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Subject: [Qemu-devel] [PATCH 06/12] nbd: Use low-level QIOChannel API in nbd_read_eof() List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: qemu-block@nongnu.org Cc: kwolf@redhat.com, mreitz@redhat.com, eblake@redhat.com, stefanha@redhat.com, berrange@redhat.com, pbonzini@redhat.com, qemu-devel@nongnu.org Instead of using the convenience wrapper qio_channel_read_all_eof(), use the lower level QIOChannel API. This means duplicating some code, but we'll need this because this coroutine yield is special: We want it to be interruptible so that nbd_client_attach_aio_context() can correctly reenter the coroutine. This moves the bdrv_dec/inc_in_flight() pair into nbd_read_eof(), so that connection_co will always sit in this exact qio_channel_yield() call when bdrv_drain() returns. Signed-off-by: Kevin Wolf --- include/block/nbd.h | 4 ++-- block/nbd-client.c | 8 +------- nbd/client.c | 46 ++++++++++++++++++++++++++++++++++++--------- 3 files changed, 40 insertions(+), 18 deletions(-) diff --git a/include/block/nbd.h b/include/block/nbd.h index cad975e00c..c6ef1ef42e 100644 --- a/include/block/nbd.h +++ b/include/block/nbd.h @@ -300,8 +300,8 @@ int nbd_receive_export_list(QIOChannel *ioc, QCryptoT= LSCreds *tlscreds, int nbd_init(int fd, QIOChannelSocket *sioc, NBDExportInfo *info, Error **errp); int nbd_send_request(QIOChannel *ioc, NBDRequest *request); -int coroutine_fn nbd_receive_reply(QIOChannel *ioc, NBDReply *reply, - Error **errp); +int coroutine_fn nbd_receive_reply(BlockDriverState *bs, QIOChannel *ioc= , + NBDReply *reply, Error **errp); int nbd_client(int fd); int nbd_disconnect(int fd); int nbd_errno_to_system_errno(int err); diff --git a/block/nbd-client.c b/block/nbd-client.c index e776785325..688993652d 100644 --- a/block/nbd-client.c +++ b/block/nbd-client.c @@ -84,15 +84,9 @@ static coroutine_fn void nbd_connection_entry(void *op= aque) * * Therefore we keep an additional in_flight reference all the t= ime and * only drop it temporarily here. - * - * FIXME This is not safe because the QIOChannel could wake up t= he - * coroutine for a second time; it is not prepared for coroutine - * resumption from external code. */ - bdrv_dec_in_flight(s->bs); assert(s->reply.handle =3D=3D 0); - ret =3D nbd_receive_reply(s->ioc, &s->reply, &local_err); - bdrv_inc_in_flight(s->bs); + ret =3D nbd_receive_reply(s->bs, s->ioc, &s->reply, &local_err); =20 if (local_err) { trace_nbd_read_reply_entry_fail(ret, error_get_pretty(local_= err)); diff --git a/nbd/client.c b/nbd/client.c index 28d174c0f3..de7da48246 100644 --- a/nbd/client.c +++ b/nbd/client.c @@ -1394,30 +1394,58 @@ static int nbd_receive_structured_reply_chunk(QIO= Channel *ioc, * negative errno on failure (errp is set) */ static inline int coroutine_fn -nbd_read_eof(QIOChannel *ioc, void *buffer, size_t size, Error **errp) +nbd_read_eof(BlockDriverState *bs, QIOChannel *ioc, void *buffer, size_t= size, + Error **errp) { - int ret; + bool partial =3D false; =20 assert(size); - ret =3D qio_channel_read_all_eof(ioc, buffer, size, errp); - if (ret < 0) { - ret =3D -EIO; + while (size > 0) { + struct iovec iov =3D { .iov_base =3D buffer, .iov_len =3D size }= ; + ssize_t len; + + len =3D qio_channel_readv(ioc, &iov, 1, errp); + if (len =3D=3D QIO_CHANNEL_ERR_BLOCK) { + bdrv_dec_in_flight(bs); + qio_channel_yield(ioc, G_IO_IN); + bdrv_inc_in_flight(bs); + continue; + } else if (len < 0) { + return -EIO; + } else if (len =3D=3D 0) { + if (partial) { + error_setg(errp, + "Unexpected end-of-file before all bytes were= read"); + return -EIO; + } else { + return 0; + } + } + + partial =3D true; + size -=3D len; + buffer =3D (uint8_t*) buffer + len; } - return ret; + return 1; } =20 /* nbd_receive_reply + * + * Decreases bs->in_flight while waiting for a new reply. This yield is = where + * we wait indefinitely and the coroutine must be able to be safely reen= tered + * for nbd_client_attach_aio_context(). + * * Returns 1 on success * 0 on eof, when no data was read (errp is not set) * negative errno on failure (errp is set) */ -int coroutine_fn nbd_receive_reply(QIOChannel *ioc, NBDReply *reply, - Error **errp) +int coroutine_fn nbd_receive_reply(BlockDriverState *bs, QIOChannel *ioc= , + NBDReply *reply, Error **errp) { int ret; const char *type; =20 - ret =3D nbd_read_eof(ioc, &reply->magic, sizeof(reply->magic), errp)= ; + ret =3D nbd_read_eof(bs, ioc, &reply->magic, sizeof(reply->magic), e= rrp); if (ret <=3D 0) { return ret; } --=20 2.20.1