Adds io_async_writev and io_async_flush as optional callback to QIOChannelClass, allowing the implementation of asynchronous writes by subclasses.
How to use them: - Write data using qio_channel_writev_zerocopu(), - Wait write completion with qio_channel_flush_zerocopy(). Notes: As some zerocopy implementations work asynchronously, it's recommended to keep the write buffer untouched until the return of qio_channel_flush_zerocopy(), by the risk of sending an updated buffer instead of the one at the write. As the new callbacks are optional, if a subclass does not implement them, then: - io_async_writev will return -1, - io_async_flush will return 0 without changing anything. Also, some functions like qio_channel_writev_full_all() were adapted to receive a flag parameter. That allows shared code between zerocopy and non-zerocopy writev. Signed-off-by: Leonardo Bras <leob...@redhat.com> --- include/io/channel.h | 103 +++++++++++++++++++++++++++++++++++-------- io/channel.c | 74 +++++++++++++++++++++++-------- 2 files changed, 141 insertions(+), 36 deletions(-) diff --git a/include/io/channel.h b/include/io/channel.h index 88988979f8..e7d4e1521f 100644 --- a/include/io/channel.h +++ b/include/io/channel.h @@ -32,12 +32,15 @@ OBJECT_DECLARE_TYPE(QIOChannel, QIOChannelClass, #define QIO_CHANNEL_ERR_BLOCK -2 +#define QIO_CHANNEL_WRITE_FLAG_ZEROCOPY 0x1 + typedef enum QIOChannelFeature QIOChannelFeature; enum QIOChannelFeature { QIO_CHANNEL_FEATURE_FD_PASS, QIO_CHANNEL_FEATURE_SHUTDOWN, QIO_CHANNEL_FEATURE_LISTEN, + QIO_CHANNEL_FEATURE_WRITE_ZEROCOPY, }; @@ -136,6 +139,12 @@ struct QIOChannelClass { IOHandler *io_read, IOHandler *io_write, void *opaque); + ssize_t (*io_writev_zerocopy)(QIOChannel *ioc, + const struct iovec *iov, + size_t niov, + Error **errp); + int (*io_flush_zerocopy)(QIOChannel *ioc, + Error **errp); }; /* General I/O handling functions */ @@ -222,12 +231,13 @@ ssize_t qio_channel_readv_full(QIOChannel *ioc, /** - * qio_channel_writev_full: + * qio_channel_writev_full_flags: * @ioc: the channel object * @iov: the array of memory regions to write data from * @niov: the length of the @iov array * @fds: an array of file handles to send * @nfds: number of file handles in @fds + * @flags: write flags (QIO_CHANNEL_WRITE_FLAG_*) * @errp: pointer to a NULL-initialized error object * * Write data to the IO channel, reading it from the @@ -242,6 +252,10 @@ ssize_t qio_channel_readv_full(QIOChannel *ioc, * guaranteed. If the channel is non-blocking and no * data can be sent, it will return QIO_CHANNEL_ERR_BLOCK * + * If flag QIO_CHANNEL_WRITE_FLAG_ZEROCOPY is passed, + * function will return once each buffer was queued for + * sending. + * * If there are file descriptors to send, the @fds * array should be non-NULL and provide the handles. * All file descriptors will be sent if at least one @@ -255,12 +269,15 @@ ssize_t qio_channel_readv_full(QIOChannel *ioc, * or QIO_CHANNEL_ERR_BLOCK if no data is can be sent * and the channel is non-blocking */ -ssize_t qio_channel_writev_full(QIOChannel *ioc, - const struct iovec *iov, - size_t niov, - int *fds, - size_t nfds, - Error **errp); +ssize_t qio_channel_writev_full_flags(QIOChannel *ioc, + const struct iovec *iov, + size_t niov, + int *fds, + size_t nfds, + int flags, + Error **errp); +#define qio_channel_writev_full(ioc, iov, niov, fds, nfds, errp) \ + qio_channel_writev_full_flags(ioc, iov, niov, fds, nfds, 0, errp) /** * qio_channel_readv_all_eof: @@ -321,10 +338,11 @@ int qio_channel_readv_all(QIOChannel *ioc, /** - * qio_channel_writev_all: + * qio_channel_writev_all_flags: * @ioc: the channel object * @iov: the array of memory regions to write data from * @niov: the length of the @iov array + * @flags: write flags (QIO_CHANNEL_WRITE_FLAG_*) * @errp: pointer to a NULL-initialized error object * * Write data to the IO channel, reading it from the @@ -339,10 +357,13 @@ int qio_channel_readv_all(QIOChannel *ioc, * * Returns: 0 if all bytes were written, or -1 on error */ -int qio_channel_writev_all(QIOChannel *ioc, - const struct iovec *iov, - size_t niov, - Error **erp); +int qio_channel_writev_all_flags(QIOChannel *ioc, + const struct iovec *iov, + size_t niov, + int flags, + Error **errp); +#define qio_channel_writev_all(ioc, iov, niov, errp) \ + qio_channel_writev_all_flags(ioc, iov, niov, 0, errp) /** * qio_channel_readv: @@ -831,12 +852,13 @@ int qio_channel_readv_full_all(QIOChannel *ioc, Error **errp); /** - * qio_channel_writev_full_all: + * qio_channel_writev_full_all_flags: * @ioc: the channel object * @iov: the array of memory regions to write data from * @niov: the length of the @iov array * @fds: an array of file handles to send * @nfds: number of file handles in @fds + * @flags: write flags (QIO_CHANNEL_WRITE_FLAG_*) * @errp: pointer to a NULL-initialized error object * * @@ -846,13 +868,58 @@ int qio_channel_readv_full_all(QIOChannel *ioc, * to be written, yielding from the current coroutine * if required. * + * If QIO_CHANNEL_WRITE_FLAG_ZEROCOPY is passed in flags, + * instead of waiting for all requested data to be written, + * this function will wait until it's all queued for writing. + * * Returns: 0 if all bytes were written, or -1 on error */ -int qio_channel_writev_full_all(QIOChannel *ioc, - const struct iovec *iov, - size_t niov, - int *fds, size_t nfds, - Error **errp); +int qio_channel_writev_full_all_flags(QIOChannel *ioc, + const struct iovec *iov, + size_t niov, + int *fds, size_t nfds, + int flags, Error **errp); +#define qio_channel_writev_full_all(ioc, iov, niov, fds, nfds, errp) \ + qio_channel_writev_full_all_flags(ioc, iov, niov, fds, nfds, 0, errp) + +/** + * qio_channel_writev_zerocopy: + * @ioc: the channel object + * @iov: the array of memory regions to write data from + * @niov: the length of the @iov array + * @errp: pointer to a NULL-initialized error object + * + * Behaves like qio_channel_writev_full_all_flags, but will write + * data asynchronously while avoiding unnecessary data copy. + * This function may return before any data is actually written, + * but should queue every buffer for writting. + * + * If at some point it's necessary wait for all data to be + * written, use qio_channel_flush_zerocopy(). + * + * If zerocopy is not available, returns -1 and set errp. + */ + +ssize_t qio_channel_writev_zerocopy(QIOChannel *ioc, + const struct iovec *iov, + size_t niov, + Error **errp); + +/** + * qio_channel_flush_zerocopy: + * @ioc: the channel object + * @errp: pointer to a NULL-initialized error object + * + * Will lock until every packet queued with + * qio_channel_writev_zerocopy() is sent, or return + * in case of any error. + * + * Returns -1 if any error is found, 0 otherwise. + * If not implemented, returns 0 without changing anything. + */ + +int qio_channel_flush_zerocopy(QIOChannel *ioc, + Error **errp); #endif /* QIO_CHANNEL_H */ diff --git a/io/channel.c b/io/channel.c index e8b019dc36..811c93ae23 100644 --- a/io/channel.c +++ b/io/channel.c @@ -67,15 +67,27 @@ ssize_t qio_channel_readv_full(QIOChannel *ioc, } -ssize_t qio_channel_writev_full(QIOChannel *ioc, - const struct iovec *iov, - size_t niov, - int *fds, - size_t nfds, - Error **errp) +ssize_t qio_channel_writev_full_flags(QIOChannel *ioc, + const struct iovec *iov, + size_t niov, + int *fds, + size_t nfds, + int flags, + Error **errp) { QIOChannelClass *klass = QIO_CHANNEL_GET_CLASS(ioc); + if (flags & QIO_CHANNEL_WRITE_FLAG_ZEROCOPY) { + if (!klass->io_writev_zerocopy || + !qio_channel_has_feature(ioc, QIO_CHANNEL_FEATURE_WRITE_ZEROCOPY)) { + error_setg_errno(errp, EINVAL, + "Channel does not support zerocopy writev"); + return -1; + } + + return klass->io_writev_zerocopy(ioc, iov, niov, errp); + } + if ((fds || nfds) && !qio_channel_has_feature(ioc, QIO_CHANNEL_FEATURE_FD_PASS)) { error_setg_errno(errp, EINVAL, @@ -212,19 +224,20 @@ int qio_channel_readv_full_all(QIOChannel *ioc, return ret; } -int qio_channel_writev_all(QIOChannel *ioc, - const struct iovec *iov, - size_t niov, - Error **errp) +int qio_channel_writev_all_flags(QIOChannel *ioc, + const struct iovec *iov, + size_t niov, + int flags, + Error **errp) { - return qio_channel_writev_full_all(ioc, iov, niov, NULL, 0, errp); + return qio_channel_writev_full_all_flags(ioc, iov, niov, NULL, 0, flags, errp); } -int qio_channel_writev_full_all(QIOChannel *ioc, - const struct iovec *iov, - size_t niov, - int *fds, size_t nfds, - Error **errp) +int qio_channel_writev_full_all_flags(QIOChannel *ioc, + const struct iovec *iov, + size_t niov, + int *fds, size_t nfds, + int flags, Error **errp) { int ret = -1; struct iovec *local_iov = g_new(struct iovec, niov); @@ -237,8 +250,8 @@ int qio_channel_writev_full_all(QIOChannel *ioc, while (nlocal_iov > 0) { ssize_t len; - len = qio_channel_writev_full(ioc, local_iov, nlocal_iov, fds, nfds, - errp); + len = qio_channel_writev_full_flags(ioc, local_iov, nlocal_iov, fds, nfds, + flags, errp); if (len == QIO_CHANNEL_ERR_BLOCK) { if (qemu_in_coroutine()) { qio_channel_yield(ioc, G_IO_OUT); @@ -474,6 +487,31 @@ off_t qio_channel_io_seek(QIOChannel *ioc, } +ssize_t qio_channel_writev_zerocopy(QIOChannel *ioc, + const struct iovec *iov, + size_t niov, + Error **errp) +{ + return qio_channel_writev_full_flags(ioc, iov, niov, NULL, 0, + QIO_CHANNEL_WRITE_FLAG_ZEROCOPY, + errp); +} + + +int qio_channel_flush_zerocopy(QIOChannel *ioc, + Error **errp) +{ + QIOChannelClass *klass = QIO_CHANNEL_GET_CLASS(ioc); + + if (!klass->io_flush_zerocopy || + !qio_channel_has_feature(ioc, QIO_CHANNEL_FEATURE_WRITE_ZEROCOPY)) { + return 0; + } + + return klass->io_flush_zerocopy(ioc, errp); +} + + static void qio_channel_restart_read(void *opaque) { QIOChannel *ioc = opaque; -- 2.33.0