From b88651cb4d4fa416fdbb6afaf5b26ec8c035eaad Mon Sep 17 00:00:00 2001 From: Leonardo Bras Date: Fri, 13 May 2022 03:28:31 -0300 Subject: QIOChannel: Add flags on io_writev and introduce io_flush callback MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Add flags to io_writev and introduce io_flush as optional callback to QIOChannelClass, allowing the implementation of zero copy writes by subclasses. How to use them: - Write data using qio_channel_writev*(...,QIO_CHANNEL_WRITE_FLAG_ZERO_COPY), - Wait write completion with qio_channel_flush(). Notes: As some zero copy write implementations work asynchronously, it's recommended to keep the write buffer untouched until the return of qio_channel_flush(), to avoid the risk of sending an updated buffer instead of the buffer state during write. As io_flush callback is optional, if a subclass does not implement it, then: - io_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 zero copy and non-zero copy writev, and also an easier implementation on new flags. Signed-off-by: Leonardo Bras Reviewed-by: Daniel P. Berrangé Reviewed-by: Peter Xu Reviewed-by: Juan Quintela Message-Id: <20220513062836.965425-3-leobras@redhat.com> Signed-off-by: Dr. David Alan Gilbert --- include/io/channel.h | 38 +++++++++++++++++++++++++++++++++++++- 1 file changed, 37 insertions(+), 1 deletion(-) (limited to 'include/io') diff --git a/include/io/channel.h b/include/io/channel.h index 88988979f8..c680ee7480 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_ZERO_COPY 0x1 + typedef enum QIOChannelFeature QIOChannelFeature; enum QIOChannelFeature { QIO_CHANNEL_FEATURE_FD_PASS, QIO_CHANNEL_FEATURE_SHUTDOWN, QIO_CHANNEL_FEATURE_LISTEN, + QIO_CHANNEL_FEATURE_WRITE_ZERO_COPY, }; @@ -104,6 +107,7 @@ struct QIOChannelClass { size_t niov, int *fds, size_t nfds, + int flags, Error **errp); ssize_t (*io_readv)(QIOChannel *ioc, const struct iovec *iov, @@ -136,6 +140,8 @@ struct QIOChannelClass { IOHandler *io_read, IOHandler *io_write, void *opaque); + int (*io_flush)(QIOChannel *ioc, + Error **errp); }; /* General I/O handling functions */ @@ -228,6 +234,7 @@ ssize_t qio_channel_readv_full(QIOChannel *ioc, * @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 @@ -260,6 +267,7 @@ ssize_t qio_channel_writev_full(QIOChannel *ioc, size_t niov, int *fds, size_t nfds, + int flags, Error **errp); /** @@ -837,6 +845,7 @@ int qio_channel_readv_full_all(QIOChannel *ioc, * @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 * * @@ -846,6 +855,14 @@ int qio_channel_readv_full_all(QIOChannel *ioc, * to be written, yielding from the current coroutine * if required. * + * If QIO_CHANNEL_WRITE_FLAG_ZERO_COPY 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. + * In this case, if the buffer gets changed between queueing and + * sending, the updated buffer will be sent. If this is not a + * desired behavior, it's suggested to call qio_channel_flush() + * before reusing the buffer. + * * Returns: 0 if all bytes were written, or -1 on error */ @@ -853,6 +870,25 @@ int qio_channel_writev_full_all(QIOChannel *ioc, const struct iovec *iov, size_t niov, int *fds, size_t nfds, - Error **errp); + int flags, Error **errp); + +/** + * qio_channel_flush: + * @ioc: the channel object + * @errp: pointer to a NULL-initialized error object + * + * Will block until every packet queued with + * qio_channel_writev_full() + QIO_CHANNEL_WRITE_FLAG_ZERO_COPY + * is sent, or return in case of any error. + * + * If not implemented, acts as a no-op, and returns 0. + * + * Returns -1 if any error is found, + * 1 if every send failed to use zero copy. + * 0 otherwise. + */ + +int qio_channel_flush(QIOChannel *ioc, + Error **errp); #endif /* QIO_CHANNEL_H */ -- cgit v1.2.3