From: Junjie Cao Date: Mon, 13 Apr 2026 21:45:46 +0000 (+0800) Subject: io/channel: introduce qio_channel_pread{v, }_all{, _eof}() X-Git-Tag: v11.1.0-rc0~157^2~7 X-Git-Url: http://git.ipfire.org/gitweb.cgi?a=commitdiff_plain;h=2dd53f732b39c683064cc22ef040a1ece94e5e7f;p=thirdparty%2Fqemu.git io/channel: introduce qio_channel_pread{v, }_all{, _eof}() qio_channel_pread() and qio_channel_preadv() perform a single positioned read and may return a short result. Callers that need all bytes currently have to open-code a retry loop or simply treat a short read as an error. Introduce four new helpers following the existing read_all / readv_all pattern: qio_channel_preadv_all_eof() -- retry loop; returns 1 on success, 0 on clean EOF, -1 on error. qio_channel_preadv_all() -- wraps _eof; treats early EOF as error; returns 0 / -1. qio_channel_pread_all_eof() -- single-buffer convenience wrapper around preadv_all_eof(). qio_channel_pread_all() -- single-buffer convenience wrapper around preadv_all(). These advance the file offset internally after each partial read. All four are marked coroutine_mixed_fn, consistent with the existing _all helpers. Suggested-by: Peter Xu Signed-off-by: Junjie Cao Reviewed-by: Fabiano Rosas Reviewed-by: Daniel P. Berrangé Acked-by: Daniel P. Berrangé Link: https://lore.kernel.org/qemu-devel/20260413214549.926435-2-junjie.cao@intel.com Signed-off-by: Fabiano Rosas --- diff --git a/include/io/channel.h b/include/io/channel.h index 1b02350437d..47af409ede8 100644 --- a/include/io/channel.h +++ b/include/io/channel.h @@ -634,6 +634,98 @@ ssize_t qio_channel_preadv(QIOChannel *ioc, const struct iovec *iov, ssize_t qio_channel_pread(QIOChannel *ioc, void *buf, size_t buflen, off_t offset, Error **errp); +/** + * qio_channel_preadv_all_eof: + * @ioc: the channel object + * @iov: the array of memory regions to read data into + * @niov: the length of the @iov array + * @offset: the starting offset in the channel to read from + * @errp: pointer to a NULL-initialized error object + * + * Reads @iov, possibly blocking or (if the channel is non-blocking) + * yielding from the current coroutine multiple times until the entire + * content is read. If end-of-file occurs immediately it is not an + * error, but if it occurs after data has been read it will return + * an error rather than a short-read. Otherwise behaves as + * qio_channel_preadv(). + * + * Returns: 1 if all bytes were read, 0 if end-of-file occurs + * without data, or -1 on error + */ +int coroutine_mixed_fn qio_channel_preadv_all_eof(QIOChannel *ioc, + const struct iovec *iov, + size_t niov, + off_t offset, + Error **errp); + +/** + * qio_channel_preadv_all: + * @ioc: the channel object + * @iov: the array of memory regions to read data into + * @niov: the length of the @iov array + * @offset: the starting offset in the channel to read from + * @errp: pointer to a NULL-initialized error object + * + * Reads @iov, possibly blocking or (if the channel is non-blocking) + * yielding from the current coroutine multiple times until the entire + * content is read. If end-of-file occurs before all requested data + * has been read, an error will be reported. Otherwise behaves as + * qio_channel_preadv(). + * + * Returns: 0 if all bytes were read, or -1 on error + */ +int coroutine_mixed_fn qio_channel_preadv_all(QIOChannel *ioc, + const struct iovec *iov, + size_t niov, + off_t offset, + Error **errp); + +/** + * qio_channel_pread_all_eof: + * @ioc: the channel object + * @buf: the memory region to read data into + * @buflen: the number of bytes to read into @buf + * @offset: the starting offset in the channel to read from + * @errp: pointer to a NULL-initialized error object + * + * Reads @buflen bytes, possibly blocking or (if the channel is + * non-blocking) yielding from the current coroutine multiple times + * until the entire content is read. If end-of-file occurs + * immediately it is not an error, but if it occurs after data has + * been read it will return an error rather than a short-read. + * Otherwise behaves as qio_channel_pread(). + * + * Returns: 1 if all bytes were read, 0 if end-of-file occurs + * without data, or -1 on error + */ +int coroutine_mixed_fn qio_channel_pread_all_eof(QIOChannel *ioc, + void *buf, + size_t buflen, + off_t offset, + Error **errp); + +/** + * qio_channel_pread_all: + * @ioc: the channel object + * @buf: the memory region to read data into + * @buflen: the number of bytes to read into @buf + * @offset: the starting offset in the channel to read from + * @errp: pointer to a NULL-initialized error object + * + * Reads @buflen bytes, possibly blocking or (if the channel is + * non-blocking) yielding from the current coroutine multiple times + * until the entire content is read. If end-of-file occurs before + * all requested data has been read, an error will be reported. + * Otherwise behaves as qio_channel_pread(). + * + * Returns: 0 if all bytes were read, or -1 on error + */ +int coroutine_mixed_fn qio_channel_pread_all(QIOChannel *ioc, + void *buf, + size_t buflen, + off_t offset, + Error **errp); + /** * qio_channel_shutdown: * @ioc: the channel object diff --git a/io/channel.c b/io/channel.c index cc02d997a4d..52c1abfcbca 100644 --- a/io/channel.c +++ b/io/channel.c @@ -507,6 +507,97 @@ ssize_t qio_channel_pread(QIOChannel *ioc, void *buf, size_t buflen, return qio_channel_preadv(ioc, &iov, 1, offset, errp); } +int coroutine_mixed_fn qio_channel_preadv_all_eof(QIOChannel *ioc, + const struct iovec *iov, + size_t niov, + off_t offset, + Error **errp) +{ + int ret = -1; + struct iovec *local_iov = g_new(struct iovec, niov); + struct iovec *local_iov_head = local_iov; + unsigned int nlocal_iov = niov; + bool partial = false; + + nlocal_iov = iov_copy(local_iov, nlocal_iov, + iov, niov, + 0, iov_size(iov, niov)); + + while (nlocal_iov > 0) { + ssize_t len; + len = qio_channel_preadv(ioc, local_iov, nlocal_iov, offset, errp); + + if (len == QIO_CHANNEL_ERR_BLOCK) { + qio_channel_wait_cond(ioc, G_IO_IN); + continue; + } + + if (len == 0) { + if (!partial) { + ret = 0; + goto cleanup; + } + error_setg(errp, + "Unexpected end-of-file before all data were read"); + goto cleanup; + } + + if (len < 0) { + goto cleanup; + } + + partial = true; + offset += len; + iov_discard_front(&local_iov, &nlocal_iov, len); + } + + ret = 1; + + cleanup: + g_free(local_iov_head); + return ret; +} + +int coroutine_mixed_fn qio_channel_preadv_all(QIOChannel *ioc, + const struct iovec *iov, + size_t niov, + off_t offset, + Error **errp) +{ + int ret = qio_channel_preadv_all_eof(ioc, iov, niov, offset, errp); + + if (ret == 0) { + error_setg(errp, + "Unexpected end-of-file before all data were read"); + return -1; + } + if (ret == 1) { + return 0; + } + + return ret; +} + +int coroutine_mixed_fn qio_channel_pread_all_eof(QIOChannel *ioc, + void *buf, + size_t buflen, + off_t offset, + Error **errp) +{ + struct iovec iov = { .iov_base = buf, .iov_len = buflen }; + return qio_channel_preadv_all_eof(ioc, &iov, 1, offset, errp); +} + +int coroutine_mixed_fn qio_channel_pread_all(QIOChannel *ioc, + void *buf, + size_t buflen, + off_t offset, + Error **errp) +{ + struct iovec iov = { .iov_base = buf, .iov_len = buflen }; + return qio_channel_preadv_all(ioc, &iov, 1, offset, errp); +} + int qio_channel_shutdown(QIOChannel *ioc, QIOChannelShutdown how, Error **errp)