[{"id":3677290,"web_url":"http://patchwork.ozlabs.org/comment/3677290/","msgid":"<87h5pdzgmn.fsf@suse.de>","list_archive_url":null,"date":"2026-04-14T15:49:36","subject":"Re: [PATCH v3 1/4] io/channel: introduce qio_channel_pread{v,\n }_all{, _eof}()","submitter":{"id":85343,"url":"http://patchwork.ozlabs.org/api/people/85343/","name":"Fabiano Rosas","email":"farosas@suse.de"},"content":"Junjie Cao writes:\n\n> qio_channel_pread() and qio_channel_preadv() perform a single\n> positioned read and may return a short result. Callers that need all\n> bytes currently have to open-code a retry loop or simply treat a short\n> read as an error.\n>\n> Introduce four new helpers following the existing read_all / readv_all\n> pattern:\n>\n> qio_channel_preadv_all_eof() -- retry loop; returns 1 on success,\n> 0 on clean EOF, -1 on error.\n> qio_channel_preadv_all() -- wraps _eof; treats early EOF as\n> error; returns 0 / -1.\n> qio_channel_pread_all_eof() -- single-buffer convenience wrapper\n> around preadv_all_eof().\n> qio_channel_pread_all() -- single-buffer convenience wrapper\n> around preadv_all().\n>\n> These advance the file offset internally after each partial read.\n> All four are marked coroutine_mixed_fn, consistent with the existing\n> _all helpers.\n>\n> Suggested-by: Peter Xu \n> Signed-off-by: Junjie Cao \n> ---\n> include/io/channel.h | 92 ++++++++++++++++++++++++++++++++++++++++++++\n> io/channel.c | 91 +++++++++++++++++++++++++++++++++++++++++++\n> 2 files changed, 183 insertions(+)\n>\n> diff --git a/include/io/channel.h b/include/io/channel.h\n> index 1b02350437..47af409ede 100644\n> --- a/include/io/channel.h\n> +++ b/include/io/channel.h\n> @@ -634,6 +634,98 @@ ssize_t qio_channel_preadv(QIOChannel *ioc, const struct iovec *iov,\n> ssize_t qio_channel_pread(QIOChannel *ioc, void *buf, size_t buflen,\n> off_t offset, Error **errp);\n> \n> +/**\n> + * qio_channel_preadv_all_eof:\n> + * @ioc: the channel object\n> + * @iov: the array of memory regions to read data into\n> + * @niov: the length of the @iov array\n> + * @offset: the starting offset in the channel to read from\n> + * @errp: pointer to a NULL-initialized error object\n> + *\n> + * Reads @iov, possibly blocking or (if the channel is non-blocking)\n> + * yielding from the current coroutine multiple times until the entire\n> + * content is read. If end-of-file occurs immediately it is not an\n> + * error, but if it occurs after data has been read it will return\n> + * an error rather than a short-read. Otherwise behaves as\n> + * qio_channel_preadv().\n> + *\n> + * Returns: 1 if all bytes were read, 0 if end-of-file occurs\n> + * without data, or -1 on error\n> + */\n> +int coroutine_mixed_fn qio_channel_preadv_all_eof(QIOChannel *ioc,\n> + const struct iovec *iov,\n> + size_t niov,\n> + off_t offset,\n> + Error **errp);\n> +\n> +/**\n> + * qio_channel_preadv_all:\n> + * @ioc: the channel object\n> + * @iov: the array of memory regions to read data into\n> + * @niov: the length of the @iov array\n> + * @offset: the starting offset in the channel to read from\n> + * @errp: pointer to a NULL-initialized error object\n> + *\n> + * Reads @iov, possibly blocking or (if the channel is non-blocking)\n> + * yielding from the current coroutine multiple times until the entire\n> + * content is read. If end-of-file occurs before all requested data\n> + * has been read, an error will be reported. Otherwise behaves as\n> + * qio_channel_preadv().\n> + *\n> + * Returns: 0 if all bytes were read, or -1 on error\n> + */\n> +int coroutine_mixed_fn qio_channel_preadv_all(QIOChannel *ioc,\n> + const struct iovec *iov,\n> + size_t niov,\n> + off_t offset,\n> + Error **errp);\n> +\n> +/**\n> + * qio_channel_pread_all_eof:\n> + * @ioc: the channel object\n> + * @buf: the memory region to read data into\n> + * @buflen: the number of bytes to read into @buf\n> + * @offset: the starting offset in the channel to read from\n> + * @errp: pointer to a NULL-initialized error object\n> + *\n> + * Reads @buflen bytes, possibly blocking or (if the channel is\n> + * non-blocking) yielding from the current coroutine multiple times\n> + * until the entire content is read. If end-of-file occurs\n> + * immediately it is not an error, but if it occurs after data has\n> + * been read it will return an error rather than a short-read.\n> + * Otherwise behaves as qio_channel_pread().\n> + *\n> + * Returns: 1 if all bytes were read, 0 if end-of-file occurs\n> + * without data, or -1 on error\n> + */\n> +int coroutine_mixed_fn qio_channel_pread_all_eof(QIOChannel *ioc,\n> + void *buf,\n> + size_t buflen,\n> + off_t offset,\n> + Error **errp);\n> +\n> +/**\n> + * qio_channel_pread_all:\n> + * @ioc: the channel object\n> + * @buf: the memory region to read data into\n> + * @buflen: the number of bytes to read into @buf\n> + * @offset: the starting offset in the channel to read from\n> + * @errp: pointer to a NULL-initialized error object\n> + *\n> + * Reads @buflen bytes, possibly blocking or (if the channel is\n> + * non-blocking) yielding from the current coroutine multiple times\n> + * until the entire content is read. If end-of-file occurs before\n> + * all requested data has been read, an error will be reported.\n> + * Otherwise behaves as qio_channel_pread().\n> + *\n> + * Returns: 0 if all bytes were read, or -1 on error\n> + */\n> +int coroutine_mixed_fn qio_channel_pread_all(QIOChannel *ioc,\n> + void *buf,\n> + size_t buflen,\n> + off_t offset,\n> + Error **errp);\n> +\n> /**\n> * qio_channel_shutdown:\n> * @ioc: the channel object\n> diff --git a/io/channel.c b/io/channel.c\n> index cc02d997a4..52c1abfcbc 100644\n> --- a/io/channel.c\n> +++ b/io/channel.c\n> @@ -507,6 +507,97 @@ ssize_t qio_channel_pread(QIOChannel *ioc, void *buf, size_t buflen,\n> return qio_channel_preadv(ioc, &iov, 1, offset, errp);\n> }\n> \n> +int coroutine_mixed_fn qio_channel_preadv_all_eof(QIOChannel *ioc,\n> + const struct iovec *iov,\n> + size_t niov,\n> + off_t offset,\n> + Error **errp)\n> +{\n> + int ret = -1;\n> + struct iovec *local_iov = g_new(struct iovec, niov);\n> + struct iovec *local_iov_head = local_iov;\n> + unsigned int nlocal_iov = niov;\n> + bool partial = false;\n> +\n> + nlocal_iov = iov_copy(local_iov, nlocal_iov,\n> + iov, niov,\n> + 0, iov_size(iov, niov));\n> +\n> + while (nlocal_iov > 0) {\n> + ssize_t len;\n> + len = qio_channel_preadv(ioc, local_iov, nlocal_iov, offset, errp);\n> +\n> + if (len == QIO_CHANNEL_ERR_BLOCK) {\n> + qio_channel_wait_cond(ioc, G_IO_IN);\n> + continue;\n> + }\n> +\n> + if (len == 0) {\n> + if (!partial) {\n> + ret = 0;\n> + goto cleanup;\n> + }\n> + error_setg(errp,\n> + \"Unexpected end-of-file before all data were read\");\n> + goto cleanup;\n> + }\n> +\n> + if (len < 0) {\n> + goto cleanup;\n> + }\n> +\n> + partial = true;\n> + offset += len;\n> + iov_discard_front(&local_iov, &nlocal_iov, len);\n> + }\n> +\n> + ret = 1;\n> +\n> + cleanup:\n> + g_free(local_iov_head);\n> + return ret;\n> +}\n> +\n> +int coroutine_mixed_fn qio_channel_preadv_all(QIOChannel *ioc,\n> + const struct iovec *iov,\n> + size_t niov,\n> + off_t offset,\n> + Error **errp)\n> +{\n> + int ret = qio_channel_preadv_all_eof(ioc, iov, niov, offset, errp);\n> +\n> + if (ret == 0) {\n> + error_setg(errp,\n> + \"Unexpected end-of-file before all data were read\");\n> + return -1;\n> + }\n> + if (ret == 1) {\n> + return 0;\n> + }\n> +\n> + return ret;\n> +}\n> +\n> +int coroutine_mixed_fn qio_channel_pread_all_eof(QIOChannel *ioc,\n> + void *buf,\n> + size_t buflen,\n> + off_t offset,\n> + Error **errp)\n> +{\n> + struct iovec iov = { .iov_base = buf, .iov_len = buflen };\n> + return qio_channel_preadv_all_eof(ioc, &iov, 1, offset, errp);\n> +}\n> +\n> +int coroutine_mixed_fn qio_channel_pread_all(QIOChannel *ioc,\n> + void *buf,\n> + size_t buflen,\n> + off_t offset,\n> + Error **errp)\n> +{\n> + struct iovec iov = { .iov_base = buf, .iov_len = buflen };\n> + return qio_channel_preadv_all(ioc, &iov, 1, offset, errp);\n> +}\n> +\n> int qio_channel_shutdown(QIOChannel *ioc,\n> QIOChannelShutdown how,\n> Error **errp)\n\nReviewed-by: Fabiano Rosas ","headers":{"Return-Path":"","X-Original-To":"incoming@patchwork.ozlabs.org","Delivered-To":"patchwork-incoming@legolas.ozlabs.org","Authentication-Results":["legolas.ozlabs.org;\n\tdkim=pass (1024-bit key;\n unprotected) header.d=suse.de header.i=@suse.de header.a=rsa-sha256\n header.s=susede2_rsa header.b=rsgtrsHU;\n\tdkim=pass header.d=suse.de header.i=@suse.de header.a=ed25519-sha256\n header.s=susede2_ed25519 header.b=NX3AbKL9;\n\tdkim=pass (1024-bit key) header.d=suse.de header.i=@suse.de\n header.a=rsa-sha256 header.s=susede2_rsa header.b=hOrhlE5i;\n\tdkim=neutral header.d=suse.de header.i=@suse.de header.a=ed25519-sha256\n header.s=susede2_ed25519 header.b=+XeVD1zS;\n\tdkim-atps=neutral","legolas.ozlabs.org;\n spf=pass (sender SPF authorized) smtp.mailfrom=nongnu.org\n (client-ip=209.51.188.17; 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