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Re: [Qemu-block] [PATCH 07/10] io: add qio_channel_read/write_all
From: |
Paolo Bonzini |
Subject: |
Re: [Qemu-block] [PATCH 07/10] io: add qio_channel_read/write_all |
Date: |
Wed, 23 Aug 2017 08:54:01 +0200 |
User-agent: |
Mozilla/5.0 (X11; Linux x86_64; rv:52.0) Gecko/20100101 Thunderbird/52.2.1 |
On 23/08/2017 07:08, Fam Zheng wrote:
> On Tue, 08/22 15:18, Paolo Bonzini wrote:
>> It is pretty common to read a fixed-size buffer from a socket. Add a
>> function that does this, either with multiple reads (on blocking sockets)
>> or by yielding if called from a coroutine.
>>
>> Cc: Daniel P. Berrange <address@hidden>
>> Signed-off-by: Paolo Bonzini <address@hidden>
>> ---
>> include/io/channel.h | 36 ++++++++++++++++++++++++++++++++++-
>> io/channel.c | 54
>> ++++++++++++++++++++++++++++++++++++++++++++++++++++
>> 2 files changed, 89 insertions(+), 1 deletion(-)
>>
>> diff --git a/include/io/channel.h b/include/io/channel.h
>> index db9bb022a1..9cfb4d081f 100644
>> --- a/include/io/channel.h
>> +++ b/include/io/channel.h
>> @@ -299,7 +299,7 @@ ssize_t qio_channel_writev(QIOChannel *ioc,
>> Error **errp);
>>
>> /**
>> - * qio_channel_readv:
>> + * qio_channel_read:
>> * @ioc: the channel object
>> * @buf: the memory region to read data into
>> * @buflen: the length of @buf
>> @@ -315,6 +315,23 @@ ssize_t qio_channel_read(QIOChannel *ioc,
>> Error **errp);
>>
>> /**
>> + * qio_channel_read_all:
>> + * @ioc: the channel object
>> + * @buf: the memory region to read data into
>> + * @buflen: the number of bytes to @buf
>> + * @errp: pointer to a NULL-initialized error object
>> + *
>> + * Reads @buflen bytes into @buf, possibly blocking or (if the
>> + * channel is non-blocking) yielding from the current coroutine
>> + * multiple times until the entire content is read. Otherwise
>> + * behaves as qio_channel_read().
>> + */
>> +ssize_t coroutine_fn qio_channel_read_all(QIOChannel *ioc,
>> + char *buf,
>> + size_t buflen,
>> + Error **errp);
>> +
>> +/**
>> * qio_channel_write:
>> * @ioc: the channel object
>> * @buf: the memory regions to send data from
>> @@ -331,6 +348,23 @@ ssize_t qio_channel_write(QIOChannel *ioc,
>> Error **errp);
>>
>> /**
>> + * qio_channel_write_all:
>> + * @ioc: the channel object
>> + * @buf: the memory region to write data into
>> + * @buflen: the number of bytes to @buf
>> + * @errp: pointer to a NULL-initialized error object
>> + *
>> + * Writes @buflen bytes from @buf, possibly blocking or (if the
>> + * channel is non-blocking) yielding from the current coroutine
>> + * multiple times until the entire content is written. Otherwise
>> + * behaves as qio_channel_write().
>> + */
>> +ssize_t coroutine_fn qio_channel_write_all(QIOChannel *ioc,
>> + const char *buf,
>> + size_t buflen,
>> + Error **errp);
>> +
>> +/**
>> * qio_channel_set_blocking:
>> * @ioc: the channel object
>> * @enabled: the blocking flag state
>> diff --git a/io/channel.c b/io/channel.c
>> index 1cfb8b33a2..7ab3f4eede 100644
>> --- a/io/channel.c
>> +++ b/io/channel.c
>> @@ -113,6 +113,60 @@ ssize_t qio_channel_read(QIOChannel *ioc,
>> }
>>
>>
>> +ssize_t qio_channel_read_all(QIOChannel *ioc,
>> + char *buf,
>> + size_t buflen,
>> + Error **errp)
>> +{
>> + ssize_t total = 0;
>> + while (buflen > 0) {
>> + ssize_t n_read = qio_channel_read(ioc, buf, buflen, errp);
>> +
>> + if (n_read == QIO_CHANNEL_ERR_BLOCK) {
>> + assert(ioc->ctx);
>> + qio_channel_yield(ioc, G_IO_IN);
>> + continue;
>> + }
>> + if (n_read < 0) {
>> + return n_read;
>> + }
>> +
>> + buf += n_read;
>> + total += n_read;
>> + buflen -= n_read;
>> + }
>> +
>> + return total;
>> +}
>> +
>> +
>> +ssize_t qio_channel_write_all(QIOChannel *ioc,
>> + const char *buf,
>> + size_t buflen,
>> + Error **errp)
>> +{
>> + ssize_t total = 0;
>> + while (buflen > 0) {
>> + ssize_t n_written = qio_channel_write(ioc, buf, buflen, errp);
>> +
>> + if (n_written == QIO_CHANNEL_ERR_BLOCK) {
>> + assert(ioc->ctx);
>> + qio_channel_yield(ioc, G_IO_OUT);
>> + continue;
>> + }
>> + if (n_written < 0) {
>> + return n_written;
>> + }
>> +
>> + buf += n_written;
>> + total += n_written;
>> + buflen -= n_written;
>> + }
>> +
>> + return total;
>> +}
>> +
>> +
>> ssize_t qio_channel_write(QIOChannel *ioc,
>> const char *buf,
>> size_t buflen,
>> --
>> 2.13.5
>
> Are there any caller depending on short read/write? Is it okay to change all
> (or
> most) qio_channel_{read,write}* functions to this "full read/write" behavior?
No, it looks like I'm the first. :) NBD also implements something
similar to this patch, but it uses qio_channel_{read,write}v.
Paolo
- Re: [Qemu-block] [Qemu-devel] [PATCH 06/10] scsi, file-posix: add support for persistent reservation management, (continued)