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Re: [PATCH v3 04/14] io: Add generic pwritev/preadv interface
From: |
Daniel P . Berrangé |
Subject: |
Re: [PATCH v3 04/14] io: Add generic pwritev/preadv interface |
Date: |
Fri, 10 Feb 2023 16:26:22 +0000 |
User-agent: |
Mutt/2.2.9 (2022-11-12) |
On Fri, Oct 28, 2022 at 01:39:04PM +0300, Nikolay Borisov wrote:
> Introduce basic pwriteve/preadv support in the generic channel layer.
> SPecific implementation will follow for the file channel as this is
> required in order to support migration streams with fixed location of
> each ram page.
>
> Signed-off-by: Nikolay Borisov <nborisov@suse.com>
> ---
> include/io/channel.h | 49 ++++++++++++++++++++++++++++++++++++++++++++
> io/channel.c | 26 +++++++++++++++++++++++
> 2 files changed, 75 insertions(+)
>
> diff --git a/include/io/channel.h b/include/io/channel.h
> index c680ee748021..6b10bce8bbdf 100644
> --- a/include/io/channel.h
> +++ b/include/io/channel.h
> @@ -124,6 +124,16 @@ struct QIOChannelClass {
> Error **errp);
>
> /* Optional callbacks */
> + ssize_t (*io_pwritev)(QIOChannel *ioc,
> + const struct iovec *iov,
> + size_t niov,
> + off_t offset,
> + Error **errp);
> + ssize_t (*io_preadv)(QIOChannel *ioc,
> + const struct iovec *iov,
> + size_t niov,
> + off_t offset,
> + Error **errp);
nit-pick the alignment of the 2nd line of parameters onwards,
needs to be indented by 3 more spaces.
> +/**
> + * qio_channel_io_pwritev
> + * @ioc: the channel object
> + * @iov: the array of memory regions to write data from
> + * @niov: the length of the @iov array
> + * @offset: offset in the channel where writes should begin
> + * @errp: pointer to a NULL-initialized error object
> + *
> + * Not all implementations will support this facility, so may report an
> error.
> + * To avoid errors, the caller may check for the feature flag
> + * QIO_CHANNEL_FEATURE_SEEKABLE prior to calling this method.
> + *
> + * Behaves as qio_channel_writev_full, apart from not supporting sending of
> file
Given this, we should have "_full" suffix on these methods
too for consistent naming policy.
> + * handles as well as beginning the write at the passed @offset
> + *
> + */
> +ssize_t qio_channel_io_pwritev(QIOChannel *ioc, const struct iovec *iov,
> + size_t niov, off_t offset, Error **errp);
> +
> +
> +/**
> + * qio_channel_io_preadv
> + * @ioc: the channel object
> + * @iov: the array of memory regions to read data into
> + * @niov: the length of the @iov array
> + * @offset: offset in the channel where writes should begin
> + * @errp: pointer to a NULL-initialized error object
> + *
> + * Not all implementations will support this facility, so may report an
> error.
> + * To avoid errors, the caller may check for the feature flag
> + * QIO_CHANNEL_FEATURE_SEEKABLE prior to calling this method.
> + *
> + * Behaves as qio_channel_readv_full, apart from not supporting receiving of
> file
> + * handles as well as beginning the read at the passed @offset
> + *
> + */
> +ssize_t qio_channel_io_preadv(QIOChannel *ioc, const struct iovec *iov,
> + size_t niov, off_t offset, Error **errp);
> /**
> * qio_channel_shutdown:
> * @ioc: the channel object
> diff --git a/io/channel.c b/io/channel.c
> index 0640941ac573..f5ac9499a7ad 100644
> --- a/io/channel.c
> +++ b/io/channel.c
> @@ -437,6 +437,32 @@ GSource *qio_channel_add_watch_source(QIOChannel *ioc,
> }
>
>
> +ssize_t qio_channel_io_pwritev(QIOChannel *ioc, const struct iovec *iov,
> + size_t niov, off_t offset, Error **errp)
> +{
> + QIOChannelClass *klass = QIO_CHANNEL_GET_CLASS(ioc);
> +
> + if (!klass->io_pwritev) {
> + error_setg(errp, "Channel does not support pwritev");
> + return -1;
> + }
This also possibly benefits from a validation check
if (!qio_channel_has_feature(ioc, QIO_CHANNEL_FEATURE_SEEKABLE)) {
error_setg_errno(errp, EINVAL,
"Requested channel is not seekable")
return -1;
}
because the QIOChannelFile impl will support io_pwritev callback,
but not all the FDs it can use will support seeking.
Same check for preadv
> +
> + return klass->io_pwritev(ioc, iov, niov, offset, errp);
> +}
> +
> +ssize_t qio_channel_io_preadv(QIOChannel *ioc, const struct iovec *iov,
> + size_t niov, off_t offset, Error **errp)
> +{
> + QIOChannelClass *klass = QIO_CHANNEL_GET_CLASS(ioc);
> +
> + if (!klass->io_preadv) {
> + error_setg(errp, "Channel does not support preadv");
> + return -1;
> + }
> +
> + return klass->io_preadv(ioc, iov, niov, offset, errp);
> +}
> +
> int qio_channel_shutdown(QIOChannel *ioc,
> QIOChannelShutdown how,
> Error **errp)
> --
> 2.34.1
>
With regards,
Daniel
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- Re: [PATCH v3 04/14] io: Add generic pwritev/preadv interface,
Daniel P . Berrangé <=