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Re: [PATCH v2 18/21] migration: remove the QEMUFileOps 'get_buffer' call
From: |
Dr. David Alan Gilbert |
Subject: |
Re: [PATCH v2 18/21] migration: remove the QEMUFileOps 'get_buffer' callback |
Date: |
Mon, 27 Jun 2022 13:04:45 +0100 |
User-agent: |
Mutt/2.2.6 (2022-06-05) |
* Daniel P. Berrangé (berrange@redhat.com) wrote:
> This directly implements the get_buffer logic using QIOChannel APIs.
>
> Reviewed-by: Dr. David Alan Gilbert <dgilbert@redhat.com>
> Signed-off-by: Daniel P. Berrangé <berrange@redhat.com>
Coverity is pointing out a fun deadcode path from this:
> diff --git a/migration/qemu-file.c b/migration/qemu-file.c
> index 5eb8cf0e28..df438724cd 100644
> --- a/migration/qemu-file.c
> +++ b/migration/qemu-file.c
> @@ -377,8 +377,22 @@ static ssize_t qemu_fill_buffer(QEMUFile *f)
> return 0;
> }
>
> - len = f->ops->get_buffer(f->ioc, f->buf + pending, f->total_transferred,
> - IO_BUF_SIZE - pending, &local_error);
> + do {
> + len = qio_channel_read(f->ioc,
> + (char *)f->buf + pending,
> + IO_BUF_SIZE - pending,
> + &local_error);
> + if (len == QIO_CHANNEL_ERR_BLOCK) {
> + if (qemu_in_coroutine()) {
> + qio_channel_yield(f->ioc, G_IO_IN);
> + } else {
> + qio_channel_wait(f->ioc, G_IO_IN);
> + }
> + } else if (len < 0) {
> + len = EIO;
> + }
> + } while (len == QIO_CHANNEL_ERR_BLOCK);
> +
the next code is:
if (len > 0) {
f->buf_size += len;
f->total_transferred += len;
} else if (len == 0) {
qemu_file_set_error_obj(f, -EIO, local_error);
} else if (len != -EAGAIN) {
qemu_file_set_error_obj(f, len, local_error);
} else {
**** error_free(local_error);
}
because of the while loop, we should never actually see
len = QIO_CHANNEL_ERR_BLOCK out of the bottom; so the only
error value we should have is -EIO; so that error_free is
not hittable.
Dave
> if (len > 0) {
> f->buf_size += len;
> f->total_transferred += len;
> diff --git a/migration/qemu-file.h b/migration/qemu-file.h
> index 4a3beedb5b..f7ed568894 100644
> --- a/migration/qemu-file.h
> +++ b/migration/qemu-file.h
> @@ -29,14 +29,6 @@
> #include "exec/cpu-common.h"
> #include "io/channel.h"
>
> -/* Read a chunk of data from a file at the given position. The pos argument
> - * can be ignored if the file is only be used for streaming. The number of
> - * bytes actually read should be returned.
> - */
> -typedef ssize_t (QEMUFileGetBufferFunc)(void *opaque, uint8_t *buf,
> - int64_t pos, size_t size,
> - Error **errp);
> -
> /*
> * This function writes an iovec to file. The handler must write all
> * of the data or return a negative errno value.
> @@ -77,7 +69,6 @@ typedef size_t (QEMURamSaveFunc)(QEMUFile *f,
> typedef QEMUFile *(QEMURetPathFunc)(void *opaque);
>
> typedef struct QEMUFileOps {
> - QEMUFileGetBufferFunc *get_buffer;
> QEMUFileWritevBufferFunc *writev_buffer;
> QEMURetPathFunc *get_return_path;
> } QEMUFileOps;
> --
> 2.36.1
>
--
Dr. David Alan Gilbert / dgilbert@redhat.com / Manchester, UK
- [PATCH v2 15/21] migration: remove the QEMUFileOps 'shut_down' callback, (continued)
- [PATCH v2 15/21] migration: remove the QEMUFileOps 'shut_down' callback, Daniel P . Berrangé, 2022/06/20
- [PATCH v2 09/21] migration: introduce a QIOChannel impl for BlockDriverState VMState, Daniel P . Berrangé, 2022/06/20
- [PATCH v2 14/21] migration: remove unused QEMUFileGetFD typedef / qemu_get_fd method, Daniel P . Berrangé, 2022/06/20
- [PATCH v2 18/21] migration: remove the QEMUFileOps 'get_buffer' callback, Daniel P . Berrangé, 2022/06/20
- [PATCH v2 16/21] migration: remove the QEMUFileOps 'set_blocking' callback, Daniel P . Berrangé, 2022/06/20
- [PATCH v2 19/21] migration: remove the QEMUFileOps 'writev_buffer' callback, Daniel P . Berrangé, 2022/06/20
- [PATCH v2 20/21] migration: remove the QEMUFileOps 'get_return_path' callback, Daniel P . Berrangé, 2022/06/20
- [PATCH v2 21/21] migration: remove the QEMUFileOps abstraction, Daniel P . Berrangé, 2022/06/20
- [PATCH v2 08/21] migration: rename qemu_file_update_transfer to qemu_file_acct_rate_limit, Daniel P . Berrangé, 2022/06/20