[v10,04/12] migration/qemu-file: Add qemu_file_get_to_fd()

Commit Message

Avihai Horon Feb. 9, 2023, 7:20 p.m. UTC

Add new function qemu_file_get_to_fd() that allows reading data from
QEMUFile and writing it straight into a given fd.

This will be used later in VFIO migration code.

Signed-off-by: Avihai Horon <[e-mail]>
Reviewed-by: Vladimir Sementsov-Ogievskiy <[e-mail]>
Reviewed-by: Cédric Le Goater <[e-mail]>
---
 migration/qemu-file.h |  1 +
 migration/qemu-file.c | 34 ++++++++++++++++++++++++++++++++++
 2 files changed, 35 insertions(+)

Comments

Alex Williamson Feb. 9, 2023, 11:50 p.m. UTC | #1

Hey Juan,

I think we're close, please ack this if it looks ok.  Thanks,

Alex

On Thu, 9 Feb 2023 21:20:35 +0200
Avihai Horon <[e-mail]> wrote:

> Add new function qemu_file_get_to_fd() that allows reading data from
> QEMUFile and writing it straight into a given fd.
> 
> This will be used later in VFIO migration code.
> 
> Signed-off-by: Avihai Horon <[e-mail]>
> Reviewed-by: Vladimir Sementsov-Ogievskiy <[e-mail]>
> Reviewed-by: Cédric Le Goater <[e-mail]>
> ---
>  migration/qemu-file.h |  1 +
>  migration/qemu-file.c | 34 ++++++++++++++++++++++++++++++++++
>  2 files changed, 35 insertions(+)
> 
> diff --git a/migration/qemu-file.h b/migration/qemu-file.h
> index fa13d04d78..9d0155a2a1 100644
> --- a/migration/qemu-file.h
> +++ b/migration/qemu-file.h
> @@ -148,6 +148,7 @@ int qemu_file_shutdown(QEMUFile *f);
>  QEMUFile *qemu_file_get_return_path(QEMUFile *f);
>  void qemu_fflush(QEMUFile *f);
>  void qemu_file_set_blocking(QEMUFile *f, bool block);
> +int qemu_file_get_to_fd(QEMUFile *f, int fd, size_t size);
>  
>  void ram_control_before_iterate(QEMUFile *f, uint64_t flags);
>  void ram_control_after_iterate(QEMUFile *f, uint64_t flags);
> diff --git a/migration/qemu-file.c b/migration/qemu-file.c
> index 2d5f74ffc2..102ab3b439 100644
> --- a/migration/qemu-file.c
> +++ b/migration/qemu-file.c
> @@ -940,3 +940,37 @@ QIOChannel *qemu_file_get_ioc(QEMUFile *file)
>  {
>      return file->ioc;
>  }
> +
> +/*
> + * Read size bytes from QEMUFile f and write them to fd.
> + */
> +int qemu_file_get_to_fd(QEMUFile *f, int fd, size_t size)
> +{
> +    while (size) {
> +        size_t pending = f->buf_size - f->buf_index;
> +        ssize_t rc;
> +
> +        if (!pending) {
> +            rc = qemu_fill_buffer(f);
> +            if (rc < 0) {
> +                return rc;
> +            }
> +            if (rc == 0) {
> +                return -EIO;
> +            }
> +            continue;
> +        }
> +
> +        rc = write(fd, f->buf + f->buf_index, MIN(pending, size));
> +        if (rc < 0) {
> +            return -errno;
> +        }
> +        if (rc == 0) {
> +            return -EIO;
> +        }
> +        f->buf_index += rc;
> +        size -= rc;
> +    }
> +
> +    return 0;
> +}

Juan Quintela Feb. 15, 2023, 7:33 a.m. UTC | #2

Avihai Horon <[e-mail]> wrote:
> Add new function qemu_file_get_to_fd() that allows reading data from
> QEMUFile and writing it straight into a given fd.
>
> This will be used later in VFIO migration code.
>
> Signed-off-by: Avihai Horon <[e-mail]>
> Reviewed-by: Vladimir Sementsov-Ogievskiy <[e-mail]>
> Reviewed-by: Cédric Le Goater <[e-mail]>

Reviewed-by: Juan Quintela <[e-mail]>

Patch

diff --git a/migration/qemu-file.h b/migration/qemu-file.h
index fa13d04d78..9d0155a2a1 100644
--- a/migration/qemu-file.h
+++ b/migration/qemu-file.h
@@ -148,6 +148,7 @@  int qemu_file_shutdown(QEMUFile *f);
 QEMUFile *qemu_file_get_return_path(QEMUFile *f);
 void qemu_fflush(QEMUFile *f);
 void qemu_file_set_blocking(QEMUFile *f, bool block);
+int qemu_file_get_to_fd(QEMUFile *f, int fd, size_t size);
 
 void ram_control_before_iterate(QEMUFile *f, uint64_t flags);
 void ram_control_after_iterate(QEMUFile *f, uint64_t flags);
diff --git a/migration/qemu-file.c b/migration/qemu-file.c
index 2d5f74ffc2..102ab3b439 100644
--- a/migration/qemu-file.c
+++ b/migration/qemu-file.c
@@ -940,3 +940,37 @@  QIOChannel *qemu_file_get_ioc(QEMUFile *file)
 {
     return file->ioc;
 }
+
+/*
+ * Read size bytes from QEMUFile f and write them to fd.
+ */
+int qemu_file_get_to_fd(QEMUFile *f, int fd, size_t size)
+{
+    while (size) {
+        size_t pending = f->buf_size - f->buf_index;
+        ssize_t rc;
+
+        if (!pending) {
+            rc = qemu_fill_buffer(f);
+            if (rc < 0) {
+                return rc;
+            }
+            if (rc == 0) {
+                return -EIO;
+            }
+            continue;
+        }
+
+        rc = write(fd, f->buf + f->buf_index, MIN(pending, size));
+        if (rc < 0) {
+            return -errno;
+        }
+        if (rc == 0) {
+            return -EIO;
+        }
+        f->buf_index += rc;
+        size -= rc;
+    }
+
+    return 0;
+}