[PATCH v3 05/14] io: implement io_pwritev for QIOChannelFile

[Nikolay Borisov]

The upcoming 'fixed-ram' feature would require qemu to write data at
specific offsets of the file. Add a minimal implementation of pwritev
and expose it via the io_pwritev interface.

Signed-off-by: Nikolay Borisov <nborisov@suse.com>
---
 io/channel-file.c | 25 +++++++++++++++++++++++++
 1 file changed, 25 insertions(+)

diff --git a/io/channel-file.c b/io/channel-file.c
index b67687c2aa64..a7a90c12dc2b 100644
--- a/io/channel-file.c
+++ b/io/channel-file.c
@@ -136,6 +136,30 @@ static ssize_t qio_channel_file_writev(QIOChannel *ioc,
     return ret;
 }
 
+static ssize_t qio_channel_file_pwritev(QIOChannel *ioc,
+                                        const struct iovec *iov,
+                                        size_t niov,
+                                        off_t offset,
+                                        Error **errp)
+{
+    QIOChannelFile *fioc = QIO_CHANNEL_FILE(ioc);
+    ssize_t ret;
+
+ retry:
+    ret = pwritev(fioc->fd, iov, niov, offset);
+    if (ret <= 0) {
+        if (errno == EAGAIN) {
+            return QIO_CHANNEL_ERR_BLOCK;
+        }
+        if (errno == EINTR) {
+            goto retry;
+        }
+        error_setg_errno(errp, errno, "Unable to write to file");
+        return -1;
+    }
+    return ret;
+}
+
 static int qio_channel_file_set_blocking(QIOChannel *ioc,
                                          bool enabled,
                                          Error **errp)
@@ -218,6 +242,7 @@ static void qio_channel_file_class_init(ObjectClass *klass,
     ioc_klass->io_writev = qio_channel_file_writev;
     ioc_klass->io_readv = qio_channel_file_readv;
     ioc_klass->io_set_blocking = qio_channel_file_set_blocking;
+    ioc_klass->io_pwritev = qio_channel_file_pwritev;
     ioc_klass->io_seek = qio_channel_file_seek;
     ioc_klass->io_close = qio_channel_file_close;
     ioc_klass->io_create_watch = qio_channel_file_create_watch;
-- 
2.34.1