From: "Dr. David Alan Gilbert" <dgilb...@redhat.com>
Postcopy needs a method to send messages from the destination back to
the source, this is the 'return path'.
Wire it up for 'socket' QEMUFile's using a dup'd fd.
Signed-off-by: Dr. David Alan Gilbert <dgilb...@redhat.com>
---
include/migration/qemu-file.h | 8 +++++
qemu-file.c | 74 +++++++++++++++++++++++++++++++++++++++----
2 files changed, 76 insertions(+), 6 deletions(-)
diff --git a/include/migration/qemu-file.h b/include/migration/qemu-file.h
index df38646..ec1a342 100644
--- a/include/migration/qemu-file.h
+++ b/include/migration/qemu-file.h
@@ -87,6 +87,11 @@ typedef size_t (QEMURamSaveFunc)(QEMUFile *f, void *opaque,
#define QEMUFILE_IO_BUF_SIZE 32768
#define QEMUFILE_MAX_IOV_SIZE MIN(IOV_MAX, 64)
+/*
+ * Return a QEMUFile for comms in the opposite direction
+ */
+typedef QEMUFile *(QEMURetPathFunc)(void *opaque);
+
typedef struct QEMUFileOps {
QEMUFilePutBufferFunc *put_buffer;
QEMUFileGetBufferFunc *get_buffer;
@@ -97,6 +102,7 @@ typedef struct QEMUFileOps {
QEMURamHookFunc *after_ram_iterate;
QEMURamHookFunc *hook_ram_load;
QEMURamSaveFunc *save_page;
+ QEMURetPathFunc *get_return_path;
} QEMUFileOps;
struct QEMUFile {
@@ -117,6 +123,7 @@ struct QEMUFile {
int last_error;
+ struct QEMUFile *return_path;
MigrationIncomingState *mis;
};
@@ -202,6 +209,7 @@ void qemu_file_set_rate_limit(QEMUFile *f, int64_t
new_rate);
int64_t qemu_file_get_rate_limit(QEMUFile *f);
int qemu_file_get_error(QEMUFile *f);
void qemu_file_set_error(QEMUFile *f, int ret);
+QEMUFile *qemu_file_get_return_path(QEMUFile *f);
void qemu_fflush(QEMUFile *f);
static inline void qemu_put_be64s(QEMUFile *f, const uint64_t *pv)
diff --git a/qemu-file.c b/qemu-file.c
index 88cacc7..98a6d2a 100644
--- a/qemu-file.c
+++ b/qemu-file.c
@@ -16,6 +16,54 @@ typedef struct QEMUFileSocket {
QEMUFile *file;
} QEMUFileSocket;
+/* Give a QEMUFile* off the same socket but data in the opposite
+ * direction.
+ * qemu_fopen_socket marks write fd's as blocking, but doesn't
+ * touch read fd's status, so we dup the fd just to keep settings
+ * separate. [TBD: Do I need to explicitly mark as non-block on read?]
+ */
+static QEMUFile *socket_dup_return_path(void *opaque)
+{
+ QEMUFileSocket *qfs = opaque;
+ int revfd;
+ bool this_is_read;
+ QEMUFile *result;
+
+ /* If it's already open, return it */
+ if (qfs->file->return_path) {
+ return qfs->file->return_path;
+ }
+
+ if (qemu_file_get_error(qfs->file)) {
+ /* If the forward file is in error, don't try and open a return */
+ return NULL;
+ }
+
+ /* I don't think there's a better way to tell which direction 'this' is */
+ this_is_read = qfs->file->ops->get_buffer != NULL;
+
+ revfd = dup(qfs->fd);
+ if (revfd == -1) {
+ error_report("Error duplicating fd for return path: %s",
+ strerror(errno));
+ return NULL;
+ }
+
+ qemu_set_nonblock(revfd);
+ result = qemu_fopen_socket(revfd, this_is_read ? "wb" : "rb");
+ qfs->file->return_path = result;
+
+ if (result) {
+ /* We are the reverse path of our reverse path (although I don't
+ expect this to be used, it would stop another dup if it was */
+ result->return_path = qfs->file;
+ } else {
+ close(revfd);
+ }
+
+ return result;
+}
+
static ssize_t socket_writev_buffer(void *opaque, struct iovec *iov, int
iovcnt,
int64_t pos)
{
@@ -313,17 +361,31 @@ QEMUFile *qemu_fdopen(int fd, const char *mode)
}
static const QEMUFileOps socket_read_ops = {
- .get_fd = socket_get_fd,
- .get_buffer = socket_get_buffer,
- .close = socket_close
+ .get_fd = socket_get_fd,
+ .get_buffer = socket_get_buffer,
+ .close = socket_close,
+ .get_return_path = socket_dup_return_path
};
static const QEMUFileOps socket_write_ops = {
- .get_fd = socket_get_fd,
- .writev_buffer = socket_writev_buffer,
- .close = socket_close
+ .get_fd = socket_get_fd,
+ .writev_buffer = socket_writev_buffer,
+ .close = socket_close,
+ .get_return_path = socket_dup_return_path
};
+/*
+ * Result: QEMUFile* for a 'return path' for comms in the opposite direction
+ * NULL if not available
+ */
+QEMUFile *qemu_file_get_return_path(QEMUFile *f)
+{
+ if (!f->ops->get_return_path) {
+ return NULL;
+ }
+ return f->ops->get_return_path(f->opaque);
+}
+
bool qemu_file_mode_is_not_valid(const char *mode)
{
if (mode == NULL ||
--
1.9.3
