migration: move rate limiting to QEMUFile

Rate limiting is now simply a byte counter; client call
qemu_file_rate_limit() manually to determine if they have to exit.
So it is possible and simple to move the functionality to QEMUFile.

This makes the remaining functionality of s->file redundant;
in the next patch we can remove it and write directly to s->migration_file.

Reviewed-by: Orit Wasserman <owasserm@redhat.com>
Reviewed-by: Juan Quintela <quintela@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Juan Quintela <quintela@redhat.com>

docs/migration.txt

@@ -55,10 +55,7 @@ QEMUFile with:
 QEMUFile *qemu_fopen_ops(void *opaque,
                          QEMUFilePutBufferFunc *put_buffer,
                          QEMUFileGetBufferFunc *get_buffer,
-                         QEMUFileCloseFunc *close,
-                         QEMUFileRateLimit *rate_limit,
-                         QEMUFileSetRateLimit *set_rate_limit,
-                         QEMUFileGetRateLimit *get_rate_limit);
+                         QEMUFileCloseFunc *close);
 
 The functions have the following functionality:
 
@@ -80,24 +77,9 @@ Close a file and return an error code.
 
 typedef int (QEMUFileCloseFunc)(void *opaque);
 
-Called to determine if the file has exceeded its bandwidth allocation.  The
-bandwidth capping is a soft limit, not a hard limit.
-
-typedef int (QEMUFileRateLimit)(void *opaque);
-
-Called to change the current bandwidth allocation. This function must return
-the new actual bandwidth. It should be new_rate if everything goes OK, and
-the old rate otherwise.
-
-typedef size_t (QEMUFileSetRateLimit)(void *opaque, size_t new_rate);
-typedef size_t (QEMUFileGetRateLimit)(void *opaque);
-
 You can use any internal state that you need using the opaque void *
 pointer that is passed to all functions.
 
-The rate limiting functions are used to limit the bandwidth used by
-QEMU migration.
-
 The important functions for us are put_buffer()/get_buffer() that
 allow to write/read a buffer into the QEMUFile.
 

include/migration/qemu-file.h

@@ -51,26 +51,11 @@ typedef int (QEMUFileCloseFunc)(void *opaque);
  */
 typedef int (QEMUFileGetFD)(void *opaque);
 
-/* Called to determine if the file has exceeded its bandwidth allocation.  The
- * bandwidth capping is a soft limit, not a hard limit.
- */
-typedef int (QEMUFileRateLimit)(void *opaque);
-
-/* Called to change the current bandwidth allocation. This function must return
- * the new actual bandwidth. It should be new_rate if everything goes ok, and
- * the old rate otherwise
- */
-typedef int64_t (QEMUFileSetRateLimit)(void *opaque, int64_t new_rate);
-typedef int64_t (QEMUFileGetRateLimit)(void *opaque);
-
 typedef struct QEMUFileOps {
     QEMUFilePutBufferFunc *put_buffer;
     QEMUFileGetBufferFunc *get_buffer;
     QEMUFileCloseFunc *close;
     QEMUFileGetFD *get_fd;
-    QEMUFileRateLimit *rate_limit;
-    QEMUFileSetRateLimit *set_rate_limit;
-    QEMUFileGetRateLimit *get_rate_limit;
 } QEMUFileOps;
 
 QEMUFile *qemu_fopen_ops(void *opaque, const QEMUFileOps *ops);
@@ -109,7 +94,8 @@ unsigned int qemu_get_be32(QEMUFile *f);
 uint64_t qemu_get_be64(QEMUFile *f);
 
 int qemu_file_rate_limit(QEMUFile *f);
-int64_t qemu_file_set_rate_limit(QEMUFile *f, int64_t new_rate);
+void qemu_file_reset_rate_limit(QEMUFile *f);
+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);
 

migration.c

@@ -518,7 +518,6 @@ static int migration_put_buffer(void *opaque, const uint8_t *buf,
         return ret;
     }
 
-    s->bytes_xfer += size;
     return size;
 }
 
@@ -543,49 +542,6 @@ static int migration_get_fd(void *opaque)
     return qemu_get_fd(s->migration_file);
 }
 
-/*
- * The meaning of the return values is:
- *   0: We can continue sending
- *   1: Time to stop
- *   negative: There has been an error
- */
-static int migration_rate_limit(void *opaque)
-{
-    MigrationState *s = opaque;
-    int ret;
-
-    ret = qemu_file_get_error(s->file);
-    if (ret) {
-        return ret;
-    }
-
-    if (s->bytes_xfer >= s->xfer_limit) {
-        return 1;
-    }
-
-    return 0;
-}
-
-static int64_t migration_set_rate_limit(void *opaque, int64_t new_rate)
-{
-    MigrationState *s = opaque;
-    if (qemu_file_get_error(s->file)) {
-        goto out;
-    }
-
-    s->xfer_limit = new_rate;
-
-out:
-    return s->xfer_limit;
-}
-
-static int64_t migration_get_rate_limit(void *opaque)
-{
-    MigrationState *s = opaque;
-
-    return s->xfer_limit;
-}
-
 static void *migration_thread(void *opaque)
 {
     MigrationState *s = opaque;
@@ -646,7 +602,7 @@ static void *migration_thread(void *opaque)
                 s->expected_downtime = s->dirty_bytes_rate / bandwidth;
             }
 
-            s->bytes_xfer = 0;
+            qemu_file_reset_rate_limit(s->file);
             sleep_time = 0;
             initial_time = current_time;
             initial_bytes = qemu_ftell(s->file);
@@ -679,9 +635,6 @@ static const QEMUFileOps migration_file_ops = {
     .get_fd =         migration_get_fd,
     .put_buffer =     migration_put_buffer,
     .close =          migration_close,
-    .rate_limit =     migration_rate_limit,
-    .get_rate_limit = migration_get_rate_limit,
-    .set_rate_limit = migration_set_rate_limit,
 };
 
 void migrate_fd_connect(MigrationState *s)
@@ -689,10 +642,8 @@ void migrate_fd_connect(MigrationState *s)
     s->state = MIG_STATE_ACTIVE;
     trace_migrate_set_state(MIG_STATE_ACTIVE);
 
-    s->bytes_xfer = 0;
     /* This is a best 1st approximation. ns to ms */
     s->expected_downtime = max_downtime/1000000;
-
     s->cleanup_bh = qemu_bh_new(migrate_fd_cleanup, s);
     s->file = qemu_fopen_ops(s, &migration_file_ops);
 

savevm.c

@@ -119,6 +119,9 @@ struct QEMUFile {
     void *opaque;
     int is_write;
 
+    int64_t bytes_xfer;
+    int64_t xfer_limit;
+
     int64_t pos; /* start of buffer when writing, end of buffer
                     when reading */
     int buf_index;
@@ -479,7 +482,6 @@ QEMUFile *qemu_fopen_ops(void *opaque, const QEMUFileOps *ops)
     f->opaque = opaque;
     f->ops = ops;
     f->is_write = 0;
-
     return f;
 }
 
@@ -605,6 +607,7 @@ void qemu_put_buffer(QEMUFile *f, const uint8_t *buf, int size)
         memcpy(f->buf + f->buf_index, buf, l);
         f->is_write = 1;
         f->buf_index += l;
+        f->bytes_xfer += l;
         buf += l;
         size -= l;
         if (f->buf_index >= IO_BUF_SIZE) {
@@ -725,28 +728,28 @@ int64_t qemu_ftell(QEMUFile *f)
 
 int qemu_file_rate_limit(QEMUFile *f)
 {
-    if (f->ops->rate_limit)
-        return f->ops->rate_limit(f->opaque);
-
+    if (qemu_file_get_error(f)) {
+        return 1;
+    }
+    if (f->xfer_limit > 0 && f->bytes_xfer > f->xfer_limit) {
+        return 1;
+    }
     return 0;
 }
 
 int64_t qemu_file_get_rate_limit(QEMUFile *f)
 {
-    if (f->ops->get_rate_limit)
-        return f->ops->get_rate_limit(f->opaque);
-
-    return 0;
+    return f->xfer_limit;
 }
 
-int64_t qemu_file_set_rate_limit(QEMUFile *f, int64_t new_rate)
+void qemu_file_set_rate_limit(QEMUFile *f, int64_t limit)
 {
-    /* any failed or completed migration keeps its state to allow probing of
-     * migration data, but has no associated file anymore */
-    if (f && f->ops->set_rate_limit)
-        return f->ops->set_rate_limit(f->opaque, new_rate);
+    f->xfer_limit = limit;
+}
 
-    return 0;
+void qemu_file_reset_rate_limit(QEMUFile *f)
+{
+    f->bytes_xfer = 0;
 }
 
 void qemu_put_be16(QEMUFile *f, unsigned int v)