Fixed rudimentary suspend/resume.

This patch replaces the failing asynchronous I/O code in the qcow2
driver with a working synchronous implementation and fixes another
minor bug in iteration over QField structs. As a result, the VM can
now be suspended and resumed with the savevm and loadvm commands,
albeit with the following (major) caveats:

 1. The ADBd and other network services do not resume correctly.
 2. Normal SD card usage is blocked, since snapshots are written to a
    qcow2 image that must (for now) be mounted on hda.
 3. Resume only works after the emulator is fully booted. It is not
    (yet) possible to load an image immediately after the machine
    started.

The synchronous I/O code is ported from commit ef845c3b in mainline
QEMU, which addresses a similar issue. Further upstream mainline also
introduces a fix for the async I/O, but that patch is quite involved,
and for now this relatively simple fix works.

Change-Id: I660c19c22316aecdd7dcae357e66da20e0ab6d80

1 files changed, 9 insertions, 3 deletions

diff --git a/block/qcow2-cluster.c b/block/qcow2-cluster.c
index d349655..fdedf17 100644
--- a/block/qcow2-cluster.c
+++ b/block/qcow2-cluster.c
@@ -306,8 +306,8 @@ void qcow2_encrypt_sectors(BDRVQcowState *s, int64_t sector_num,
 }
 
 
-static int qcow_read(BlockDriverState *bs, int64_t sector_num,
-                     uint8_t *buf, int nb_sectors)
+int qcow2_read(BlockDriverState *bs, int64_t sector_num, uint8_t *buf,
+    int nb_sectors)
 {
     BDRVQcowState *s = bs->opaque;
     int ret, index_in_cluster, n, n1;
@@ -358,7 +358,7 @@ static int copy_sectors(BlockDriverState *bs, uint64_t start_sect,
     n = n_end - n_start;
     if (n <= 0)
         return 0;
-    ret = qcow_read(bs, start_sect + n_start, s->cluster_data, n);
+    ret = qcow2_read(bs, start_sect + n_start, s->cluster_data, n);
     if (ret < 0)
         return ret;
     if (s->crypt_method) {
@@ -732,6 +732,12 @@ uint64_t qcow2_alloc_cluster_offset(BlockDriverState *bs,
     }
     nb_clusters = i;
 
+    if (!nb_clusters) {
+        abort();
+    }
+
+    QLIST_INSERT_HEAD(&s->cluster_allocs, m, next_in_flight);
+
     /* allocate a new cluster */
 
     cluster_offset = qcow2_alloc_clusters(bs, nb_clusters * s->cluster_size);