[Qemu-devel] [PATCH 17/29] qcow2-bitmap: add autoclear bit

[Vladimir Sementsov-Ogievskiy]

Add autoclear bit for handling rewriting image by old qemu version.

If autoclear bit is not set, but bitmaps extension is found it
would not be loaded and warning will be generated.

Signed-off-by: Vladimir Sementsov-Ogievskiy <address@hidden>
---
 block/qcow2-bitmap.c |  4 ++++
 block/qcow2.c        | 12 ++++++++++--
 block/qcow2.h        |  9 +++++++++
 3 files changed, 23 insertions(+), 2 deletions(-)

diff --git a/block/qcow2-bitmap.c b/block/qcow2-bitmap.c
index 32f1a50..0e95121 100644
--- a/block/qcow2-bitmap.c
+++ b/block/qcow2-bitmap.c
@@ -479,6 +479,10 @@ static int directory_update(BlockDriverState *bs, uint8_t 
*new_dir,
         if (ret < 0) {
             goto fail;
         }
+
+        s->autoclear_features |= QCOW2_AUTOCLEAR_DIRTY_BITMAPS;
+    } else {
+        s->autoclear_features &= ~(uint64_t)QCOW2_AUTOCLEAR_DIRTY_BITMAPS;
     }
     s->bitmap_directory_offset = new_offset;
     s->bitmap_directory_size = new_size;
diff --git a/block/qcow2.c b/block/qcow2.c
index 60b0acb..76ad7c6 100644
--- a/block/qcow2.c
+++ b/block/qcow2.c
@@ -165,6 +165,13 @@ static int qcow2_read_extensions(BlockDriverState *bs, 
uint64_t start_offset,
             break;
 
         case QCOW2_EXT_MAGIC_DIRTY_BITMAPS:
+            if (!(s->autoclear_features & QCOW2_AUTOCLEAR_DIRTY_BITMAPS)) {
+                fprintf(stderr,
+                        "WARNING: bitmaps_ext: autoclear flag is not "
+                        "set, all bitmaps will be considered as inconsistent");
+                break;
+            }
+
             ret = bdrv_pread(bs->file, offset, &bitmaps_ext, ext.len);
             if (ret < 0) {
                 error_setg_errno(errp, -ret, "ERROR: bitmaps_ext: "
@@ -1206,8 +1213,9 @@ static int qcow2_open(BlockDriverState *bs, QDict 
*options, int flags,
     }
 
     /* Clear unknown autoclear feature bits */
-    if (!bs->read_only && !(flags & BDRV_O_INACTIVE) && s->autoclear_features) 
{
-        s->autoclear_features = 0;
+    if (!bs->read_only && !(flags & BDRV_O_INACTIVE) &&
+        (s->autoclear_features & ~QCOW2_AUTOCLEAR_MASK)) {
+        s->autoclear_features &= QCOW2_AUTOCLEAR_MASK;
         ret = qcow2_update_header(bs);
         if (ret < 0) {
             error_setg_errno(errp, -ret, "Could not update qcow2 header");
diff --git a/block/qcow2.h b/block/qcow2.h
index d4515fb..74d395b 100644
--- a/block/qcow2.h
+++ b/block/qcow2.h
@@ -215,6 +215,15 @@ enum {
     QCOW2_COMPAT_FEAT_MASK            = QCOW2_COMPAT_LAZY_REFCOUNTS,
 };
 
+/* Autoclear feature bits */
+enum {
+    QCOW2_AUTOCLEAR_DIRTY_BITMAPS_BITNR = 0,
+    QCOW2_AUTOCLEAR_DIRTY_BITMAPS       =
+        1 << QCOW2_AUTOCLEAR_DIRTY_BITMAPS_BITNR,
+
+    QCOW2_AUTOCLEAR_MASK                = QCOW2_AUTOCLEAR_DIRTY_BITMAPS,
+};
+
 enum qcow2_discard_type {
     QCOW2_DISCARD_NEVER = 0,
     QCOW2_DISCARD_ALWAYS,
-- 
1.8.3.1