From patchwork Wed Oct 17 16:00:23 2012
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Subject: [RFC, V2,
 14/20] qcow2: Extract qcow2_add_feature and qcow2_remove_feature.
From: =?utf-8?q?Beno=C3=AEt_Canet?= <benoit@irqsave.net>
X-Patchwork-Id: 192105
Message-Id: <1350489629-1838-15-git-send-email-benoit@irqsave.net>
To: qemu-devel@nongnu.org
Cc: kwolf@redhat.com, =?UTF-8?q?Beno=C3=AEt=20Canet?= <benoit@irqsave.net>, 
 stefanha@redhat.com
Date: Wed, 17 Oct 2012 18:00:23 +0200

These functions will be use to mark that deduplication is activatedi
on an image.

---
block/qcow2.c |   40 +++++++++++++++++++++++++++-------------
 block/qcow2.h |    4 ++--
 2 files changed, 29 insertions(+), 15 deletions(-)

diff --git a/block/qcow2.c b/block/qcow2.c
index 18cb85d..b11b6a7 100644
--- a/block/qcow2.c
+++ b/block/qcow2.c
@@ -235,13 +235,14 @@ static void report_unsupported_feature(BlockDriverState *bs,
 }
 
 /*
- * Sets the dirty bit and flushes afterwards if necessary.
+ * Sets the an incompatible feature bit and flushes afterwards if necessary.
  *
  * The incompatible_features bit is only set if the image file header was
  * updated successfully.  Therefore it is not required to check the return
  * value of this function.
  */
-static int qcow2_mark_dirty(BlockDriverState *bs)
+static int qcow2_add_feature(BlockDriverState *bs,
+                             QCow2IncompatibleFeature feature)
 {
     BDRVQcowState *s = bs->opaque;
     uint64_t val;
@@ -249,11 +250,11 @@ static int qcow2_mark_dirty(BlockDriverState *bs)
 
     assert(s->qcow_version >= 3);
 
-    if (s->incompatible_features & QCOW2_INCOMPAT_DIRTY) {
-        return 0; /* already dirty */
+    if (s->incompatible_features & feature) {
+        return 0; /* already added */
     }
 
-    val = cpu_to_be64(s->incompatible_features | QCOW2_INCOMPAT_DIRTY);
+    val = cpu_to_be64(s->incompatible_features | feature);
     ret = bdrv_pwrite(bs->file, offsetof(QCowHeader, incompatible_features),
                       &val, sizeof(val));
     if (ret < 0) {
@@ -264,32 +265,45 @@ static int qcow2_mark_dirty(BlockDriverState *bs)
         return ret;
     }
 
-    /* Only treat image as dirty if the header was updated successfully */
-    s->incompatible_features |= QCOW2_INCOMPAT_DIRTY;
+    /* Only treat image as having the feature if the header was updated
+     * successfully
+     */
+    s->incompatible_features |= feature;
     return 0;
 }
 
+static int qcow2_mark_dirty(BlockDriverState *bs)
+{
+    return qcow2_add_feature(bs, QCOW2_INCOMPAT_DIRTY);
+}
+
 /*
- * Clears the dirty bit and flushes before if necessary.  Only call this
- * function when there are no pending requests, it does not guard against
- * concurrent requests dirtying the image.
+ * Clears an incompatible feature bit and flushes before if necessary.
+ * Only call this function when there are no pending requests, it does not
+ * guard against concurrent requests adding a feature to the image.
  */
-static int qcow2_mark_clean(BlockDriverState *bs)
+static int qcow2_remove_feature(BlockDriverState *bs,
+                             QCow2IncompatibleFeature feature)
 {
     BDRVQcowState *s = bs->opaque;
 
-    if (s->incompatible_features & QCOW2_INCOMPAT_DIRTY) {
+    if (s->incompatible_features & feature) {
         int ret = bdrv_flush(bs);
         if (ret < 0) {
             return ret;
         }
 
-        s->incompatible_features &= ~QCOW2_INCOMPAT_DIRTY;
+        s->incompatible_features &= ~feature;
         return qcow2_update_header(bs);
     }
     return 0;
 }
 
+static int qcow2_mark_clean(BlockDriverState *bs)
+{
+    return qcow2_remove_feature(bs, QCOW2_INCOMPAT_DIRTY);
+}
+
 static int qcow2_check(BlockDriverState *bs, BdrvCheckResult *result,
                        BdrvCheckMode fix)
 {
diff --git a/block/qcow2.h b/block/qcow2.h
index ba900e0..5ecea94 100644
--- a/block/qcow2.h
+++ b/block/qcow2.h
@@ -125,14 +125,14 @@ enum {
 };
 
 /* Incompatible feature bits */
-enum {
+typedef enum {
     QCOW2_INCOMPAT_DIRTY_BITNR   = 0,
     QCOW2_INCOMPAT_DIRTY         = 1 << QCOW2_INCOMPAT_DIRTY_BITNR,
     QCOW2_INCOMPAT_DEDUP_BITNR   = 1,
     QCOW2_INCOMPAT_DEDUP         = 1 << QCOW2_INCOMPAT_DEDUP_BITNR,
 
     QCOW2_INCOMPAT_MASK          = QCOW2_INCOMPAT_DIRTY | QCOW2_INCOMPAT_DEDUP,
-};
+} QCow2IncompatibleFeature;
 
 /* Compatible feature bits */
 enum {