[Qemu-devel] [PATCH v1] add new function to copy dirty-bitmap

[Qemu-devel] [PATCH v1] add new function to copy dirty-bitmap

[mahaocong]

From: mahaocong <mahaocong@didichuxing.com>

This patch adds new function to copy the hbitmap from an exist dirty-bitmap to
another. The destination bitmap should have the same size and granularity with
the source bitmap, or the copy will fail.

Signed-off-by: mahaocong <mahaocong@didichuxing.com>
---
 block/dirty-bitmap.c         | 14 ++++++++++++++
 include/block/dirty-bitmap.h |  3 +++
 include/qemu/hbitmap.h       |  2 ++
 util/hbitmap.c               | 28 ++++++++++++++++++++++++++++
 4 files changed, 47 insertions(+)

diff --git a/block/dirty-bitmap.c b/block/dirty-bitmap.c
index 89fd1d7f8b..4445182e2a 100644
--- a/block/dirty-bitmap.c
+++ b/block/dirty-bitmap.c
@@ -348,6 +348,20 @@ BdrvDirtyBitmap *bdrv_reclaim_dirty_bitmap(BlockDriverState *bs,
     return ret;
 }
 
+BdrvDirtyBitmap *bdrv_copy_dirty_bitmap(BdrvDirtyBitmap *src,
+                                        BdrvDirtyBitmap *dest,
+                                        Error **errp)
+{
+    qemu_mutex_lock(src->mutex);
+    if (!hbitmap_copy(dest->bitmap, src->bitmap)) {
+        error_setg(errp, "Error: copy src bitmap failed");
+        return NULL;
+    }
+    qemu_mutex_unlock(src->mutex);
+
+    return dest;
+}
+
 /**
  * Truncates _all_ bitmaps attached to a BDS.
  * Called with BQL taken.
diff --git a/include/block/dirty-bitmap.h b/include/block/dirty-bitmap.h
index 8f38a3dec1..ae2e82f44b 100644
--- a/include/block/dirty-bitmap.h
+++ b/include/block/dirty-bitmap.h
@@ -21,6 +21,9 @@ BdrvDirtyBitmap *bdrv_dirty_bitmap_abdicate(BlockDriverState *bs,
 BdrvDirtyBitmap *bdrv_reclaim_dirty_bitmap(BlockDriverState *bs,
                                            BdrvDirtyBitmap *bitmap,
                                            Error **errp);
+BdrvDirtyBitmap *bdrv_copy_dirty_bitmap(BdrvDirtyBitmap *src,
+                                        BdrvDirtyBitmap *dest,
+                                        Error **errp);
 void bdrv_dirty_bitmap_enable_successor(BdrvDirtyBitmap *bitmap);
 BdrvDirtyBitmap *bdrv_find_dirty_bitmap(BlockDriverState *bs,
                                         const char *name);
diff --git a/include/qemu/hbitmap.h b/include/qemu/hbitmap.h
index a7cb780592..6de3b4eb7e 100644
--- a/include/qemu/hbitmap.h
+++ b/include/qemu/hbitmap.h
@@ -91,6 +91,8 @@ bool hbitmap_merge(const HBitmap *a, const HBitmap *b, HBitmap *result);
  */
 bool hbitmap_can_merge(const HBitmap *a, const HBitmap *b);
 
+bool hbitmap_copy(HBitmap *dst, const HBitmap *src);
+
 /**
  * hbitmap_empty:
  * @hb: HBitmap to operate on.
diff --git a/util/hbitmap.c b/util/hbitmap.c
index 8d402c59d9..7ae2fc270c 100644
--- a/util/hbitmap.c
+++ b/util/hbitmap.c
@@ -765,6 +765,34 @@ bool hbitmap_merge(const HBitmap *a, const HBitmap *b, HBitmap *result)
     return true;
 }
 
+/*
+ * Copy HBitmaps form src to dst.
+ *
+ * @return true if the copy was successful,
+ *         false if it was not attempted.
+ */
+bool hbitmap_copy(HBitmap *dst, const HBitmap *src)
+{
+    int i;
+
+    if ((dst->size != src->size) || (dst->granularity != src->granularity)) {
+        return false;
+    }
+
+    if (hbitmap_count(src) == 0) {
+        return true;
+    }
+
+    for (i = HBITMAP_LEVELS - 1; i >= 0; i--) {
+        memcpy(dst->levels[i], src->levels[i],
+               src->sizes[i] * sizeof(unsigned long));
+    }
+
+    dst->count = src->count;
+    return true;
+}
+
+
 HBitmap *hbitmap_create_meta(HBitmap *hb, int chunk_size)
 {
     assert(!(chunk_size & (chunk_size - 1)));
-- 
2.14.1

Re: [Qemu-devel] [PATCH v1] add new function to copy dirty-bitmap

[Eric Blake]

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On 1/2/19 4:01 AM, mahaocong wrote:
> From: mahaocong <mahaocong@didichuxing.com>
> 
> This patch adds new function to copy the hbitmap from an exist dirty-bitmap to
> another. The destination bitmap should have the same size and granularity with
> the source bitmap, or the copy will fail.

Is there a client in mind for this new code?  And how does it differ to
what you can already achieve by the combination of
bdrv_clear_dirty_bitmap/bdrv_merge_dirty_bitmap?

> 
> Signed-off-by: mahaocong <mahaocong@didichuxing.com>

Typical S-o-b and git authorship uses a preferred legal name rather than
a single-word username (there have been exceptions made in the past, but
we try not to introduce more without good reason).  You can also teach
git to spell your name in both native UTF-8 characters and a Latinized
form, if you prefer.

-- 
Eric Blake, Principal Software Engineer
Red Hat, Inc.           +1-919-301-3226
Virtualization:  qemu.org | libvirt.org


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Re: [Qemu-devel] [PATCH v1] add new function to copy dirty-bitmap

[John Snow]

On 1/2/19 5:01 AM, mahaocong wrote:
> From: mahaocong <mahaocong@didichuxing.com>
> 
> This patch adds new function to copy the hbitmap from an exist dirty-bitmap to
> another. The destination bitmap should have the same size and granularity with
> the source bitmap, or the copy will fail.
> 
> Signed-off-by: mahaocong <mahaocong@didichuxing.com>

/technically/ we *can* do this already by creating a blank bitmap and
merging from one bitmap to the empty one.

Do you have a good argument for why copy is needed in addition?

--js