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Re: [Qemu-block] [Qemu-devel] [PATCH 12/18] block/dirty-bitmap: Add bdrv


From: Vladimir Sementsov-Ogievskiy
Subject: Re: [Qemu-block] [Qemu-devel] [PATCH 12/18] block/dirty-bitmap: Add bdrv_dirty_iter_next_area
Date: Mon, 2 Oct 2017 16:32:00 +0300
User-agent: Mozilla/5.0 (X11; Linux x86_64; rv:52.0) Gecko/20100101 Thunderbird/52.3.0

25.09.2017 18:49, Vladimir Sementsov-Ogievskiy wrote:
I have a patch on list, which adds hbitmap_next_zero function, it may help
https://lists.nongnu.org/archive/html/qemu-devel/2017-02/msg00809.html

there is a mistake in this hbitmap_next_zero, I'll send today corrected version as part of small backup-related series.



13.09.2017 21:19, Max Reitz wrote:
This new function allows to look for a consecutively dirty area in a
dirty bitmap.

Signed-off-by: Max Reitz <address@hidden>
---
  include/block/dirty-bitmap.h |  2 ++
  block/dirty-bitmap.c         | 52 ++++++++++++++++++++++++++++++++++++++++++++
  2 files changed, 54 insertions(+)

diff --git a/include/block/dirty-bitmap.h b/include/block/dirty-bitmap.h
index a79a58d2c3..7654748700 100644
--- a/include/block/dirty-bitmap.h
+++ b/include/block/dirty-bitmap.h
@@ -90,6 +90,8 @@ void bdrv_set_dirty_bitmap_locked(BdrvDirtyBitmap *bitmap,
  void bdrv_reset_dirty_bitmap_locked(BdrvDirtyBitmap *bitmap,
                                      int64_t cur_sector, int64_t nr_sectors);
  int64_t bdrv_dirty_iter_next(BdrvDirtyBitmapIter *iter);
+bool bdrv_dirty_iter_next_area(BdrvDirtyBitmapIter *iter, uint64_t max_offset,
+                               uint64_t *offset, int *bytes);
  void bdrv_set_dirty_iter(BdrvDirtyBitmapIter *hbi, int64_t sector_num);
  int64_t bdrv_get_dirty_count(BdrvDirtyBitmap *bitmap);
  int64_t bdrv_get_meta_dirty_count(BdrvDirtyBitmap *bitmap);
diff --git a/block/dirty-bitmap.c b/block/dirty-bitmap.c
index aee57cf8c8..81b2f78016 100644
--- a/block/dirty-bitmap.c
+++ b/block/dirty-bitmap.c
@@ -550,6 +550,58 @@ int64_t bdrv_dirty_iter_next(BdrvDirtyBitmapIter *iter)
      return hbitmap_iter_next(&iter->hbi, true);
  }
  +/**
+ * Return the next consecutively dirty area in the dirty bitmap
+ * belonging to the given iterator @iter.
+ *
+ * @max_offset: Maximum value that may be returned for
+ *              *offset + *bytes
+ * @offset:     Will contain the start offset of the next dirty area
+ * @bytes:      Will contain the length of the next dirty area
+ *
+ * Returns: True if a dirty area could be found before max_offset
+ *          (which means that *offset and *bytes then contain valid
+ *          values), false otherwise.
+ */
+bool bdrv_dirty_iter_next_area(BdrvDirtyBitmapIter *iter, uint64_t max_offset,
+                               uint64_t *offset, int *bytes)
+{
+    uint32_t granularity = bdrv_dirty_bitmap_granularity(iter->bitmap);
+    uint64_t gran_max_offset;
+    int sector_gran = granularity >> BDRV_SECTOR_BITS;
+    int64_t ret;
+    int size;
+
+    if (DIV_ROUND_UP(max_offset, BDRV_SECTOR_SIZE) == iter->bitmap->size) {
+        /* If max_offset points to the image end, round it up by the
+         * bitmap granularity */
+        gran_max_offset = ROUND_UP(max_offset, granularity);
+    } else {
+        gran_max_offset = max_offset;
+    }
+
+    ret = hbitmap_iter_next(&iter->hbi, false);
+    if (ret < 0 || (ret << BDRV_SECTOR_BITS) + granularity > gran_max_offset) {
+        return false;
+    }
+
+    *offset = ret << BDRV_SECTOR_BITS;
+    size = 0;
+
+    assert(granularity <= INT_MAX);
+
+    do {
+        /* Advance iterator */
+        ret = hbitmap_iter_next(&iter->hbi, true);
+        size += granularity;
+    } while ((ret << BDRV_SECTOR_BITS) + granularity <= gran_max_offset && +             hbitmap_iter_next(&iter->hbi, false) == ret + sector_gran &&
+             size <= INT_MAX - granularity);
+
+    *bytes = MIN(size, max_offset - *offset);
+    return true;
+}
+
  /* Called within bdrv_dirty_bitmap_lock..unlock */
  void bdrv_set_dirty_bitmap_locked(BdrvDirtyBitmap *bitmap,
                                    int64_t cur_sector, int64_t nr_sectors)




--
Best regards,
Vladimir


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