[Qemu-devel] [PATCHv2 04/20] block: introduce bdrv_has_discard_zeroes and bdrv_has_discard_write_zeroes

[Peter Lieven]

Signed-off-by: Peter Lieven <address@hidden>
---
 block.c                   |   29 +++++++++++++++++++++++++++++
 include/block/block.h     |    2 ++
 include/block/block_int.h |   13 +++++++++++++
 3 files changed, 44 insertions(+)

diff --git a/block.c b/block.c
index 6f498fc..177720e 100644
--- a/block.c
+++ b/block.c
@@ -3045,6 +3045,35 @@ int bdrv_has_zero_init(BlockDriverState *bs)
     return 0;
 }
 
+int bdrv_has_discard_zeroes(BlockDriverState *bs)
+{
+    assert(bs->drv);
+
+    if (bs->backing_hd) {
+        return 0;
+    }
+    if (bs->drv->bdrv_has_discard_zeroes) {
+        return bs->drv->bdrv_has_discard_zeroes(bs);
+    }
+
+    return 0;
+}
+
+int bdrv_has_discard_write_zeroes(BlockDriverState *bs)
+{
+    assert(bs->drv);
+
+    if (bs->backing_hd || !(bs->open_flags & BDRV_O_UNMAP)) {
+        return 0;
+    }
+
+    if (bs->drv->bdrv_has_discard_write_zeroes) {
+        return bs->drv->bdrv_has_discard_write_zeroes(bs);
+    }
+
+    return 0;
+}
+
 typedef struct BdrvCoGetBlockStatusData {
     BlockDriverState *bs;
     BlockDriverState *base;
diff --git a/include/block/block.h b/include/block/block.h
index 0328234..8aa325a 100644
--- a/include/block/block.h
+++ b/include/block/block.h
@@ -307,6 +307,8 @@ int bdrv_discard(BlockDriverState *bs, int64_t sector_num, 
int nb_sectors);
 int bdrv_co_discard(BlockDriverState *bs, int64_t sector_num, int nb_sectors);
 int bdrv_has_zero_init_1(BlockDriverState *bs);
 int bdrv_has_zero_init(BlockDriverState *bs);
+int bdrv_has_discard_zeroes(BlockDriverState *bs);
+int bdrv_has_discard_write_zeroes(BlockDriverState *bs);
 int64_t bdrv_get_block_status(BlockDriverState *bs, int64_t sector_num,
                               int nb_sectors, int *pnum);
 int bdrv_is_allocated(BlockDriverState *bs, int64_t sector_num, int nb_sectors,
diff --git a/include/block/block_int.h b/include/block/block_int.h
index 26bad36..85c3474 100644
--- a/include/block/block_int.h
+++ b/include/block/block_int.h
@@ -202,6 +202,19 @@ struct BlockDriver {
      */
     int (*bdrv_has_zero_init)(BlockDriverState *bs);
 
+    /*
+     * Returns 1 if discarded blocks read back as zeroes, 0 otherwise.
+     */
+    int (*bdrv_has_discard_zeroes)(BlockDriverState *bs);
+
+    /*
+     * Returns 1 if the driver can optimize writing zeroes by discarding
+     * sectors. It is additionally required that the block device is
+     * opened with BDRV_O_UNMAP and the that write zeroes request carries
+     * the BDRV_REQ_MAY_UNMAP flag for this to work.
+     */
+    int (*bdrv_has_discard_write_zeroes)(BlockDriverState *bs);
+
     QLIST_ENTRY(BlockDriver) list;
 };
 
-- 
1.7.9.5