[Qemu-devel] [RFC PATCH 06/17] block: use bdrv_{co, aio}_discard for write_zeroes operations

[Paolo Bonzini <pbonzini@redhat.com>]

Remove the bdrv_co_write_zeroes callback.  Instead use the discard
information from bdrv_get_info to choose between bdrv_co_discard
and a normal write.

Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
---
 block.c     |   12 +++++++++---
 block/qed.c |    8 --------
 block_int.h |    8 --------
 3 files changed, 9 insertions(+), 19 deletions(-)

diff --git a/block.c b/block.c
index e4f7782..34db914 100644
--- a/block.c
+++ b/block.c
@@ -1656,6 +1656,7 @@ static int coroutine_fn bdrv_co_do_copy_on_readv(BlockDriverState *bs,
     int cluster_nb_sectors;
     size_t skip_bytes;
     int ret;
+    BlockDriverInfo bdi;
 
     /* Cover entire cluster so no additional backing file I/O is required when
      * allocating cluster in the image file.
@@ -1676,7 +1677,8 @@ static int coroutine_fn bdrv_co_do_copy_on_readv(BlockDriverState *bs,
         goto err;
     }
 
-    if (drv->bdrv_co_write_zeroes &&
+    /* If it is worthless, do not check if the buffer is zero.  */
+    if (bdrv_get_info(bs, &bdi) >= 0 && bdi.discard_zeroes_data &&
         buffer_is_zero(bounce_buffer, iov.iov_len)) {
         ret = bdrv_co_do_write_zeroes(bs, cluster_sector_num,
                                       cluster_nb_sectors, &bounce_qiov);
@@ -1785,13 +1787,17 @@ static int coroutine_fn bdrv_co_do_write_zeroes(BlockDriverState *bs,
     int64_t sector_num, int nb_sectors, QEMUIOVector *qiov)
 {
     BlockDriver *drv = bs->drv;
+    BlockDriverInfo bdi;
     QEMUIOVector my_qiov;
     struct iovec iov;
     int ret;
 
     /* First try the efficient write zeroes operation */
-    if (drv->bdrv_co_write_zeroes) {
-        return drv->bdrv_co_write_zeroes(bs, sector_num, nb_sectors);
+    if (bdrv_get_info(bs, &bdi) >= 0 && bdi.discard_zeroes_data &&
+        bdi.discard_granularity &&
+        (sector_num & (bdi.discard_granularity - 1)) == 0 &&
+        (nb_sectors & (bdi.discard_granularity - 1)) == 0) {
+        return bdrv_co_discard(bs, sector_num, nb_sectors);
     }
 
     if (qiov) {
diff --git a/block/qed.c b/block/qed.c
index 9944be5..33fe03f 100644
--- a/block/qed.c
+++ b/block/qed.c
@@ -1395,13 +1395,6 @@ static BlockDriverAIOCB *bdrv_qed_aio_flush(BlockDriverState *bs,
     return bdrv_aio_flush(bs->file, cb, opaque);
 }
 
-static int coroutine_fn bdrv_qed_co_write_zeroes(BlockDriverState *bs,
-                                                 int64_t sector_num,
-                                                 int nb_sectors)
-{
-    return bdrv_co_discard(bs, sector_num, nb_sectors);
-}
-
 static int bdrv_qed_truncate(BlockDriverState *bs, int64_t offset)
 {
     BDRVQEDState *s = bs->opaque;
@@ -1563,7 +1556,6 @@ static BlockDriver bdrv_qed = {
     .bdrv_aio_writev          = bdrv_qed_aio_writev,
     .bdrv_aio_flush           = bdrv_qed_aio_flush,
     .bdrv_aio_discard         = bdrv_qed_aio_discard,
-    .bdrv_co_write_zeroes     = bdrv_qed_co_write_zeroes,
     .bdrv_truncate            = bdrv_qed_truncate,
     .bdrv_getlength           = bdrv_qed_getlength,
     .bdrv_get_info            = bdrv_qed_get_info,
diff --git a/block_int.h b/block_int.h
index b460c36..2e8cdfe 100644
--- a/block_int.h
+++ b/block_int.h
@@ -131,14 +131,6 @@ struct BlockDriver {
         int64_t sector_num, int nb_sectors, QEMUIOVector *qiov);
     int coroutine_fn (*bdrv_co_writev)(BlockDriverState *bs,
         int64_t sector_num, int nb_sectors, QEMUIOVector *qiov);
-    /*
-     * Efficiently zero a region of the disk image.  Typically an image format
-     * would use a compact metadata representation to implement this.  This
-     * function pointer may be NULL and .bdrv_co_writev() will be called
-     * instead.
-     */
-    int coroutine_fn (*bdrv_co_write_zeroes)(BlockDriverState *bs,
-        int64_t sector_num, int nb_sectors);
     int coroutine_fn (*bdrv_co_discard)(BlockDriverState *bs,
         int64_t sector_num, int nb_sectors);
     int coroutine_fn (*bdrv_co_is_allocated)(BlockDriverState *bs,
-- 
1.7.7.6