Since gluster already copies file-posix for lseek usage in block
status, it also makes sense to copy it for learning if the image
currently reads as all zeroes.
Signed-off-by: Eric Blake <ebl...@redhat.com>
---
block/gluster.c | 20 ++++++++++++++++++++
1 file changed, 20 insertions(+)
diff --git a/block/gluster.c b/block/gluster.c
index 9d952c70981b..0417a86547c8 100644
--- a/block/gluster.c
+++ b/block/gluster.c
@@ -1464,6 +1464,22 @@ exit:
return -ENOTSUP;
}
+static int qemu_gluster_known_zeroes(BlockDriverState *bs)
+{
+ /*
+ * GlusterFS volume could be backed by a block device, with no way
+ * to query if regions added by creation or truncation will read
+ * as zeroes. However, we can use lseek(SEEK_DATA) to check if
+ * contents currently read as zero.
+ */
+ off_t data, hole;
+
+ if (find_allocation(bs, 0, &data, &hole) == -ENXIO) {
+ return BDRV_ZERO_OPEN;
+ }
+ return 0;
+}
+
/*
* Returns the allocation status of the specified offset.
*
@@ -1561,6 +1577,7 @@ static BlockDriver bdrv_gluster = {
.bdrv_co_readv = qemu_gluster_co_readv,
.bdrv_co_writev = qemu_gluster_co_writev,
.bdrv_co_flush_to_disk = qemu_gluster_co_flush_to_disk,
+ .bdrv_known_zeroes = qemu_gluster_known_zeroes,
#ifdef CONFIG_GLUSTERFS_DISCARD
.bdrv_co_pdiscard = qemu_gluster_co_pdiscard,
#endif
@@ -1591,6 +1608,7 @@ static BlockDriver bdrv_gluster_tcp = {
.bdrv_co_readv = qemu_gluster_co_readv,
.bdrv_co_writev = qemu_gluster_co_writev,
.bdrv_co_flush_to_disk = qemu_gluster_co_flush_to_disk,
+ .bdrv_known_zeroes = qemu_gluster_known_zeroes,
#ifdef CONFIG_GLUSTERFS_DISCARD
.bdrv_co_pdiscard = qemu_gluster_co_pdiscard,
#endif
@@ -1621,6 +1639,7 @@ static BlockDriver bdrv_gluster_unix = {
.bdrv_co_readv = qemu_gluster_co_readv,
.bdrv_co_writev = qemu_gluster_co_writev,
.bdrv_co_flush_to_disk = qemu_gluster_co_flush_to_disk,
+ .bdrv_known_zeroes = qemu_gluster_known_zeroes,
#ifdef CONFIG_GLUSTERFS_DISCARD
.bdrv_co_pdiscard = qemu_gluster_co_pdiscard,
#endif
@@ -1657,6 +1676,7 @@ static BlockDriver bdrv_gluster_rdma = {
.bdrv_co_readv = qemu_gluster_co_readv,
.bdrv_co_writev = qemu_gluster_co_writev,
.bdrv_co_flush_to_disk = qemu_gluster_co_flush_to_disk,
+ .bdrv_known_zeroes = qemu_gluster_known_zeroes,
#ifdef CONFIG_GLUSTERFS_DISCARD
.bdrv_co_pdiscard = qemu_gluster_co_pdiscard,
#endif
--
2.24.1
