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[PATCH 8/8] block: drop unallocated_blocks_are_zero
From: |
Vladimir Sementsov-Ogievskiy |
Subject: |
[PATCH 8/8] block: drop unallocated_blocks_are_zero |
Date: |
Wed, 6 May 2020 12:25:13 +0300 |
Currently this field only set by qed and qcow2. But in fact, all
backing-supporting formats (parallels, qcow, qcow2, qed, vmdk) share
this semantics: on unallocated blocks, if there is no backing file they
just memset the buffer with zeroes.
So, document this behavior for .supports_backing and drop
.unallocated_blocks_are_zero
Signed-off-by: Vladimir Sementsov-Ogievskiy <address@hidden>
---
include/block/block.h | 6 ------
include/block/block_int.h | 13 ++++++++++++-
block.c | 15 ---------------
block/io.c | 8 ++++----
block/qcow2.c | 1 -
block/qed.c | 1 -
6 files changed, 16 insertions(+), 28 deletions(-)
diff --git a/include/block/block.h b/include/block/block.h
index 8b62429aa4..db1cb503ec 100644
--- a/include/block/block.h
+++ b/include/block/block.h
@@ -21,11 +21,6 @@ typedef struct BlockDriverInfo {
/* offset at which the VM state can be saved (0 if not possible) */
int64_t vm_state_offset;
bool is_dirty;
- /*
- * True if unallocated blocks read back as zeroes. This is equivalent
- * to the LBPRZ flag in the SCSI logical block provisioning page.
- */
- bool unallocated_blocks_are_zero;
/*
* True if this block driver only supports compressed writes
*/
@@ -431,7 +426,6 @@ int bdrv_co_pdiscard(BdrvChild *child, int64_t offset,
int64_t bytes);
int bdrv_has_zero_init_1(BlockDriverState *bs);
int bdrv_has_zero_init(BlockDriverState *bs);
int bdrv_has_zero_init_truncate(BlockDriverState *bs);
-bool bdrv_unallocated_blocks_are_zero(BlockDriverState *bs);
bool bdrv_can_write_zeroes_with_unmap(BlockDriverState *bs);
int bdrv_block_status(BlockDriverState *bs, int64_t offset,
int64_t bytes, int64_t *pnum, int64_t *map,
diff --git a/include/block/block_int.h b/include/block/block_int.h
index 92335f33c7..c156b22c6b 100644
--- a/include/block/block_int.h
+++ b/include/block/block_int.h
@@ -115,7 +115,18 @@ struct BlockDriver {
*/
bool bdrv_needs_filename;
- /* Set if a driver can support backing files */
+ /*
+ * Set if a driver can support backing files. This also implies the
+ * following semantics:
+ *
+ * - Return status 0 of .bdrv_co_block_status means that corresponding
+ * blocks are not allocated in this layer of backing-chain
+ * - For such (unallocated) blocks, read will:
+ * - read from backing file if there is one and big enough
+ * - fill buffer with zeroes if there is no backing file
+ * - space after EOF of the backing file considered as zero
+ * (corresponding part of read-buffer must be zeroed by driver)
+ */
bool supports_backing;
/* For handling image reopen for split or non-split files */
diff --git a/block.c b/block.c
index cf5c19b1db..0283fdecbc 100644
--- a/block.c
+++ b/block.c
@@ -5305,21 +5305,6 @@ int bdrv_has_zero_init_truncate(BlockDriverState *bs)
return 0;
}
-bool bdrv_unallocated_blocks_are_zero(BlockDriverState *bs)
-{
- BlockDriverInfo bdi;
-
- if (bs->backing) {
- return false;
- }
-
- if (bdrv_get_info(bs, &bdi) == 0) {
- return bdi.unallocated_blocks_are_zero;
- }
-
- return false;
-}
-
bool bdrv_can_write_zeroes_with_unmap(BlockDriverState *bs)
{
if (!(bs->open_flags & BDRV_O_UNMAP)) {
diff --git a/block/io.c b/block/io.c
index a4f9714230..484adec5a1 100644
--- a/block/io.c
+++ b/block/io.c
@@ -2385,16 +2385,16 @@ static int coroutine_fn
bdrv_co_block_status(BlockDriverState *bs,
if (ret & (BDRV_BLOCK_DATA | BDRV_BLOCK_ZERO)) {
ret |= BDRV_BLOCK_ALLOCATED;
- } else if (want_zero) {
- if (bdrv_unallocated_blocks_are_zero(bs)) {
- ret |= BDRV_BLOCK_ZERO;
- } else if (bs->backing) {
+ } else if (want_zero && bs->drv->supports_backing) {
+ if (bs->backing) {
BlockDriverState *bs2 = bs->backing->bs;
int64_t size2 = bdrv_getlength(bs2);
if (size2 >= 0 && offset >= size2) {
ret |= BDRV_BLOCK_ZERO;
}
+ } else {
+ ret |= BDRV_BLOCK_ZERO;
}
}
diff --git a/block/qcow2.c b/block/qcow2.c
index 2ba0b17c39..dc3c0aac2b 100644
--- a/block/qcow2.c
+++ b/block/qcow2.c
@@ -4858,7 +4858,6 @@ err:
static int qcow2_get_info(BlockDriverState *bs, BlockDriverInfo *bdi)
{
BDRVQcow2State *s = bs->opaque;
- bdi->unallocated_blocks_are_zero = true;
bdi->cluster_size = s->cluster_size;
bdi->vm_state_offset = qcow2_vm_state_offset(s);
return 0;
diff --git a/block/qed.c b/block/qed.c
index b0fdb8f565..fb7833dc8b 100644
--- a/block/qed.c
+++ b/block/qed.c
@@ -1514,7 +1514,6 @@ static int bdrv_qed_get_info(BlockDriverState *bs,
BlockDriverInfo *bdi)
memset(bdi, 0, sizeof(*bdi));
bdi->cluster_size = s->header.cluster_size;
bdi->is_dirty = s->header.features & QED_F_NEED_CHECK;
- bdi->unallocated_blocks_are_zero = true;
return 0;
}
--
2.21.0
- Re: [PATCH 3/8] block/crypto: drop unallocated_blocks_are_zero, (continued)
- [PATCH 4/8] block/iscsi: drop unallocated_blocks_are_zero, Vladimir Sementsov-Ogievskiy, 2020/05/06
- [PATCH 5/8] block/file-posix: drop unallocated_blocks_are_zero, Vladimir Sementsov-Ogievskiy, 2020/05/06
- [PATCH 6/8] block/vhdx: drop unallocated_blocks_are_zero, Vladimir Sementsov-Ogievskiy, 2020/05/06
- [PATCH 7/8] qemu-img: convert: don't use unallocated_blocks_are_zero, Vladimir Sementsov-Ogievskiy, 2020/05/06
- [PATCH 8/8] block: drop unallocated_blocks_are_zero,
Vladimir Sementsov-Ogievskiy <=
- Re: [PATCH 8/8] block: drop unallocated_blocks_are_zero, Eric Blake, 2020/05/06