From: Max Reitz <mreitz@redhat.com>
To: qemu-block@nongnu.org
Cc: Kevin Wolf <kwolf@redhat.com>,
Peter Maydell <peter.maydell@linaro.org>,
qemu-devel@nongnu.org, Max Reitz <mreitz@redhat.com>
Subject: [Qemu-devel] [PULL 04/17] block: Add bdrv_has_zero_init_truncate()
Date: Mon, 19 Aug 2019 18:17:10 +0200 [thread overview]
Message-ID: <20190819161723.7746-5-mreitz@redhat.com> (raw)
In-Reply-To: <20190819161723.7746-1-mreitz@redhat.com>
No .bdrv_has_zero_init() implementation returns 1 if growing the file
would add non-zero areas (at least with PREALLOC_MODE_OFF), so using it
in lieu of this new function was always safe.
But on the other hand, it is possible that growing an image that is not
zero-initialized would still add a zero-initialized area, like when
using nonpreallocating truncation on a preallocated image. For callers
that care only about truncation, not about creation with potential
preallocation, this new function is useful.
Alternatively, we could have added a PreallocMode parameter to
bdrv_has_zero_init(). But the only user would have been qemu-img
convert, which does not have a plain PreallocMode value right now -- it
would have to parse the creation option to obtain it. Therefore, the
simpler solution is to let bdrv_has_zero_init() inquire the
preallocation status and add the new bdrv_has_zero_init_truncate() that
presupposes PREALLOC_MODE_OFF.
Signed-off-by: Max Reitz <mreitz@redhat.com>
Message-id: 20190724171239.8764-4-mreitz@redhat.com
Reviewed-by: Maxim Levitsky <mlevitsk@redhat.com>
Reviewed-by: Stefano Garzarella <sgarzare@redhat.com>
Signed-off-by: Max Reitz <mreitz@redhat.com>
---
include/block/block.h | 1 +
include/block/block_int.h | 7 +++++++
block.c | 21 +++++++++++++++++++++
3 files changed, 29 insertions(+)
diff --git a/include/block/block.h b/include/block/block.h
index 89e40318cf..124ad40809 100644
--- a/include/block/block.h
+++ b/include/block/block.h
@@ -443,6 +443,7 @@ int bdrv_pdiscard(BdrvChild *child, int64_t offset, int64_t bytes);
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,
diff --git a/include/block/block_int.h b/include/block/block_int.h
index 8fa011654a..ceec8c2f56 100644
--- a/include/block/block_int.h
+++ b/include/block/block_int.h
@@ -419,9 +419,16 @@ struct BlockDriver {
/*
* Returns 1 if newly created images are guaranteed to contain only
* zeros, 0 otherwise.
+ * Must return 0 if .bdrv_has_zero_init_truncate() returns 0.
*/
int (*bdrv_has_zero_init)(BlockDriverState *bs);
+ /*
+ * Returns 1 if new areas added by growing the image with
+ * PREALLOC_MODE_OFF contain only zeros, 0 otherwise.
+ */
+ int (*bdrv_has_zero_init_truncate)(BlockDriverState *bs);
+
/* Remove fd handlers, timers, and other event loop callbacks so the event
* loop is no longer in use. Called with no in-flight requests and in
* depth-first traversal order with parents before child nodes.
diff --git a/block.c b/block.c
index 3e698e9cab..874a29a983 100644
--- a/block.c
+++ b/block.c
@@ -5078,6 +5078,27 @@ int bdrv_has_zero_init(BlockDriverState *bs)
return 0;
}
+int bdrv_has_zero_init_truncate(BlockDriverState *bs)
+{
+ if (!bs->drv) {
+ return 0;
+ }
+
+ if (bs->backing) {
+ /* Depends on the backing image length, but better safe than sorry */
+ return 0;
+ }
+ if (bs->drv->bdrv_has_zero_init_truncate) {
+ return bs->drv->bdrv_has_zero_init_truncate(bs);
+ }
+ if (bs->file && bs->drv->is_filter) {
+ return bdrv_has_zero_init_truncate(bs->file->bs);
+ }
+
+ /* safe default */
+ return 0;
+}
+
bool bdrv_unallocated_blocks_are_zero(BlockDriverState *bs)
{
BlockDriverInfo bdi;
--
2.21.0
next prev parent reply other threads:[~2019-08-19 16:23 UTC|newest]
Thread overview: 19+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-08-19 16:17 [Qemu-devel] [PULL 00/17] Block patches Max Reitz
2019-08-19 16:17 ` [Qemu-devel] [PULL 01/17] LUKS: support preallocation Max Reitz
2019-08-19 16:17 ` [Qemu-devel] [PULL 02/17] qemu-img: Fix bdrv_has_zero_init() use in convert Max Reitz
2019-08-19 16:17 ` [Qemu-devel] [PULL 03/17] mirror: Fix bdrv_has_zero_init() use Max Reitz
2019-08-19 16:17 ` Max Reitz [this message]
2019-08-19 16:17 ` [Qemu-devel] [PULL 05/17] block: Implement .bdrv_has_zero_init_truncate() Max Reitz
2019-08-19 16:17 ` [Qemu-devel] [PULL 06/17] block: Use bdrv_has_zero_init_truncate() Max Reitz
2019-08-19 16:17 ` [Qemu-devel] [PULL 07/17] qcow2: Fix .bdrv_has_zero_init() Max Reitz
2019-08-19 16:17 ` [Qemu-devel] [PULL 08/17] vdi: " Max Reitz
2019-08-19 16:17 ` [Qemu-devel] [PULL 09/17] vhdx: " Max Reitz
2019-08-19 16:17 ` [Qemu-devel] [PULL 10/17] iotests: Convert to preallocated encrypted qcow2 Max Reitz
2019-08-19 16:17 ` [Qemu-devel] [PULL 11/17] iotests: Test convert -n to pre-filled image Max Reitz
2019-08-19 16:17 ` [Qemu-devel] [PULL 12/17] iotests: Full mirror to existing non-zero image Max Reitz
2019-08-19 16:17 ` [Qemu-devel] [PULL 13/17] vdi: Make block_status recurse for fixed images Max Reitz
2019-08-19 16:17 ` [Qemu-devel] [PULL 14/17] vmdk: Make block_status recurse for flat extents Max Reitz
2019-08-19 16:17 ` [Qemu-devel] [PULL 15/17] vpc: Do not return RAW from block_status Max Reitz
2019-08-19 16:17 ` [Qemu-devel] [PULL 16/17] iotests: Fix 141 when run with qed Max Reitz
2019-08-19 16:17 ` [Qemu-devel] [PULL 17/17] doc: Preallocation does not require writing zeroes Max Reitz
2019-08-20 12:40 ` [Qemu-devel] [PULL 00/17] Block patches Peter Maydell
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