The flag is supposed to indicate that the region of the disk image has
to be sufficiently allocated so it reads as zeroes.
The call with the flag set must return -ENOTSUP if allocation cannot
be done efficiently.
This has to be made sure of by both
- the drivers that support the flag
- and the common block layer (so it will not fall back to any slowpath
(like writing zero buffers) in case the driver does not support
the flag).
Signed-off-by: Anton Nefedov <anton.nefedov@virtuozzo.com>
Reviewed-by: Alberto Garcia <berto@igalia.com>
---
include/block/block.h | 9 ++++++++-
include/block/block_int.h | 2 +-
block/io.c | 18 ++++++++++++++++--
3 files changed, 25 insertions(+), 4 deletions(-)
diff --git a/include/block/block.h b/include/block/block.h
index 7f5453b45b..f571082415 100644
--- a/include/block/block.h
+++ b/include/block/block.h
@@ -83,8 +83,15 @@ typedef enum {
*/
BDRV_REQ_SERIALISING = 0x80,
+ /* The BDRV_REQ_ALLOCATE flag is used to indicate that the driver has to
+ * efficiently allocate the space so it reads as zeroes, or return an error.
+ * If this flag is set then BDRV_REQ_ZERO_WRITE must also be set.
+ * This flag cannot be set together with BDRV_REQ_MAY_UNMAP.
+ */
+ BDRV_REQ_ALLOCATE = 0x100,
+
/* Mask of valid flags */
- BDRV_REQ_MASK = 0xff,
+ BDRV_REQ_MASK = 0x1ff,
} BdrvRequestFlags;
typedef struct BlockSizes {
diff --git a/include/block/block_int.h b/include/block/block_int.h
index f605622216..ff84c5d8aa 100644
--- a/include/block/block_int.h
+++ b/include/block/block_int.h
@@ -724,7 +724,7 @@ struct BlockDriverState {
* their children. */
unsigned int supported_write_flags;
/* Flags honored during pwrite_zeroes (so far: BDRV_REQ_FUA,
- * BDRV_REQ_MAY_UNMAP, BDRV_REQ_WRITE_UNCHANGED) */
+ * BDRV_REQ_MAY_UNMAP, BDRV_REQ_WRITE_UNCHANGED, BDRV_REQ_ALLOCATE) */
unsigned int supported_zero_flags;
/* the following member gives a name to every node on the bs graph. */
diff --git a/block/io.c b/block/io.c
index bd9d688f8b..d9d7644858 100644
--- a/block/io.c
+++ b/block/io.c
@@ -1534,7 +1534,7 @@ static int coroutine_fn bdrv_co_do_pwrite_zeroes(BlockDriverState *bs,
assert(!bs->supported_zero_flags);
}
- if (ret == -ENOTSUP) {
+ if (ret == -ENOTSUP && !(flags & BDRV_REQ_ALLOCATE)) {
/* Fall back to bounce buffer if write zeroes is unsupported */
BdrvRequestFlags write_flags = flags & ~BDRV_REQ_ZERO_WRITE;
@@ -1702,7 +1702,9 @@ static int coroutine_fn bdrv_aligned_pwritev(BdrvChild *child,
!(flags & BDRV_REQ_ZERO_WRITE) && drv->bdrv_co_pwrite_zeroes &&
qemu_iovec_is_zero(qiov)) {
flags |= BDRV_REQ_ZERO_WRITE;
- if (bs->detect_zeroes == BLOCKDEV_DETECT_ZEROES_OPTIONS_UNMAP) {
+ if (bs->detect_zeroes == BLOCKDEV_DETECT_ZEROES_OPTIONS_UNMAP &&
+ !(flags & BDRV_REQ_ALLOCATE))
+ {
flags |= BDRV_REQ_MAY_UNMAP;
}
}
@@ -1773,6 +1775,9 @@ static int coroutine_fn bdrv_co_do_zero_pwritev(BdrvChild *child,
assert(flags & BDRV_REQ_ZERO_WRITE);
if (head_padding_bytes || tail_padding_bytes) {
+ if (flags & BDRV_REQ_ALLOCATE) {
+ return -ENOTSUP;
+ }
buf = qemu_blockalign(bs, align);
iov = (struct iovec) {
.iov_base = buf,
@@ -1858,6 +1863,9 @@ int coroutine_fn bdrv_co_pwritev(BdrvChild *child,
bool use_local_qiov = false;
int ret;
+ assert(!((flags & BDRV_REQ_ALLOCATE) && (flags & BDRV_REQ_MAY_UNMAP)));
+ assert(!((flags & BDRV_REQ_ALLOCATE) && !(flags & BDRV_REQ_ZERO_WRITE)));
+
trace_bdrv_co_pwritev(child->bs, offset, bytes, flags);
if (!bs->drv) {
@@ -1980,6 +1988,12 @@ int coroutine_fn bdrv_co_pwrite_zeroes(BdrvChild *child, int64_t offset,
{
trace_bdrv_co_pwrite_zeroes(child->bs, offset, bytes, flags);
+ if ((flags & BDRV_REQ_ALLOCATE) &&
+ !(child->bs->supported_zero_flags & BDRV_REQ_ALLOCATE))
+ {
+ return -ENOTSUP;
+ }
+
if (!(child->bs->open_flags & BDRV_O_UNMAP)) {
flags &= ~BDRV_REQ_MAY_UNMAP;
}
--
2.17.1
03.12.2018 13:14, Anton Nefedov wrote:
> The flag is supposed to indicate that the region of the disk image has
> to be sufficiently allocated so it reads as zeroes.
>
> The call with the flag set must return -ENOTSUP if allocation cannot
> be done efficiently.
> This has to be made sure of by both
> - the drivers that support the flag
> - and the common block layer (so it will not fall back to any slowpath
> (like writing zero buffers) in case the driver does not support
> the flag).
>
> Signed-off-by: Anton Nefedov <anton.nefedov@virtuozzo.com>
> Reviewed-by: Alberto Garcia <berto@igalia.com>
> ---
> include/block/block.h | 9 ++++++++-
> include/block/block_int.h | 2 +-
> block/io.c | 18 ++++++++++++++++--
> 3 files changed, 25 insertions(+), 4 deletions(-)
>
> diff --git a/include/block/block.h b/include/block/block.h
> index 7f5453b45b..f571082415 100644
> --- a/include/block/block.h
> +++ b/include/block/block.h
> @@ -83,8 +83,15 @@ typedef enum {
> */
> BDRV_REQ_SERIALISING = 0x80,
>
> + /* The BDRV_REQ_ALLOCATE flag is used to indicate that the driver has to
> + * efficiently allocate the space so it reads as zeroes, or return an error.
> + * If this flag is set then BDRV_REQ_ZERO_WRITE must also be set.
> + * This flag cannot be set together with BDRV_REQ_MAY_UNMAP.
and, may be, it can't be set with FUA too?
> + */
> + BDRV_REQ_ALLOCATE = 0x100,
> +
> /* Mask of valid flags */
> - BDRV_REQ_MASK = 0xff,
> + BDRV_REQ_MASK = 0x1ff,
> } BdrvRequestFlags;
>
> typedef struct BlockSizes {
> diff --git a/include/block/block_int.h b/include/block/block_int.h
> index f605622216..ff84c5d8aa 100644
> --- a/include/block/block_int.h
> +++ b/include/block/block_int.h
> @@ -724,7 +724,7 @@ struct BlockDriverState {
> * their children. */
> unsigned int supported_write_flags;
> /* Flags honored during pwrite_zeroes (so far: BDRV_REQ_FUA,
> - * BDRV_REQ_MAY_UNMAP, BDRV_REQ_WRITE_UNCHANGED) */
> + * BDRV_REQ_MAY_UNMAP, BDRV_REQ_WRITE_UNCHANGED, BDRV_REQ_ALLOCATE) */
> unsigned int supported_zero_flags;
>
> /* the following member gives a name to every node on the bs graph. */
> diff --git a/block/io.c b/block/io.c
> index bd9d688f8b..d9d7644858 100644
> --- a/block/io.c
> +++ b/block/io.c
> @@ -1534,7 +1534,7 @@ static int coroutine_fn bdrv_co_do_pwrite_zeroes(BlockDriverState *bs,
> assert(!bs->supported_zero_flags);
> }
>
> - if (ret == -ENOTSUP) {
> + if (ret == -ENOTSUP && !(flags & BDRV_REQ_ALLOCATE)) {
> /* Fall back to bounce buffer if write zeroes is unsupported */
> BdrvRequestFlags write_flags = flags & ~BDRV_REQ_ZERO_WRITE;
>
> @@ -1702,7 +1702,9 @@ static int coroutine_fn bdrv_aligned_pwritev(BdrvChild *child,
> !(flags & BDRV_REQ_ZERO_WRITE) && drv->bdrv_co_pwrite_zeroes &&
> qemu_iovec_is_zero(qiov)) {
> flags |= BDRV_REQ_ZERO_WRITE;
> - if (bs->detect_zeroes == BLOCKDEV_DETECT_ZEROES_OPTIONS_UNMAP) {
> + if (bs->detect_zeroes == BLOCKDEV_DETECT_ZEROES_OPTIONS_UNMAP &&
> + !(flags & BDRV_REQ_ALLOCATE))
dead check. we are in if (!(flags & BDRV_REQ_ZERO_WRITE)), so (flags & BDRV_REQ_ALLOCATE) must be zero as well.
> + {
> flags |= BDRV_REQ_MAY_UNMAP;
> }
> }
> @@ -1773,6 +1775,9 @@ static int coroutine_fn bdrv_co_do_zero_pwritev(BdrvChild *child,
>
> assert(flags & BDRV_REQ_ZERO_WRITE);
> if (head_padding_bytes || tail_padding_bytes) {
> + if (flags & BDRV_REQ_ALLOCATE) {
> + return -ENOTSUP;
> + }
> buf = qemu_blockalign(bs, align);
> iov = (struct iovec) {
> .iov_base = buf,
> @@ -1858,6 +1863,9 @@ int coroutine_fn bdrv_co_pwritev(BdrvChild *child,
> bool use_local_qiov = false;
> int ret;
>
> + assert(!((flags & BDRV_REQ_ALLOCATE) && (flags & BDRV_REQ_MAY_UNMAP)));
> + assert(!((flags & BDRV_REQ_ALLOCATE) && !(flags & BDRV_REQ_ZERO_WRITE)));
what about FUA?
> +
> trace_bdrv_co_pwritev(child->bs, offset, bytes, flags);
>
> if (!bs->drv) {
> @@ -1980,6 +1988,12 @@ int coroutine_fn bdrv_co_pwrite_zeroes(BdrvChild *child, int64_t offset,
> {
> trace_bdrv_co_pwrite_zeroes(child->bs, offset, bytes, flags);
>
> + if ((flags & BDRV_REQ_ALLOCATE) &&
> + !(child->bs->supported_zero_flags & BDRV_REQ_ALLOCATE))
> + {
> + return -ENOTSUP;
> + }
> +
> if (!(child->bs->open_flags & BDRV_O_UNMAP)) {
> flags &= ~BDRV_REQ_MAY_UNMAP;
> }
>
--
Best regards,
Vladimir
On 5/12/2018 3:59 PM, Vladimir Sementsov-Ogievskiy wrote:
> 03.12.2018 13:14, Anton Nefedov wrote:
>> The flag is supposed to indicate that the region of the disk image has
>> to be sufficiently allocated so it reads as zeroes.
>>
>> The call with the flag set must return -ENOTSUP if allocation cannot
>> be done efficiently.
>> This has to be made sure of by both
>> - the drivers that support the flag
>> - and the common block layer (so it will not fall back to any slowpath
>> (like writing zero buffers) in case the driver does not support
>> the flag).
>>
>> Signed-off-by: Anton Nefedov <anton.nefedov@virtuozzo.com>
>> Reviewed-by: Alberto Garcia <berto@igalia.com>
>> ---
>> include/block/block.h | 9 ++++++++-
>> include/block/block_int.h | 2 +-
>> block/io.c | 18 ++++++++++++++++--
>> 3 files changed, 25 insertions(+), 4 deletions(-)
>>
>> diff --git a/include/block/block.h b/include/block/block.h
>> index 7f5453b45b..f571082415 100644
>> --- a/include/block/block.h
>> +++ b/include/block/block.h
>> @@ -83,8 +83,15 @@ typedef enum {
>> */
>> BDRV_REQ_SERIALISING = 0x80,
>>
>> + /* The BDRV_REQ_ALLOCATE flag is used to indicate that the driver has to
>> + * efficiently allocate the space so it reads as zeroes, or return an error.
>> + * If this flag is set then BDRV_REQ_ZERO_WRITE must also be set.
>> + * This flag cannot be set together with BDRV_REQ_MAY_UNMAP.
>
> and, may be, it can't be set with FUA too?
>
I don't quite see why it cannot. Even the efficient allocate call
usually implies some Unit Access, it's up to the protocol driver to
decide which exactly.
>> + */
>> + BDRV_REQ_ALLOCATE = 0x100,
>> +
>> /* Mask of valid flags */
>> - BDRV_REQ_MASK = 0xff,
>> + BDRV_REQ_MASK = 0x1ff,
>> } BdrvRequestFlags;
>>
>> typedef struct BlockSizes {
>> diff --git a/include/block/block_int.h b/include/block/block_int.h
>> index f605622216..ff84c5d8aa 100644
>> --- a/include/block/block_int.h
>> +++ b/include/block/block_int.h
>> @@ -724,7 +724,7 @@ struct BlockDriverState {
>> * their children. */
>> unsigned int supported_write_flags;
>> /* Flags honored during pwrite_zeroes (so far: BDRV_REQ_FUA,
>> - * BDRV_REQ_MAY_UNMAP, BDRV_REQ_WRITE_UNCHANGED) */
>> + * BDRV_REQ_MAY_UNMAP, BDRV_REQ_WRITE_UNCHANGED, BDRV_REQ_ALLOCATE) */
>> unsigned int supported_zero_flags;
>>
>> /* the following member gives a name to every node on the bs graph. */
>> diff --git a/block/io.c b/block/io.c
>> index bd9d688f8b..d9d7644858 100644
>> --- a/block/io.c
>> +++ b/block/io.c
>> @@ -1534,7 +1534,7 @@ static int coroutine_fn bdrv_co_do_pwrite_zeroes(BlockDriverState *bs,
>> assert(!bs->supported_zero_flags);
>> }
>>
>> - if (ret == -ENOTSUP) {
>> + if (ret == -ENOTSUP && !(flags & BDRV_REQ_ALLOCATE)) {
>> /* Fall back to bounce buffer if write zeroes is unsupported */
>> BdrvRequestFlags write_flags = flags & ~BDRV_REQ_ZERO_WRITE;
>>
>> @@ -1702,7 +1702,9 @@ static int coroutine_fn bdrv_aligned_pwritev(BdrvChild *child,
>> !(flags & BDRV_REQ_ZERO_WRITE) && drv->bdrv_co_pwrite_zeroes &&
>> qemu_iovec_is_zero(qiov)) {
>> flags |= BDRV_REQ_ZERO_WRITE;
>> - if (bs->detect_zeroes == BLOCKDEV_DETECT_ZEROES_OPTIONS_UNMAP) {
>> + if (bs->detect_zeroes == BLOCKDEV_DETECT_ZEROES_OPTIONS_UNMAP &&
>> + !(flags & BDRV_REQ_ALLOCATE))
>
>
> dead check. we are in if (!(flags & BDRV_REQ_ZERO_WRITE)), so (flags & BDRV_REQ_ALLOCATE) must be zero as well.
>
Agree.
>> + {
>> flags |= BDRV_REQ_MAY_UNMAP;
>> }
>> }
>> @@ -1773,6 +1775,9 @@ static int coroutine_fn bdrv_co_do_zero_pwritev(BdrvChild *child,
>>
>> assert(flags & BDRV_REQ_ZERO_WRITE);
>> if (head_padding_bytes || tail_padding_bytes) {
>> + if (flags & BDRV_REQ_ALLOCATE) {
>> + return -ENOTSUP;
>> + }
>> buf = qemu_blockalign(bs, align);
>> iov = (struct iovec) {
>> .iov_base = buf,
>> @@ -1858,6 +1863,9 @@ int coroutine_fn bdrv_co_pwritev(BdrvChild *child,
>> bool use_local_qiov = false;
>> int ret;
>>
>> + assert(!((flags & BDRV_REQ_ALLOCATE) && (flags & BDRV_REQ_MAY_UNMAP)));
>> + assert(!((flags & BDRV_REQ_ALLOCATE) && !(flags & BDRV_REQ_ZERO_WRITE)));
>
> what about FUA?
>
pls see above
>> +
>> trace_bdrv_co_pwritev(child->bs, offset, bytes, flags);
>>
>> if (!bs->drv) {
>> @@ -1980,6 +1988,12 @@ int coroutine_fn bdrv_co_pwrite_zeroes(BdrvChild *child, int64_t offset,
>> {
>> trace_bdrv_co_pwrite_zeroes(child->bs, offset, bytes, flags);
>>
>> + if ((flags & BDRV_REQ_ALLOCATE) &&
>> + !(child->bs->supported_zero_flags & BDRV_REQ_ALLOCATE))
>> + {
>> + return -ENOTSUP;
>> + }
>> +
>> if (!(child->bs->open_flags & BDRV_O_UNMAP)) {
>> flags &= ~BDRV_REQ_MAY_UNMAP;
>> }
>>
>
>
© 2016 - 2026 Red Hat, Inc.