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[Qemu-block] [PATCH v5 03/15] block: introduce BDRV_REQ_ALLOCATE flag
From: |
Anton Nefedov |
Subject: |
[Qemu-block] [PATCH v5 03/15] block: introduce BDRV_REQ_ALLOCATE flag |
Date: |
Wed, 1 Nov 2017 18:43:56 +0300 |
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 <address@hidden>
Reviewed-by: Eric Blake <address@hidden>
Reviewed-by: Alberto Garcia <address@hidden>
---
include/block/block.h | 6 +++++-
include/block/block_int.h | 2 +-
block/io.c | 20 +++++++++++++++++---
3 files changed, 23 insertions(+), 5 deletions(-)
diff --git a/include/block/block.h b/include/block/block.h
index fbc21da..a291db9 100644
--- a/include/block/block.h
+++ b/include/block/block.h
@@ -65,9 +65,13 @@ typedef enum {
BDRV_REQ_NO_SERIALISING = 0x8,
BDRV_REQ_FUA = 0x10,
BDRV_REQ_WRITE_COMPRESSED = 0x20,
+ /* 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.
+ */
+ BDRV_REQ_ALLOCATE = 0x40,
/* Mask of valid flags */
- BDRV_REQ_MASK = 0x3f,
+ BDRV_REQ_MASK = 0x7f,
} BdrvRequestFlags;
typedef struct BlockSizes {
diff --git a/include/block/block_int.h b/include/block/block_int.h
index a548277..3799f5f 100644
--- a/include/block/block_int.h
+++ b/include/block/block_int.h
@@ -632,7 +632,7 @@ struct BlockDriverState {
/* Flags honored during pwrite (so far: BDRV_REQ_FUA) */
unsigned int supported_write_flags;
/* Flags honored during pwrite_zeroes (so far: BDRV_REQ_FUA,
- * BDRV_REQ_MAY_UNMAP) */
+ * BDRV_REQ_MAY_UNMAP, 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 3d5ef2c..7506207 100644
--- a/block/io.c
+++ b/block/io.c
@@ -1334,7 +1334,7 @@ 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;
@@ -1420,8 +1420,8 @@ static int coroutine_fn bdrv_aligned_pwritev(BdrvChild
*child,
ret = notifier_with_return_list_notify(&bs->before_write_notifiers, req);
if (!ret && bs->detect_zeroes != BLOCKDEV_DETECT_ZEROES_OPTIONS_OFF &&
- !(flags & BDRV_REQ_ZERO_WRITE) && drv->bdrv_co_pwrite_zeroes &&
- qemu_iovec_is_zero(qiov)) {
+ !(flags & BDRV_REQ_ZERO_WRITE) && !(flags & BDRV_REQ_ALLOCATE) &&
+ drv->bdrv_co_pwrite_zeroes && qemu_iovec_is_zero(qiov)) {
flags |= BDRV_REQ_ZERO_WRITE;
if (bs->detect_zeroes == BLOCKDEV_DETECT_ZEROES_OPTIONS_UNMAP) {
flags |= BDRV_REQ_MAY_UNMAP;
@@ -1499,6 +1499,9 @@ 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,
@@ -1599,6 +1602,9 @@ int coroutine_fn bdrv_co_pwritev(BdrvChild *child,
return ret;
}
+ /* allocation request with qiov provided doesn't make much sense */
+ assert(!(qiov && (flags & BDRV_REQ_ALLOCATE)));
+
bdrv_inc_in_flight(bs);
/*
* Align write if necessary by performing a read-modify-write cycle.
@@ -1728,6 +1734,14 @@ int coroutine_fn bdrv_co_pwrite_zeroes(BdrvChild *child,
int64_t offset,
{
trace_bdrv_co_pwrite_zeroes(child->bs, offset, bytes, flags);
+ assert(!((flags & BDRV_REQ_MAY_UNMAP) && (flags & BDRV_REQ_ALLOCATE)));
+
+ 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;
}
--
2.7.4
- [Qemu-block] [PATCH v5 00/15] qcow2: space preallocation and COW improvements, Anton Nefedov, 2017/11/01
- [Qemu-block] [PATCH v5 01/15] mirror: inherit supported write/zero flags, Anton Nefedov, 2017/11/01
- [Qemu-block] [PATCH v5 02/15] blkverify: set supported write/zero flags, Anton Nefedov, 2017/11/01
- [Qemu-block] [PATCH v5 07/15] qcow2: move is_zero() up, Anton Nefedov, 2017/11/01
- [Qemu-block] [PATCH v5 04/15] block: treat BDRV_REQ_ALLOCATE as serialising, Anton Nefedov, 2017/11/01
- [Qemu-block] [PATCH v5 10/15] qcow2: set inactive flag, Anton Nefedov, 2017/11/01
- [Qemu-block] [PATCH v5 06/15] block: support BDRV_REQ_ALLOCATE in passthrough drivers, Anton Nefedov, 2017/11/01
- [Qemu-block] [PATCH v5 05/15] file-posix: support BDRV_REQ_ALLOCATE, Anton Nefedov, 2017/11/01
- [Qemu-block] [PATCH v5 08/15] qcow2: skip writing zero buffers to empty COW areas, Anton Nefedov, 2017/11/01
- [Qemu-block] [PATCH v5 03/15] block: introduce BDRV_REQ_ALLOCATE flag,
Anton Nefedov <=
- [Qemu-block] [PATCH v5 14/15] iotest 198: test BDRV_REQ_ALLOCATE, Anton Nefedov, 2017/11/01
- [Qemu-block] [PATCH v5 13/15] qcow2: do not zero out clusters if already preallocated, Anton Nefedov, 2017/11/01
- [Qemu-block] [PATCH v5 15/15] iotest 134: test cluster-misaligned encrypted write, Anton Nefedov, 2017/11/01
- [Qemu-block] [PATCH v5 09/15] qcow2: preallocation at image expand, Anton Nefedov, 2017/11/01
- [Qemu-block] [PATCH v5 11/15] qcow2: truncate preallocated space, Anton Nefedov, 2017/11/01
- [Qemu-block] [PATCH v5 12/15] qcow2: check space leak at the end of the image, Anton Nefedov, 2017/11/01