Do effective copy-on-read request when we don't need data actually. It
will be used for block-stream and NBD_CMD_CACHE.
Signed-off-by: Vladimir Sementsov-Ogievskiy <vsement...@virtuozzo.com>
---
include/block/block.h | 8 +++++++-
include/sysemu/block-backend.h | 7 +++++++
block/io.c | 18 ++++++++++++------
3 files changed, 26 insertions(+), 7 deletions(-)
diff --git a/include/block/block.h b/include/block/block.h
index f9415ed740..4662f25513 100644
--- a/include/block/block.h
+++ b/include/block/block.h
@@ -88,8 +88,14 @@ typedef enum {
* fallback. */
BDRV_REQ_NO_FALLBACK = 0x100,
+ /*
+ * BDRV_REQ_CACHE may be used only together with BDRV_REQ_COPY_ON_READ
+ * on read request and means that caller don't really need data to be
+ * written to qiov parameter which may be NULL.
+ */
+ BDRV_REQ_CACHE = 0x200,
/* Mask of valid flags */
- BDRV_REQ_MASK = 0x1ff,
+ BDRV_REQ_MASK = 0x3ff,
} BdrvRequestFlags;
typedef struct BlockSizes {
diff --git a/include/sysemu/block-backend.h b/include/sysemu/block-backend.h
index 733c4957eb..2bcecd1190 100644
--- a/include/sysemu/block-backend.h
+++ b/include/sysemu/block-backend.h
@@ -135,6 +135,13 @@ static inline int coroutine_fn blk_co_pread(BlockBackend
*blk, int64_t offset,
return blk_co_preadv(blk, offset, bytes, &qiov, flags);
}
+static inline int coroutine_fn blk_co_pcache(BlockBackend *blk, int64_t offset,
+ unsigned int bytes)
+{
+ return blk_co_preadv(blk, offset, bytes, NULL,
+ BDRV_REQ_COPY_ON_READ | BDRV_REQ_CACHE);
+}
+
static inline int coroutine_fn blk_co_pwrite(BlockBackend *blk, int64_t offset,
unsigned int bytes, void *buf,
BdrvRequestFlags flags)
diff --git a/block/io.c b/block/io.c
index 9ba1bada36..9daf7332bd 100644
--- a/block/io.c
+++ b/block/io.c
@@ -1104,7 +1104,8 @@ bdrv_driver_pwritev_compressed(BlockDriverState *bs,
uint64_t offset,
}
static int coroutine_fn bdrv_co_do_copy_on_readv(BdrvChild *child,
- int64_t offset, unsigned int bytes, QEMUIOVector *qiov)
+ int64_t offset, unsigned int bytes, QEMUIOVector *qiov,
+ int flags)
{
BlockDriverState *bs = child->bs;
@@ -1215,9 +1216,11 @@ static int coroutine_fn
bdrv_co_do_copy_on_readv(BdrvChild *child,
goto err;
}
- qemu_iovec_from_buf(qiov, progress, bounce_buffer + skip_bytes,
- pnum - skip_bytes);
- } else {
+ if (!(flags & BDRV_REQ_CACHE)) {
+ qemu_iovec_from_buf(qiov, progress, bounce_buffer + skip_bytes,
+ pnum - skip_bytes);
+ }
+ } else if (!(flags & BDRV_REQ_CACHE)) {
/* Read directly into the destination */
qemu_iovec_init(&local_qiov, qiov->niov);
qemu_iovec_concat(&local_qiov, qiov, progress, pnum - skip_bytes);
@@ -1268,7 +1271,8 @@ static int coroutine_fn bdrv_aligned_preadv(BdrvChild
*child,
* potential fallback support, if we ever implement any read flags
* to pass through to drivers. For now, there aren't any
* passthrough flags. */
- assert(!(flags & ~(BDRV_REQ_NO_SERIALISING | BDRV_REQ_COPY_ON_READ)));
+ assert(!(flags & ~(BDRV_REQ_NO_SERIALISING | BDRV_REQ_COPY_ON_READ |
+ BDRV_REQ_CACHE)));
/* Handle Copy on Read and associated serialisation */
if (flags & BDRV_REQ_COPY_ON_READ) {
@@ -1296,7 +1300,9 @@ static int coroutine_fn bdrv_aligned_preadv(BdrvChild
*child,
}
if (!ret || pnum != bytes) {
- ret = bdrv_co_do_copy_on_readv(child, offset, bytes, qiov);
+ ret = bdrv_co_do_copy_on_readv(child, offset, bytes, qiov, flags);
+ goto out;
+ } else if (flags & BDRV_REQ_CACHE) {
goto out;
}
}
--
2.18.0
