Some storages(i.e. librbd) already have interfaces to handle some SCSI
commands directly. This patch adds COMPARE_AND_WRITE command support
through the write path in the block io layer by introducing a new element
BDRV_REQ_COMPARE_AND_WRITE into BdrvRequestFlags which indicates a
COMPARE_AND_WRITE request. In this way we could easily extend to other
SCSI commands support like WRITE_SAME in the future.
Signed-off-by: Yaowei Bai <baiyao...@cmss.chinamobile.com>
---
block/io.c | 20 ++++++++++++++++++++
include/block/block.h | 5 +++--
include/block/block_int.h | 3 +++
3 files changed, 26 insertions(+), 2 deletions(-)
diff --git a/block/io.c b/block/io.c
index f75777f..3507d71 100644
--- a/block/io.c
+++ b/block/io.c
@@ -1186,6 +1186,26 @@ static int coroutine_fn
bdrv_driver_pwritev(BlockDriverState *bs,
goto emulate_flags;
}
+ if (drv->bdrv_aio_compare_and_write &&
+ (flags & BDRV_REQ_COMPARE_AND_WRITE)) {
+ BlockAIOCB *acb;
+ CoroutineIOCompletion co = {
+ .coroutine = qemu_coroutine_self(),
+ };
+
+ acb = drv->bdrv_aio_compare_and_write(bs, offset, bytes, qiov,
+ flags & bs->supported_write_flags,
+ bdrv_co_io_em_complete, &co);
+ flags &= ~bs->supported_write_flags;
+ if (acb == NULL) {
+ ret = -EIO;
+ } else {
+ qemu_coroutine_yield();
+ ret = co.ret;
+ }
+ goto emulate_flags;
+ }
+
if (drv->bdrv_aio_pwritev) {
BlockAIOCB *acb;
CoroutineIOCompletion co = {
diff --git a/include/block/block.h b/include/block/block.h
index 1df9848..f71aa4f 100644
--- a/include/block/block.h
+++ b/include/block/block.h
@@ -92,9 +92,10 @@ typedef enum {
* on read request and means that caller doesn't really need data to be
* written to qiov parameter which may be NULL.
*/
- BDRV_REQ_PREFETCH = 0x200,
+ BDRV_REQ_PREFETCH = 0x200,
+ BDRV_REQ_COMPARE_AND_WRITE = 0x400,
/* Mask of valid flags */
- BDRV_REQ_MASK = 0x3ff,
+ BDRV_REQ_MASK = 0x7ff,
} BdrvRequestFlags;
typedef struct BlockSizes {
diff --git a/include/block/block_int.h b/include/block/block_int.h
index dd033d0..96096e0 100644
--- a/include/block/block_int.h
+++ b/include/block/block_int.h
@@ -189,6 +189,9 @@ struct BlockDriver {
BlockAIOCB *(*bdrv_aio_pdiscard)(BlockDriverState *bs,
int64_t offset, int bytes,
BlockCompletionFunc *cb, void *opaque);
+ BlockAIOCB *(*bdrv_aio_compare_and_write)(BlockDriverState *bs,
+ uint64_t offset, uint64_t bytes, QEMUIOVector *qiov, int flags,
+ BlockCompletionFunc *cb, void *opaque);
int coroutine_fn (*bdrv_co_readv)(BlockDriverState *bs,
int64_t sector_num, int nb_sectors, QEMUIOVector *qiov);
--
1.8.3.1
