Re: [Qemu-block] [PATCH v2 2/4] block: support compressed write for copy-on-read

[Stefan Hajnoczi]

On Thu, Nov 16, 2017 at 07:54:56PM +0300, Anton Nefedov wrote:
> Signed-off-by: Anton Nefedov 
> Reviewed-by: Max Reitz 
> ---
>  block/io.c | 23 +--
>  block/trace-events |  2 +-
>  2 files changed, 18 insertions(+), 7 deletions(-)

Reviewed-by: Stefan Hajnoczi 


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[Qemu-block] [PATCH v2 2/4] block: support compressed write for copy-on-read

[Anton Nefedov]

Signed-off-by: Anton Nefedov 
Reviewed-by: Max Reitz 
---
 block/io.c | 23 +--
 block/trace-events |  2 +-
 2 files changed, 18 insertions(+), 7 deletions(-)

diff --git a/block/io.c b/block/io.c
index 3d5ef2c..2ba62a3 100644
--- a/block/io.c
+++ b/block/io.c
@@ -953,7 +953,7 @@ 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;
 
@@ -988,12 +988,13 @@ static int coroutine_fn 
bdrv_co_do_copy_on_readv(BdrvChild *child,
  * allocating cluster in the image file.  Note that this value may exceed
  * BDRV_REQUEST_MAX_BYTES (even when the original read did not), which
  * is one reason we loop rather than doing it all at once.
+ * Also this is crucial for compressed copy-on-read.
  */
 bdrv_round_to_clusters(bs, offset, bytes, _offset, _bytes);
 skip_bytes = offset - cluster_offset;
 
 trace_bdrv_co_do_copy_on_readv(bs, offset, bytes,
-   cluster_offset, cluster_bytes);
+   cluster_offset, cluster_bytes, flags);
 
 bounce_buffer = qemu_try_blockalign(bs,
 MIN(MIN(max_transfer, cluster_bytes),
@@ -1041,8 +1042,13 @@ static int coroutine_fn 
bdrv_co_do_copy_on_readv(BdrvChild *child,
 /* This does not change the data on the disk, it is not
  * necessary to flush even in cache=writethrough mode.
  */
-ret = bdrv_driver_pwritev(bs, cluster_offset, pnum,
-  _qiov, 0);
+if (flags & BDRV_REQ_WRITE_COMPRESSED) {
+ret = bdrv_driver_pwritev_compressed(bs, cluster_offset,
+ pnum, _qiov);
+} else {
+ret = bdrv_driver_pwritev(bs, cluster_offset, pnum,
+  _qiov, 0);
+}
 }
 
 if (ret < 0) {
@@ -1107,7 +1113,12 @@ 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_WRITE_COMPRESSED)));
+
+/* write compressed only makes sense with copy on read */
+assert(!(flags & BDRV_REQ_WRITE_COMPRESSED) ||
+   (flags & BDRV_REQ_COPY_ON_READ));
 
 /* Handle Copy on Read and associated serialisation */
 if (flags & BDRV_REQ_COPY_ON_READ) {
@@ -1132,7 +1143,7 @@ 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;
 }
 }
diff --git a/block/trace-events b/block/trace-events
index 11c8d5f..12fe188 100644
--- a/block/trace-events
+++ b/block/trace-events
@@ -12,7 +12,7 @@ blk_co_pwritev(void *blk, void *bs, int64_t offset, unsigned 
int bytes, int flag
 bdrv_co_preadv(void *bs, int64_t offset, int64_t nbytes, unsigned int flags) 
"bs %p offset %"PRId64" nbytes %"PRId64" flags 0x%x"
 bdrv_co_pwritev(void *bs, int64_t offset, int64_t nbytes, unsigned int flags) 
"bs %p offset %"PRId64" nbytes %"PRId64" flags 0x%x"
 bdrv_co_pwrite_zeroes(void *bs, int64_t offset, int count, int flags) "bs %p 
offset %"PRId64" count %d flags 0x%x"
-bdrv_co_do_copy_on_readv(void *bs, int64_t offset, unsigned int bytes, int64_t 
cluster_offset, int64_t cluster_bytes) "bs %p offset %"PRId64" bytes %u 
cluster_offset %"PRId64" cluster_bytes %"PRId64
+bdrv_co_do_copy_on_readv(void *bs, int64_t offset, unsigned int bytes, int64_t 
cluster_offset, int64_t cluster_bytes, int flags) "bs %p offset %"PRId64" bytes 
%u cluster_offset %"PRId64" cluster_bytes %"PRId64" flags 0x%x"
 
 # block/stream.c
 stream_one_iteration(void *s, int64_t offset, uint64_t bytes, int 
is_allocated) "s %p offset %" PRId64 " bytes %" PRIu64 " is_allocated %d"
-- 
2.7.4