[PATCH v2 4/6] block: support compressed write for copy-on-read

[Andrey Shinkevich <andrey.shinkevich@virtuozzo.com>]

Support the data compression during block-stream job over a backup
backing chain implemented in the following patch 'block-stream:
add compress option'.

Signed-off-by: Anton Nefedov <anton.nefedov@virtuozzo.com>
Signed-off-by: Denis V. Lunev <den@openvz.org>
Signed-off-by: Andrey Shinkevich <andrey.shinkevich@virtuozzo.com>
---
 block/io.c         | 21 ++++++++++++++++-----
 block/trace-events |  2 +-
 2 files changed, 17 insertions(+), 6 deletions(-)

diff --git a/block/io.c b/block/io.c
index f8c3596..a7cd24f 100644
--- a/block/io.c
+++ b/block/io.c
@@ -1264,12 +1264,13 @@ 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, &cluster_offset, &cluster_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);
 
     while (cluster_bytes) {
         int64_t pnum;
@@ -1328,9 +1329,15 @@ 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,
-                                          &local_qiov, 0,
-                                          BDRV_REQ_WRITE_UNCHANGED);
+                if (flags & BDRV_REQ_WRITE_COMPRESSED) {
+                    ret = bdrv_driver_pwritev_compressed(bs, cluster_offset,
+                                                         pnum, &local_qiov,
+                                                         qiov_offset);
+                } else {
+                    ret = bdrv_driver_pwritev(bs, cluster_offset, pnum,
+                                              &local_qiov, 0,
+                                              BDRV_REQ_WRITE_UNCHANGED);
+                }
             }
 
             if (ret < 0) {
@@ -1396,7 +1403,11 @@ static int coroutine_fn bdrv_aligned_preadv(BdrvChild *child,
      * to pass through to drivers.  For now, there aren't any
      * passthrough flags.  */
     assert(!(flags & ~(BDRV_REQ_NO_SERIALISING | BDRV_REQ_COPY_ON_READ |
-                       BDRV_REQ_PREFETCH)));
+                       BDRV_REQ_PREFETCH | 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) {
diff --git a/block/trace-events b/block/trace-events
index 3aa27e6..f444548 100644
--- a/block/trace-events
+++ b/block/trace-events
@@ -14,7 +14,7 @@ blk_root_detach(void *child, void *blk, void *bs) "child %p blk %p bs %p"
 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"
 bdrv_co_copy_range_from(void *src, uint64_t src_offset, void *dst, uint64_t dst_offset, uint64_t bytes, int read_flags, int write_flags) "src %p offset %"PRIu64" dst %p offset %"PRIu64" bytes %"PRIu64" rw flags 0x%x 0x%x"
 bdrv_co_copy_range_to(void *src, uint64_t src_offset, void *dst, uint64_t dst_offset, uint64_t bytes, int read_flags, int write_flags) "src %p offset %"PRIu64" dst %p offset %"PRIu64" bytes %"PRIu64" rw flags 0x%x 0x%x"
 
-- 
1.8.3.1