[PATCH v11 09/13] copy-on-read: skip non-guest reads if no copy needed

[Andrey Shinkevich <andrey.shinkevich@xxxxxxxxxxxxx>]

If the flag BDRV_REQ_PREFETCH was set, pass it further to the
COR-driver to skip unneeded reading. It can be taken into account for
the COR-algorithms optimization. That check is being made during the
block stream job by the moment.

Signed-off-by: Andrey Shinkevich <andrey.shinkevich@xxxxxxxxxxxxx>
---
 block/copy-on-read.c | 13 +++++++++----
 block/io.c           |  3 ++-
 2 files changed, 11 insertions(+), 5 deletions(-)

diff --git a/block/copy-on-read.c b/block/copy-on-read.c
index b136895..278a11a 100644
--- a/block/copy-on-read.c
+++ b/block/copy-on-read.c
@@ -148,10 +148,15 @@ static int coroutine_fn cor_co_preadv_part(BlockDriverState *bs,
             }
         }
 
-        ret = bdrv_co_preadv_part(bs->file, offset, n, qiov, qiov_offset,
-                                  local_flags);
-        if (ret < 0) {
-            return ret;
+        if (!!(flags & BDRV_REQ_PREFETCH) &
+            !(local_flags & BDRV_REQ_COPY_ON_READ)) {
+            /* Skip non-guest reads if no copy needed */
+        } else {
+            ret = bdrv_co_preadv_part(bs->file, offset, n, qiov, qiov_offset,
+                                      local_flags);
+            if (ret < 0) {
+                return ret;
+            }
         }
 
         offset += n;
diff --git a/block/io.c b/block/io.c
index 11df188..bff1808 100644
--- a/block/io.c
+++ b/block/io.c
@@ -1512,7 +1512,8 @@ static int coroutine_fn bdrv_aligned_preadv(BdrvChild *child,
 
     max_bytes = ROUND_UP(MAX(0, total_bytes - offset), align);
     if (bytes <= max_bytes && bytes <= max_transfer) {
-        ret = bdrv_driver_preadv(bs, offset, bytes, qiov, qiov_offset, 0);
+        ret = bdrv_driver_preadv(bs, offset, bytes, qiov, qiov_offset,
+                                 flags & bs->supported_read_flags);
         goto out;
     }
 
-- 
1.8.3.1