22.10.2020 21:13, Andrey Shinkevich wrote:
Limit COR operations to the bottom node (inclusively) in the backing
chain when the bottom node name is given. It will be useful for a block
stream job when the COR-filter is applied. The bottom node is passed as
the base itself may change due to concurrent commit jobs on the same
backing chain.
Signed-off-by: Andrey Shinkevich
---
block/copy-on-read.c | 42 --
1 file changed, 40 insertions(+), 2 deletions(-)
diff --git a/block/copy-on-read.c b/block/copy-on-read.c
index 3d8e4db..8178a91 100644
--- a/block/copy-on-read.c
+++ b/block/copy-on-read.c
@@ -123,8 +123,46 @@ static int coroutine_fn
cor_co_preadv_part(BlockDriverState *bs,
size_t qiov_offset,
int flags)
{
-return bdrv_co_preadv_part(bs->file, offset, bytes, qiov, qiov_offset,
- flags | BDRV_REQ_COPY_ON_READ);
+int64_t n = 0;
no need to initialize n actually.
+int local_flags;
+int ret;
+BDRVStateCOR *state = bs->opaque;
+
+if (!state->bottom_bs) {
+return bdrv_co_preadv_part(bs->file, offset, bytes, qiov, qiov_offset,
+ flags | BDRV_REQ_COPY_ON_READ);
+}
+
+while (bytes) {
+local_flags = flags;
+
+/* In case of failure, try to copy-on-read anyway */
+ret = bdrv_is_allocated(bs->file->bs, offset, bytes, );
+if (!ret || ret < 0) {
simper: if (ret <= 0) {
+ret =
bdrv_is_allocated_above(bdrv_backing_chain_next(bs->file->bs),
+ state->bottom_bs, true, offset,
+ n, );
+if (ret == 1 || ret < 0) {
+local_flags |= BDRV_REQ_COPY_ON_READ;
+}
+/* Finish earlier if the end of a backing file has been reached */
+if (ret == 0 && n == 0) {
"n == 0" should be enough
+break;
+}
+}
+
+ret = bdrv_co_preadv_part(bs->file, offset, n, qiov, qiov_offset,
+ local_flags);
+if (ret < 0) {
+return ret;
+}
+
+offset += n;
+qiov_offset += n;
+bytes -= n;
+}
+
+return 0;
}
My remarks are minor, so:
Reviewed-by: Vladimir Sementsov-Ogievskiy
And yes, I still think that this is good to be merged with two previous patches.
--
Best regards,
Vladimir
