On 12.10.20 19:43, Andrey Shinkevich wrote:
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@virtuozzo.com>
---
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) &
How about dropping the double negation and using a logical && instead of
the binary &?
+ !(local_flags & BDRV_REQ_COPY_ON_READ)) {
+ /* Skip non-guest reads if no copy needed */
+ } else {
Hm. I would have just written the negated form
(!(flags & BDRV_REQ_PREFETCH) || (local_flags & BDRV_REQ_COPY_ON_READ))
and put the “skip” comment above that condition.
(Since local_flags is initialized to flags, it can be written as a
single comparison, but that’s a matter of taste and I’m not going to
recommend either over the other:
((local_flags & (BDRV_REQ_PREFETCH | BDRV_REQ_COPY_ON_READ)) !=
BDRV_REQ_PREFETCH)
)
+ 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);