Re: [PATCH v11 05/13] copy-on-read: limit COR operations to base in COR driver

Limit COR operations by the base node in the backing chain when the overlay base node name is given. It will be useful for a block stream job when the COR-filter is applied. The overlay base node is passed as the base itself may change due to concurrent commit jobs on the same backing chain. Signed-off-by: Andrey Shinkevich <andrey.shinkevich(a)virtuozzo.com&gt; --- block/copy-on-read.c | 39 +++++++++++++++++++++++++++++++++++++-- 1 file changed, 37 insertions(+), 2 deletions(-) diff --git a/block/copy-on-read.c b/block/copy-on-read.c index c578b1b..dfbd6ad 100644 --- a/block/copy-on-read.c +++ b/block/copy-on-read.c @@ -122,8 +122,43 @@ 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; + int64_t size = offset + bytes;

+ int local_flags; + int ret; + BDRVStateCOR *state = bs->opaque; + + if (!state->base_overlay) { + return bdrv_co_preadv_part(bs->file, offset, bytes, qiov, qiov_offset, + flags | BDRV_REQ_COPY_ON_READ); + } + + while (offset < size) {

+ local_flags = flags; + + /* In case of failure, try to copy-on-read anyway */ + ret = bdrv_is_allocated(bs->file->bs, offset, bytes, &n); + if (!ret) { + ret = bdrv_is_allocated_above(bdrv_cow_bs(bs->file->bs), + state->base_overlay, true, offset, + n, &n); + if (ret) { + local_flags |= BDRV_REQ_COPY_ON_READ; + } + }

+ + 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; }