Add the new member supported_read_flags to the BlockDriverState structure. It will control the flags set for copy-on-read operations. Make the block generic layer evaluate supported read flags before they go to a block driver.
Suggested-by: Vladimir Sementsov-Ogievskiy <vsement...@virtuozzo.com> Signed-off-by: Andrey Shinkevich <andrey.shinkev...@virtuozzo.com> --- block/io.c | 12 ++++++++++-- include/block/block_int.h | 4 ++++ 2 files changed, 14 insertions(+), 2 deletions(-) diff --git a/block/io.c b/block/io.c index 54f0968..78ddf13 100644 --- a/block/io.c +++ b/block/io.c @@ -1392,6 +1392,9 @@ static int coroutine_fn bdrv_aligned_preadv(BdrvChild *child, if (flags & BDRV_REQ_COPY_ON_READ) { int64_t pnum; + /* The flag BDRV_REQ_COPY_ON_READ has reached its addressee */ + flags &= ~BDRV_REQ_COPY_ON_READ; + ret = bdrv_is_allocated(bs, offset, bytes, &pnum); if (ret < 0) { goto out; @@ -1413,9 +1416,13 @@ static int coroutine_fn bdrv_aligned_preadv(BdrvChild *child, goto out; } + if (flags & ~bs->supported_read_flags) { + abort(); + } + 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); goto out; } @@ -1428,7 +1435,8 @@ static int coroutine_fn bdrv_aligned_preadv(BdrvChild *child, ret = bdrv_driver_preadv(bs, offset + bytes - bytes_remaining, num, qiov, - qiov_offset + bytes - bytes_remaining, 0); + qiov_offset + bytes - bytes_remaining, + flags); max_bytes -= num; } else { num = bytes_remaining; diff --git a/include/block/block_int.h b/include/block/block_int.h index f782737..474174c 100644 --- a/include/block/block_int.h +++ b/include/block/block_int.h @@ -873,6 +873,10 @@ struct BlockDriverState { /* I/O Limits */ BlockLimits bl; + /* + * Flags honored during pread + */ + unsigned int supported_read_flags; /* Flags honored during pwrite (so far: BDRV_REQ_FUA, * BDRV_REQ_WRITE_UNCHANGED). * If a driver does not support BDRV_REQ_WRITE_UNCHANGED, those -- 1.8.3.1