From efcc7a23242dd0fa05932383cf35c068d16e6bbf Mon Sep 17 00:00:00 2001 From: Paolo Bonzini Date: Tue, 8 May 2012 16:51:58 +0200 Subject: stream: do not copy unallocated sectors from the base Unallocated sectors should really never be accessed by the guest, so there's no need to copy them during the streaming process. If they are read by the guest during streaming, guest-initiated copy-on-read will copy them (we're in the base == NULL case, which enables copy on read). If they are read after we disconnect the image from the base, they will read as zeroes anyway. Signed-off-by: Paolo Bonzini Signed-off-by: Kevin Wolf --- block/stream.c | 18 ++++-------------- 1 file changed, 4 insertions(+), 14 deletions(-) (limited to 'block/stream.c') diff --git a/block/stream.c b/block/stream.c index a2c8f67711..608a860aa2 100644 --- a/block/stream.c +++ b/block/stream.c @@ -130,14 +130,9 @@ static int coroutine_fn is_allocated_base(BlockDriverState *top, */ intermediate = top->backing_hd; - while (intermediate) { + while (intermediate != base) { int pnum_inter; - /* reached base */ - if (intermediate == base) { - *pnum = n; - return 1; - } ret = bdrv_co_is_allocated(intermediate, sector_num, nb_sectors, &pnum_inter); if (ret < 0) { @@ -160,6 +155,7 @@ static int coroutine_fn is_allocated_base(BlockDriverState *top, intermediate = intermediate->backing_hd; } + *pnum = n; return 1; } @@ -203,14 +199,8 @@ wait: break; } - if (base) { - ret = is_allocated_base(bs, base, sector_num, - STREAM_BUFFER_SIZE / BDRV_SECTOR_SIZE, &n); - } else { - ret = bdrv_co_is_allocated(bs, sector_num, - STREAM_BUFFER_SIZE / BDRV_SECTOR_SIZE, - &n); - } + ret = is_allocated_base(bs, base, sector_num, + STREAM_BUFFER_SIZE / BDRV_SECTOR_SIZE, &n); trace_stream_one_iteration(s, sector_num, n, ret); if (ret == 0) { if (s->common.speed) { -- cgit v1.2.3