From a0abf124d19384e05702973bb3706e881fcef5d3 Mon Sep 17 00:00:00 2001 Message-Id: In-Reply-To: References: From: Stefan Hajnoczi Date: Fri, 6 Sep 2013 18:12:24 +0200 Subject: [PATCH 04/25] stream: complete early if end of backing file is reached It is possible to create an image that is larger than its backing file. Reading beyond the end of the backing file produces zeroes if no writes have been made to those sectors in the image file. This patch finishes streaming early when the end of the backing file is reached. Without this patch the block job hangs and continually tries to stream the first sectors beyond the end of the backing file. To reproduce the hung block job bug: $ qemu-img create -f qcow2 backing.qcow2 128M $ qemu-img create -f qcow2 -o backing_file=backing.qcow2 image.qcow2 6G $ qemu -drive if=virtio,cache=none,file=image.qcow2 (qemu) block_stream virtio0 (qemu) info block-jobs The qemu-iotests 030 streaming test still passes. Signed-off-by: Stefan Hajnoczi Reviewed-by: Paolo Bonzini Signed-off-by: Kevin Wolf (cherry picked from commit 571cd9dcc7f2fee59e47913365ced7781f33c2d3) Signed-off-by: Michal Novotny --- block/stream.c | 6 ++++++ 1 file changed, 6 insertions(+) diff --git a/block/stream.c b/block/stream.c index f03c934..4043d9d 100644 --- a/block/stream.c +++ b/block/stream.c @@ -149,6 +149,12 @@ wait: * known-unallocated area [sector_num, sector_num+n). */ ret = bdrv_co_is_allocated_above(bs->backing_hd, base, sector_num, n, &n); + + /* Finish early if end of backing file has been reached */ + if (ret == 0 && n == 0) { + n = end - sector_num; + } + copy = (ret == 1); } trace_stream_one_iteration(s, sector_num, n, ret); -- 1.7.11.7