From 029d091e4975af60ff9622717af19c5910f2f4e9 Mon Sep 17 00:00:00 2001 From: Peter Lieven Date: Fri, 11 Jan 2013 13:29:55 +0100 Subject: [PATCH] block: fix initialization in bdrv_io_limits_enable() bdrv_io_limits_enable() starts a new slice, but does not set io_base correctly for that slice. Here is how io_base is used: bytes_base = bs->nr_bytes[is_write] - bs->io_base.bytes[is_write]; bytes_res = (unsigned) nb_sectors * BDRV_SECTOR_SIZE; if (bytes_base + bytes_res <= bytes_limit) { /* no wait */ } else { /* operation needs to be throttled */ } As a result, any I/O operations that are triggered between now and bs->slice_end are incorrectly limited. If 10 MB of data has been written since the VM was started, QEMU thinks that 10 MB of data has been written in this slice. This leads to a I/O lockup in the guest. We fix this by delaying the start of a new slice to the next call of bdrv_exceed_io_limits(). Signed-off-by: Peter Lieven Reviewed-by: Paolo Bonzini Signed-off-by: Stefan Hajnoczi --- block.c | 4 ---- 1 file changed, 4 deletions(-) diff --git a/block.c b/block.c index b5e64ecf11..4a90dd1a78 100644 --- a/block.c +++ b/block.c @@ -155,10 +155,6 @@ void bdrv_io_limits_enable(BlockDriverState *bs) { qemu_co_queue_init(&bs->throttled_reqs); bs->block_timer = qemu_new_timer_ns(vm_clock, bdrv_block_timer, bs); - bs->slice_time = 5 * BLOCK_IO_SLICE_TIME; - bs->slice_start = qemu_get_clock_ns(vm_clock); - bs->slice_end = bs->slice_start + bs->slice_time; - memset(&bs->io_base, 0, sizeof(bs->io_base)); bs->io_limits_enabled = true; }