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[Qemu-devel] [PATCH 1.1 17/22] stream: fix ratelimiting corner case
From: |
Paolo Bonzini |
Subject: |
[Qemu-devel] [PATCH 1.1 17/22] stream: fix ratelimiting corner case |
Date: |
Tue, 8 May 2012 16:51:57 +0200 |
This fixes inability to make progress in streaming if the quota is set
to less than the amount of data that an I/O operation has to write.
In this case, limit->dispatched + n will always be above the quota and,
due to the "goto retry" to recheck cancellation and allocation, streaming
will livelock.
This can be reproduced with "block_job_set_speed ide0-hd0 1b". Of course,
with this patch the requested limit will not be obeyed. That could be
done with another patch that caps is_allocated's n argument by the slice
quota.
Signed-off-by: Paolo Bonzini <address@hidden>
---
block/stream.c | 10 +++++-----
1 file changed, 5 insertions(+), 5 deletions(-)
diff --git a/block/stream.c b/block/stream.c
index 25f98e4..a2c8f67 100644
--- a/block/stream.c
+++ b/block/stream.c
@@ -33,19 +33,19 @@ typedef struct {
static int64_t ratelimit_calculate_delay(RateLimit *limit, uint64_t n)
{
- int64_t delay_ns = 0;
int64_t now = qemu_get_clock_ns(rt_clock);
if (limit->next_slice_time < now) {
limit->next_slice_time = now + SLICE_TIME;
limit->dispatched = 0;
}
- if (limit->dispatched + n > limit->slice_quota) {
- delay_ns = limit->next_slice_time - now;
- } else {
+ if (limit->dispatched == 0 || limit->dispatched + n <= limit->slice_quota)
{
limit->dispatched += n;
+ return 0;
+ } else {
+ limit->dispatched = n;
+ return limit->next_slice_time - now;
}
- return delay_ns;
}
static void ratelimit_set_speed(RateLimit *limit, uint64_t speed)
--
1.7.10.1
- Re: [Qemu-devel] [PATCH 1.1 04/22] block: fully delete bs->file when closing, (continued)
- [Qemu-devel] [PATCH 1.1 06/22] block: wait for job callback in block_job_cancel_sync, Paolo Bonzini, 2012/05/08
- [Qemu-devel] [PATCH 1.1 07/22] block: simplify path_is_absolute, Paolo Bonzini, 2012/05/08
- [Qemu-devel] [PATCH 1.1 09/22] block: move field reset from bdrv_open_common to bdrv_close, Paolo Bonzini, 2012/05/08
- [Qemu-devel] [PATCH 1.1 08/22] block: protect path_has_protocol from filenames with colons, Paolo Bonzini, 2012/05/08
- [Qemu-devel] [PATCH 1.1 10/22] qemu-img: make "info" backing file output correct and easier to use, Paolo Bonzini, 2012/05/08
- [Qemu-devel] [PATCH 1.1 13/22] stream: fix sectors not allocated test, Paolo Bonzini, 2012/05/08
- [Qemu-devel] [PATCH 1.1 16/22] stream: fix HMP block_job_set_speed, Paolo Bonzini, 2012/05/08
- [Qemu-devel] [PATCH 1.1 14/22] stream: add testcase for partial streaming, Paolo Bonzini, 2012/05/08
- [Qemu-devel] [PATCH 1.1 15/22] stream: pass new base image format to bdrv_change_backing_file, Paolo Bonzini, 2012/05/08
- [Qemu-devel] [PATCH 1.1 17/22] stream: fix ratelimiting corner case,
Paolo Bonzini <=
- [Qemu-devel] [PATCH 1.1 18/22] stream: do not copy unallocated sectors from the base, Paolo Bonzini, 2012/05/08
- [Qemu-devel] [PATCH 1.1 20/22] stream: tweak usage of bdrv_co_is_allocated, Paolo Bonzini, 2012/05/08
- [Qemu-devel] [PATCH 1.1 21/22] stream: move is_allocated_above to block.c, Paolo Bonzini, 2012/05/08
- [Qemu-devel] [PATCH 1.1 22/22] stream: move rate limiting to a separate header file, Paolo Bonzini, 2012/05/08
- [Qemu-devel] [PATCH 1.1 11/22] qemu-io: correctly print non-integer values as decimals, Paolo Bonzini, 2012/05/08
- [Qemu-devel] [PATCH 1.1 19/22] block: implement is_allocated for raw, Paolo Bonzini, 2012/05/08