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[Qemu-devel] [PATCH for-2.6 1/2] block/mirror: Revive dead yielding code
From: |
Max Reitz |
Subject: |
[Qemu-devel] [PATCH for-2.6 1/2] block/mirror: Revive dead yielding code |
Date: |
Wed, 20 Apr 2016 00:59:47 +0200 |
mirror_iteration() is supposed to wait if the current chunk is subject
to a still in-flight mirroring operation. However, it mixed checking
this conflict situation with checking the dirty status of a chunk. A
simplification for the latter condition (the first chunk encountered is
always dirty) led to neglecting the former: We just skip the first chunk
and thus never test whether it conflicts with an in-flight operation.
To fix this, pull out the code which waits for in-flight operations on
the first chunk of the range to be mirrored to settle.
Signed-off-by: Max Reitz <address@hidden>
---
block/mirror.c | 23 ++++++++++++-----------
1 file changed, 12 insertions(+), 11 deletions(-)
diff --git a/block/mirror.c b/block/mirror.c
index c2cfc1a..2714a77 100644
--- a/block/mirror.c
+++ b/block/mirror.c
@@ -298,7 +298,7 @@ static void mirror_do_zero_or_discard(MirrorBlockJob *s,
static uint64_t coroutine_fn mirror_iteration(MirrorBlockJob *s)
{
BlockDriverState *source = s->common.bs;
- int64_t sector_num;
+ int64_t sector_num, first_chunk;
uint64_t delay_ns = 0;
/* At least the first dirty chunk is mirrored in one iteration. */
int nb_chunks = 1;
@@ -313,6 +313,12 @@ static uint64_t coroutine_fn
mirror_iteration(MirrorBlockJob *s)
assert(sector_num >= 0);
}
+ first_chunk = sector_num / sectors_per_chunk;
+ while (test_bit(first_chunk, s->in_flight_bitmap)) {
+ trace_mirror_yield_in_flight(s, first_chunk, s->in_flight);
+ mirror_wait_for_io(s);
+ }
+
/* Find the number of consective dirty chunks following the first dirty
* one, and wait for in flight requests in them. */
while (nb_chunks * sectors_per_chunk < (s->buf_size >> BDRV_SECTOR_BITS)) {
@@ -324,17 +330,12 @@ static uint64_t coroutine_fn
mirror_iteration(MirrorBlockJob *s)
break;
}
if (test_bit(next_chunk, s->in_flight_bitmap)) {
- if (nb_chunks > 0) {
- break;
- }
- trace_mirror_yield_in_flight(s, next_sector, s->in_flight);
- mirror_wait_for_io(s);
- /* Now retry. */
- } else {
- hbitmap_next = hbitmap_iter_next(&s->hbi);
- assert(hbitmap_next == next_sector);
- nb_chunks++;
+ break;
}
+
+ hbitmap_next = hbitmap_iter_next(&s->hbi);
+ assert(hbitmap_next == next_sector);
+ nb_chunks++;
}
/* Clear dirty bits before querying the block status, because
--
2.8.0