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block/mirror: Revive dead yielding code 

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 <mreitz@redhat.com>
Reviewed-by: Fam Zheng <famz@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
This commit is contained in:
Max Reitz 2016-04-20 00:59:47 +02:00 committed by Kevin Wolf
parent 4113b0532d
commit 9c83625bdd
1 changed files with 12 additions and 11 deletions
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23
block/mirror.c
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@ -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