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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>
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@ -298,7 +298,7 @@ static void mirror_do_zero_or_discard(MirrorBlockJob *s,
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static uint64_t coroutine_fn mirror_iteration(MirrorBlockJob *s)
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{
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BlockDriverState *source = s->common.bs;
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int64_t sector_num;
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int64_t sector_num, first_chunk;
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uint64_t delay_ns = 0;
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/* At least the first dirty chunk is mirrored in one iteration. */
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int nb_chunks = 1;
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@ -313,6 +313,12 @@ static uint64_t coroutine_fn mirror_iteration(MirrorBlockJob *s)
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assert(sector_num >= 0);
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}
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first_chunk = sector_num / sectors_per_chunk;
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while (test_bit(first_chunk, s->in_flight_bitmap)) {
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trace_mirror_yield_in_flight(s, first_chunk, s->in_flight);
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mirror_wait_for_io(s);
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}
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/* Find the number of consective dirty chunks following the first dirty
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* one, and wait for in flight requests in them. */
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while (nb_chunks * sectors_per_chunk < (s->buf_size >> BDRV_SECTOR_BITS)) {
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@ -324,17 +330,12 @@ static uint64_t coroutine_fn mirror_iteration(MirrorBlockJob *s)
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break;
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}
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if (test_bit(next_chunk, s->in_flight_bitmap)) {
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if (nb_chunks > 0) {
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break;
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}
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trace_mirror_yield_in_flight(s, next_sector, s->in_flight);
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mirror_wait_for_io(s);
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/* Now retry. */
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} else {
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hbitmap_next = hbitmap_iter_next(&s->hbi);
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assert(hbitmap_next == next_sector);
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nb_chunks++;
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break;
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}
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hbitmap_next = hbitmap_iter_next(&s->hbi);
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assert(hbitmap_next == next_sector);
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nb_chunks++;
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}
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/* Clear dirty bits before querying the block status, because
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