diff options
| -rw-r--r-- | block/stream.c | 51 |
1 files changed, 25 insertions, 26 deletions
diff --git a/block/stream.c b/block/stream.c index 8e5832273b..4490a25ba2 100644 --- a/block/stream.c +++ b/block/stream.c @@ -101,45 +101,33 @@ static void close_unused_images(BlockDriverState *top, BlockDriverState *base, /* * Given an image chain: [BASE] -> [INTER1] -> [INTER2] -> [TOP] * - * Return true if the given sector is allocated in top. - * Return false if the given sector is allocated in intermediate images. - * Return true otherwise. + * Return true if the given sector is allocated in any image between + * BASE and TOP (inclusive). BASE can be NULL to check if the given + * sector is allocated in any image of the chain. Return false otherwise. * * 'pnum' is set to the number of sectors (including and immediately following * the specified sector) that are known to be in the same * allocated/unallocated state. * */ -static int coroutine_fn is_allocated_base(BlockDriverState *top, - BlockDriverState *base, - int64_t sector_num, - int nb_sectors, int *pnum) +static int coroutine_fn is_allocated_above(BlockDriverState *top, + BlockDriverState *base, + int64_t sector_num, + int nb_sectors, int *pnum) { BlockDriverState *intermediate; - int ret, n; - - ret = bdrv_co_is_allocated(top, sector_num, nb_sectors, &n); - if (ret) { - *pnum = n; - return ret; - } - - /* - * Is the unallocated chunk [sector_num, n] also - * unallocated between base and top? - */ - intermediate = top->backing_hd; + int ret, n = nb_sectors; + intermediate = top; while (intermediate != base) { int pnum_inter; - ret = bdrv_co_is_allocated(intermediate, sector_num, nb_sectors, &pnum_inter); if (ret < 0) { return ret; } else if (ret) { *pnum = pnum_inter; - return 0; + return 1; } /* @@ -156,7 +144,7 @@ static int coroutine_fn is_allocated_base(BlockDriverState *top, } *pnum = n; - return 1; + return 0; } static void coroutine_fn stream_run(void *opaque) @@ -189,6 +177,7 @@ static void coroutine_fn stream_run(void *opaque) for (sector_num = 0; sector_num < end; sector_num += n) { uint64_t delay_ns = 0; + bool copy; wait: /* Note that even when no rate limit is applied we need to yield @@ -199,10 +188,20 @@ wait: break; } - ret = is_allocated_base(bs, base, sector_num, - STREAM_BUFFER_SIZE / BDRV_SECTOR_SIZE, &n); + ret = bdrv_co_is_allocated(bs, sector_num, + STREAM_BUFFER_SIZE / BDRV_SECTOR_SIZE, &n); + if (ret == 1) { + /* Allocated in the top, no need to copy. */ + copy = false; + } else { + /* Copy if allocated in the intermediate images. Limit to the + * known-unallocated area [sector_num, sector_num+n). */ + ret = is_allocated_above(bs->backing_hd, base, sector_num, n, &n); + copy = (ret == 1); + } + trace_stream_one_iteration(s, sector_num, n, ret); - if (ret == 0) { + if (ret >= 0 && copy) { if (s->common.speed) { delay_ns = ratelimit_calculate_delay(&s->limit, n); if (delay_ns > 0) { |