From e5b43573e28b226621ac6ed9ad71e1a72d71922d Mon Sep 17 00:00:00 2001 From: Fam Zheng Date: Fri, 5 Feb 2016 10:00:29 +0800 Subject: mirror: Rewrite mirror_iteration The "pnum < nb_sectors" condition in deciding whether to actually copy data is unnecessarily strict, and the qiov initialization is unnecessarily for bdrv_aio_write_zeroes and bdrv_aio_discard. Rewrite mirror_iteration to fix both flaws. The output of iotests 109 is updated because we now report the offset and len slightly differently in mirroring progress. Signed-off-by: Fam Zheng Reviewed-by: Max Reitz Message-id: 1454637630-10585-2-git-send-email-famz@redhat.com Signed-off-by: Jeff Cody --- block/mirror.c | 335 ++++++++++++++++++++++++++++++++++----------------------- 1 file changed, 203 insertions(+), 132 deletions(-) (limited to 'block/mirror.c') diff --git a/block/mirror.c b/block/mirror.c index 2c0edfa..48cd0b3 100644 --- a/block/mirror.c +++ b/block/mirror.c @@ -47,7 +47,6 @@ typedef struct MirrorBlockJob { BlockdevOnError on_source_error, on_target_error; bool synced; bool should_complete; - int64_t sector_num; int64_t granularity; size_t buf_size; int64_t bdev_length; @@ -64,6 +63,8 @@ typedef struct MirrorBlockJob { int ret; bool unmap; bool waiting_for_io; + int target_cluster_sectors; + int max_iov; } MirrorBlockJob; typedef struct MirrorOp { @@ -159,116 +160,79 @@ static void mirror_read_complete(void *opaque, int ret) mirror_write_complete, op); } -static uint64_t coroutine_fn mirror_iteration(MirrorBlockJob *s) +/* Round sector_num and/or nb_sectors to target cluster if COW is needed, and + * return the offset of the adjusted tail sector against original. */ +static int mirror_cow_align(MirrorBlockJob *s, + int64_t *sector_num, + int *nb_sectors) { - BlockDriverState *source = s->common.bs; - int nb_sectors, sectors_per_chunk, nb_chunks, max_iov; - int64_t end, sector_num, next_chunk, next_sector, hbitmap_next_sector; - uint64_t delay_ns = 0; - MirrorOp *op; - int pnum; - int64_t ret; - BlockDriverState *file; + bool need_cow; + int ret = 0; + int chunk_sectors = s->granularity >> BDRV_SECTOR_BITS; + int64_t align_sector_num = *sector_num; + int align_nb_sectors = *nb_sectors; + int max_sectors = chunk_sectors * s->max_iov; + + need_cow = !test_bit(*sector_num / chunk_sectors, s->cow_bitmap); + need_cow |= !test_bit((*sector_num + *nb_sectors - 1) / chunk_sectors, + s->cow_bitmap); + if (need_cow) { + bdrv_round_to_clusters(s->target, *sector_num, *nb_sectors, + &align_sector_num, &align_nb_sectors); + } + + if (align_nb_sectors > max_sectors) { + align_nb_sectors = max_sectors; + if (need_cow) { + align_nb_sectors = QEMU_ALIGN_DOWN(align_nb_sectors, + s->target_cluster_sectors); + } + } - max_iov = MIN(source->bl.max_iov, s->target->bl.max_iov); + ret = align_sector_num + align_nb_sectors - (*sector_num + *nb_sectors); + *sector_num = align_sector_num; + *nb_sectors = align_nb_sectors; + assert(ret >= 0); + return ret; +} - s->sector_num = hbitmap_iter_next(&s->hbi); - if (s->sector_num < 0) { - bdrv_dirty_iter_init(s->dirty_bitmap, &s->hbi); - s->sector_num = hbitmap_iter_next(&s->hbi); - trace_mirror_restart_iter(s, bdrv_get_dirty_count(s->dirty_bitmap)); - assert(s->sector_num >= 0); - } +/* Submit async read while handling COW. + * Returns: nb_sectors if no alignment is necessary, or + * (new_end - sector_num) if tail is rounded up or down due to + * alignment or buffer limit. + */ +static int mirror_do_read(MirrorBlockJob *s, int64_t sector_num, + int nb_sectors) +{ + BlockDriverState *source = s->common.bs; + int sectors_per_chunk, nb_chunks; + int ret = nb_sectors; + MirrorOp *op; - hbitmap_next_sector = s->sector_num; - sector_num = s->sector_num; sectors_per_chunk = s->granularity >> BDRV_SECTOR_BITS; - end = s->bdev_length / BDRV_SECTOR_SIZE; - /* Extend the QEMUIOVector to include all adjacent blocks that will - * be copied in this operation. - * - * We have to do this if we have no backing file yet in the destination, - * and the cluster size is very large. Then we need to do COW ourselves. - * The first time a cluster is copied, copy it entirely. Note that, - * because both the granularity and the cluster size are powers of two, - * the number of sectors to copy cannot exceed one cluster. - * - * We also want to extend the QEMUIOVector to include more adjacent - * dirty blocks if possible, to limit the number of I/O operations and - * run efficiently even with a small granularity. - */ - nb_chunks = 0; - nb_sectors = 0; - next_sector = sector_num; - next_chunk = sector_num / sectors_per_chunk; + /* We can only handle as much as buf_size at a time. */ + nb_sectors = MIN(s->buf_size >> BDRV_SECTOR_BITS, nb_sectors); + assert(nb_sectors); + + if (s->cow_bitmap) { + ret += mirror_cow_align(s, §or_num, &nb_sectors); + } + assert(nb_sectors << BDRV_SECTOR_BITS <= s->buf_size); + /* The sector range must meet granularity because: + * 1) Caller passes in aligned values; + * 2) mirror_cow_align is used only when target cluster is larger. */ + assert(!(nb_sectors % sectors_per_chunk)); + assert(!(sector_num % sectors_per_chunk)); + nb_chunks = nb_sectors / sectors_per_chunk; - /* Wait for I/O to this cluster (from a previous iteration) to be done. */ - while (test_bit(next_chunk, s->in_flight_bitmap)) { + while (s->buf_free_count < nb_chunks) { trace_mirror_yield_in_flight(s, sector_num, s->in_flight); s->waiting_for_io = true; qemu_coroutine_yield(); s->waiting_for_io = false; } - do { - int added_sectors, added_chunks; - - if (!bdrv_get_dirty(source, s->dirty_bitmap, next_sector) || - test_bit(next_chunk, s->in_flight_bitmap)) { - assert(nb_sectors > 0); - break; - } - - added_sectors = sectors_per_chunk; - if (s->cow_bitmap && !test_bit(next_chunk, s->cow_bitmap)) { - bdrv_round_to_clusters(s->target, - next_sector, added_sectors, - &next_sector, &added_sectors); - - /* On the first iteration, the rounding may make us copy - * sectors before the first dirty one. - */ - if (next_sector < sector_num) { - assert(nb_sectors == 0); - sector_num = next_sector; - next_chunk = next_sector / sectors_per_chunk; - } - } - - added_sectors = MIN(added_sectors, end - (sector_num + nb_sectors)); - added_chunks = (added_sectors + sectors_per_chunk - 1) / sectors_per_chunk; - - /* When doing COW, it may happen that there is not enough space for - * a full cluster. Wait if that is the case. - */ - while (nb_chunks == 0 && s->buf_free_count < added_chunks) { - trace_mirror_yield_buf_busy(s, nb_chunks, s->in_flight); - s->waiting_for_io = true; - qemu_coroutine_yield(); - s->waiting_for_io = false; - } - if (s->buf_free_count < nb_chunks + added_chunks) { - trace_mirror_break_buf_busy(s, nb_chunks, s->in_flight); - break; - } - if (max_iov < nb_chunks + added_chunks) { - trace_mirror_break_iov_max(s, nb_chunks, added_chunks); - break; - } - - /* We have enough free space to copy these sectors. */ - bitmap_set(s->in_flight_bitmap, next_chunk, added_chunks); - - nb_sectors += added_sectors; - nb_chunks += added_chunks; - next_sector += added_sectors; - next_chunk += added_chunks; - if (!s->synced && s->common.speed) { - delay_ns = ratelimit_calculate_delay(&s->limit, added_sectors); - } - } while (delay_ns == 0 && next_sector < end); - /* Allocate a MirrorOp that is used as an AIO callback. */ op = g_new(MirrorOp, 1); op->s = s; @@ -279,47 +243,153 @@ static uint64_t coroutine_fn mirror_iteration(MirrorBlockJob *s) * from s->buf_free. */ qemu_iovec_init(&op->qiov, nb_chunks); - next_sector = sector_num; while (nb_chunks-- > 0) { MirrorBuffer *buf = QSIMPLEQ_FIRST(&s->buf_free); - size_t remaining = (nb_sectors * BDRV_SECTOR_SIZE) - op->qiov.size; + size_t remaining = nb_sectors * BDRV_SECTOR_SIZE - op->qiov.size; QSIMPLEQ_REMOVE_HEAD(&s->buf_free, next); s->buf_free_count--; qemu_iovec_add(&op->qiov, buf, MIN(s->granularity, remaining)); - - /* Advance the HBitmapIter in parallel, so that we do not examine - * the same sector twice. - */ - if (next_sector > hbitmap_next_sector - && bdrv_get_dirty(source, s->dirty_bitmap, next_sector)) { - hbitmap_next_sector = hbitmap_iter_next(&s->hbi); - } - - next_sector += sectors_per_chunk; } - bdrv_reset_dirty_bitmap(s->dirty_bitmap, sector_num, nb_sectors); - /* Copy the dirty cluster. */ s->in_flight++; s->sectors_in_flight += nb_sectors; trace_mirror_one_iteration(s, sector_num, nb_sectors); - ret = bdrv_get_block_status_above(source, NULL, sector_num, - nb_sectors, &pnum, &file); - if (ret < 0 || pnum < nb_sectors || - (ret & BDRV_BLOCK_DATA && !(ret & BDRV_BLOCK_ZERO))) { - bdrv_aio_readv(source, sector_num, &op->qiov, nb_sectors, - mirror_read_complete, op); - } else if (ret & BDRV_BLOCK_ZERO) { + bdrv_aio_readv(source, sector_num, &op->qiov, nb_sectors, + mirror_read_complete, op); + return ret; +} + +static void mirror_do_zero_or_discard(MirrorBlockJob *s, + int64_t sector_num, + int nb_sectors, + bool is_discard) +{ + MirrorOp *op; + + /* Allocate a MirrorOp that is used as an AIO callback. The qiov is zeroed + * so the freeing in mirror_iteration_done is nop. */ + op = g_new0(MirrorOp, 1); + op->s = s; + op->sector_num = sector_num; + op->nb_sectors = nb_sectors; + + s->in_flight++; + s->sectors_in_flight += nb_sectors; + if (is_discard) { + bdrv_aio_discard(s->target, sector_num, op->nb_sectors, + mirror_write_complete, op); + } else { bdrv_aio_write_zeroes(s->target, sector_num, op->nb_sectors, s->unmap ? BDRV_REQ_MAY_UNMAP : 0, mirror_write_complete, op); - } else { - assert(!(ret & BDRV_BLOCK_DATA)); - bdrv_aio_discard(s->target, sector_num, op->nb_sectors, - mirror_write_complete, op); + } +} + +static uint64_t coroutine_fn mirror_iteration(MirrorBlockJob *s) +{ + BlockDriverState *source = s->common.bs; + int64_t sector_num; + uint64_t delay_ns = 0; + /* At least the first dirty chunk is mirrored in one iteration. */ + int nb_chunks = 1; + int64_t end = s->bdev_length / BDRV_SECTOR_SIZE; + int sectors_per_chunk = s->granularity >> BDRV_SECTOR_BITS; + + sector_num = hbitmap_iter_next(&s->hbi); + if (sector_num < 0) { + bdrv_dirty_iter_init(s->dirty_bitmap, &s->hbi); + sector_num = hbitmap_iter_next(&s->hbi); + trace_mirror_restart_iter(s, bdrv_get_dirty_count(s->dirty_bitmap)); + assert(sector_num >= 0); + } + + /* 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)) { + int64_t hbitmap_next; + int64_t next_sector = sector_num + nb_chunks * sectors_per_chunk; + int64_t next_chunk = next_sector / sectors_per_chunk; + if (next_sector >= end || + !bdrv_get_dirty(source, s->dirty_bitmap, next_sector)) { + 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); + s->waiting_for_io = true; + qemu_coroutine_yield(); + s->waiting_for_io = false; + /* Now retry. */ + } else { + hbitmap_next = hbitmap_iter_next(&s->hbi); + assert(hbitmap_next == next_sector); + nb_chunks++; + } + } + + /* Clear dirty bits before querying the block status, because + * calling bdrv_get_block_status_above could yield - if some blocks are + * marked dirty in this window, we need to know. + */ + bdrv_reset_dirty_bitmap(s->dirty_bitmap, sector_num, + nb_chunks * sectors_per_chunk); + bitmap_set(s->in_flight_bitmap, sector_num / sectors_per_chunk, nb_chunks); + while (nb_chunks > 0 && sector_num < end) { + int ret; + int io_sectors; + BlockDriverState *file; + enum MirrorMethod { + MIRROR_METHOD_COPY, + MIRROR_METHOD_ZERO, + MIRROR_METHOD_DISCARD + } mirror_method = MIRROR_METHOD_COPY; + + assert(!(sector_num % sectors_per_chunk)); + ret = bdrv_get_block_status_above(source, NULL, sector_num, + nb_chunks * sectors_per_chunk, + &io_sectors, &file); + if (ret < 0) { + io_sectors = nb_chunks * sectors_per_chunk; + } + + io_sectors -= io_sectors % sectors_per_chunk; + if (io_sectors < sectors_per_chunk) { + io_sectors = sectors_per_chunk; + } else if (ret >= 0 && !(ret & BDRV_BLOCK_DATA)) { + int64_t target_sector_num; + int target_nb_sectors; + bdrv_round_to_clusters(s->target, sector_num, io_sectors, + &target_sector_num, &target_nb_sectors); + if (target_sector_num == sector_num && + target_nb_sectors == io_sectors) { + mirror_method = ret & BDRV_BLOCK_ZERO ? + MIRROR_METHOD_ZERO : + MIRROR_METHOD_DISCARD; + } + } + + switch (mirror_method) { + case MIRROR_METHOD_COPY: + io_sectors = mirror_do_read(s, sector_num, io_sectors); + break; + case MIRROR_METHOD_ZERO: + mirror_do_zero_or_discard(s, sector_num, io_sectors, false); + break; + case MIRROR_METHOD_DISCARD: + mirror_do_zero_or_discard(s, sector_num, io_sectors, true); + break; + default: + abort(); + } + assert(io_sectors); + sector_num += io_sectors; + nb_chunks -= io_sectors / sectors_per_chunk; + delay_ns += ratelimit_calculate_delay(&s->limit, io_sectors); } return delay_ns; } @@ -420,6 +490,7 @@ static void coroutine_fn mirror_run(void *opaque) checking for a NULL string */ int ret = 0; int n; + int target_cluster_size = BDRV_SECTOR_SIZE; if (block_job_is_cancelled(&s->common)) { goto immediate_exit; @@ -449,16 +520,16 @@ static void coroutine_fn mirror_run(void *opaque) */ bdrv_get_backing_filename(s->target, backing_filename, sizeof(backing_filename)); - if (backing_filename[0] && !s->target->backing) { - ret = bdrv_get_info(s->target, &bdi); - if (ret < 0) { - goto immediate_exit; - } - if (s->granularity < bdi.cluster_size) { - s->buf_size = MAX(s->buf_size, bdi.cluster_size); - s->cow_bitmap = bitmap_new(length); - } + if (!bdrv_get_info(s->target, &bdi) && bdi.cluster_size) { + target_cluster_size = bdi.cluster_size; + } + if (backing_filename[0] && !s->target->backing + && s->granularity < target_cluster_size) { + s->buf_size = MAX(s->buf_size, target_cluster_size); + s->cow_bitmap = bitmap_new(length); } + s->target_cluster_sectors = target_cluster_size >> BDRV_SECTOR_BITS; + s->max_iov = MIN(s->common.bs->bl.max_iov, s->target->bl.max_iov); end = s->bdev_length / BDRV_SECTOR_SIZE; s->buf = qemu_try_blockalign(bs, s->buf_size); -- cgit v1.1