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Re: [PATCH v2 4/7] block/block-copy: refactor interfaces to use bytes in
From: |
Andrey Shinkevich |
Subject: |
Re: [PATCH v2 4/7] block/block-copy: refactor interfaces to use bytes instead of end |
Date: |
Wed, 29 Jan 2020 17:12:25 +0000 |
On 27/11/2019 21:08, Vladimir Sementsov-Ogievskiy wrote:
> We have a lot of "chunk_end - start" invocations, let's switch to
> bytes/cur_bytes scheme instead.
>
> Signed-off-by: Vladimir Sementsov-Ogievskiy <address@hidden>
> ---
> include/block/block-copy.h | 4 +--
> block/block-copy.c | 68 ++++++++++++++++++++------------------
> 2 files changed, 37 insertions(+), 35 deletions(-)
>
> diff --git a/include/block/block-copy.h b/include/block/block-copy.h
> index 0a161724d7..7321b3d305 100644
> --- a/include/block/block-copy.h
> +++ b/include/block/block-copy.h
> @@ -19,8 +19,8 @@
> #include "qemu/co-shared-resource.h"
>
> typedef struct BlockCopyInFlightReq {
> - int64_t start_byte;
> - int64_t end_byte;
> + int64_t start;
> + int64_t bytes;
> QLIST_ENTRY(BlockCopyInFlightReq) list;
> CoQueue wait_queue; /* coroutines blocked on this request */
> } BlockCopyInFlightReq;
> diff --git a/block/block-copy.c b/block/block-copy.c
> index 94e7e855ef..cc273b6cb8 100644
> --- a/block/block-copy.c
> +++ b/block/block-copy.c
> @@ -26,12 +26,12 @@
>
> static BlockCopyInFlightReq *block_copy_find_inflight_req(BlockCopyState *s,
> int64_t start,
> - int64_t end)
> + int64_t bytes)
> {
> BlockCopyInFlightReq *req;
>
> QLIST_FOREACH(req, &s->inflight_reqs, list) {
> - if (end > req->start_byte && start < req->end_byte) {
> + if (start + bytes > req->start && start < req->start + req->bytes) {
> return req;
> }
> }
> @@ -41,21 +41,21 @@ static BlockCopyInFlightReq
> *block_copy_find_inflight_req(BlockCopyState *s,
>
> static void coroutine_fn block_copy_wait_inflight_reqs(BlockCopyState *s,
> int64_t start,
> - int64_t end)
> + int64_t bytes)
> {
> BlockCopyInFlightReq *req;
>
> - while ((req = block_copy_find_inflight_req(s, start, end))) {
> + while ((req = block_copy_find_inflight_req(s, start, bytes))) {
> qemu_co_queue_wait(&req->wait_queue, NULL);
> }
> }
>
> static void block_copy_inflight_req_begin(BlockCopyState *s,
> BlockCopyInFlightReq *req,
> - int64_t start, int64_t end)
> + int64_t start, int64_t bytes)
> {
> - req->start_byte = start;
> - req->end_byte = end;
> + req->start = start;
> + req->bytes = bytes;
> qemu_co_queue_init(&req->wait_queue);
> QLIST_INSERT_HEAD(&s->inflight_reqs, req, list);
> }
> @@ -150,24 +150,26 @@ void block_copy_set_callbacks(
> /*
> * block_copy_do_copy
> *
> - * Do copy of cluser-aligned chunk. @end is allowed to exceed s->len only to
> - * cover last cluster when s->len is not aligned to clusters.
> + * Do copy of cluser-aligned chunk. Requested region is allowed to exceed
> s->len
cluster-...
> + * only to cover last cluster when s->len is not aligned to clusters.
> *
> * No sync here: nor bitmap neighter intersecting requests handling, only
> copy.
> *
> * Returns 0 on success.
> */
> static int coroutine_fn block_copy_do_copy(BlockCopyState *s,
> - int64_t start, int64_t end,
> + int64_t start, int64_t bytes,
> bool zeroes, bool *error_is_read)
> {
> int ret;
> - int nbytes = MIN(end, s->len) - start;
> + int nbytes = MIN(start + bytes, s->len) - start;
> void *bounce_buffer = NULL;
>
> + assert(start >= 0 && bytes > 0 && INT64_MAX - start >= bytes);
> assert(QEMU_IS_ALIGNED(start, s->cluster_size));
> - assert(QEMU_IS_ALIGNED(end, s->cluster_size));
> - assert(end < s->len || end == QEMU_ALIGN_UP(s->len, s->cluster_size));
> + assert(QEMU_IS_ALIGNED(bytes, s->cluster_size));
> + assert(start + bytes <= s->len ||
The '<=' looks correct but I wonder how only '<' worked without
assertion failure before. Was the s->len never aligned to the cluster size?
> + start + bytes == QEMU_ALIGN_UP(s->len, s->cluster_size));
>
> if (zeroes) {
> ret = bdrv_co_pwrite_zeroes(s->target, start, nbytes,
> s->write_flags &
> @@ -347,7 +349,6 @@ int coroutine_fn block_copy(BlockCopyState *s,
> bool *error_is_read)
> {
> int ret = 0;
> - int64_t end = bytes + start; /* bytes */
> BlockCopyInFlightReq req;
>
> /*
> @@ -358,58 +359,59 @@ int coroutine_fn block_copy(BlockCopyState *s,
> bdrv_get_aio_context(s->target->bs));
>
> assert(QEMU_IS_ALIGNED(start, s->cluster_size));
> - assert(QEMU_IS_ALIGNED(end, s->cluster_size));
> + assert(QEMU_IS_ALIGNED(bytes, s->cluster_size));
>
> block_copy_wait_inflight_reqs(s, start, bytes);
> - block_copy_inflight_req_begin(s, &req, start, end);
> + block_copy_inflight_req_begin(s, &req, start, bytes);
>
> - while (start < end) {
> - int64_t next_zero, chunk_end, status_bytes;
> + while (bytes) {
> + int64_t next_zero, cur_bytes, status_bytes;
>
> if (!bdrv_dirty_bitmap_get(s->copy_bitmap, start)) {
> trace_block_copy_skip(s, start);
> start += s->cluster_size;
> + bytes -= s->cluster_size;
> continue; /* already copied */
> }
>
> - chunk_end = MIN(end, start + s->copy_size);
> + cur_bytes = MIN(bytes, s->copy_size);
>
> next_zero = bdrv_dirty_bitmap_next_zero(s->copy_bitmap, start,
> - chunk_end - start);
> + cur_bytes);
> if (next_zero >= 0) {
> assert(next_zero > start); /* start is dirty */
> - assert(next_zero < chunk_end); /* no need to do MIN() */
> - chunk_end = next_zero;
> + assert(next_zero < start + cur_bytes); /* no need to do MIN() */
> + cur_bytes = next_zero - start;
> }
>
> - ret = block_copy_block_status(s, start, chunk_end - start,
> - &status_bytes);
> + ret = block_copy_block_status(s, start, cur_bytes, &status_bytes);
> if (s->skip_unallocated && !(ret & BDRV_BLOCK_ALLOCATED)) {
> bdrv_reset_dirty_bitmap(s->copy_bitmap, start, status_bytes);
> s->progress_reset_callback(s->progress_opaque);
> trace_block_copy_skip_range(s, start, status_bytes);
> start += status_bytes;
> + bytes -= status_bytes;
> continue;
> }
>
> - chunk_end = MIN(chunk_end, start + status_bytes);
> + cur_bytes = MIN(cur_bytes, status_bytes);
>
> trace_block_copy_process(s, start);
>
> - bdrv_reset_dirty_bitmap(s->copy_bitmap, start, chunk_end - start);
> + bdrv_reset_dirty_bitmap(s->copy_bitmap, start, cur_bytes);
>
> - co_get_from_shres(s->mem, chunk_end - start);
> - ret = block_copy_do_copy(s, start, chunk_end, ret & BDRV_BLOCK_ZERO,
> + co_get_from_shres(s->mem, cur_bytes);
> + ret = block_copy_do_copy(s, start, cur_bytes, ret & BDRV_BLOCK_ZERO,
> error_is_read);
> - co_put_to_shres(s->mem, chunk_end - start);
> + co_put_to_shres(s->mem, cur_bytes);
> if (ret < 0) {
> - bdrv_set_dirty_bitmap(s->copy_bitmap, start, chunk_end - start);
> + bdrv_set_dirty_bitmap(s->copy_bitmap, start, cur_bytes);
> break;
> }
>
> - s->progress_bytes_callback(chunk_end - start, s->progress_opaque);
> - start = chunk_end;
> - ret = 0;
> + s->progress_bytes_callback(cur_bytes, s->progress_opaque);
> + start += cur_bytes;
> + bytes -= cur_bytes;
> }
>
> block_copy_inflight_req_end(&req);
>
At the first glance, we would only benefit from the 'while' loop by that
substitution to reduce the number of addition operations.
Reviewed-by: Andrey Shinkevich <address@hidden>
--
With the best regards,
Andrey Shinkevich
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