Re: [PATCH v2 4/7] block/block-copy: refactor interfaces to use bytes instead of end

[Vladimir Sementsov-Ogievskiy]

29.01.2020 20:12, Andrey Shinkevich wrote:
> 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.

No difference, if end == s->len, and end is aligned, then len is aligned too and "end == 
QEMU_ALIGN_UP(s->len, s->cluster_size)" is true. But "<=" looks more native for end and 
file len.

> 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>


--
Best regards,
Vladimir