Re: [Qemu-devel] [PATCH v2 14/24] block: Switch BdrvTrackedRequest to byte granularity

[Max Reitz <mreitz@redhat.com>]

On 13.12.2013 14:22, Kevin Wolf wrote:
> Signed-off-by: Kevin Wolf <kwolf@redhat.com>
> ---
>   block.c                   | 52 +++++++++++++++++++++++++++++++----------------
>   block/backup.c            |  7 ++++++-
>   include/block/block_int.h |  4 ++--
>   3 files changed, 42 insertions(+), 21 deletions(-)
>
> diff --git a/block.c b/block.c
> index a80db2e..fa888d9 100644
> --- a/block.c
> +++ b/block.c
> @@ -2037,13 +2037,13 @@ static void tracked_request_end(BdrvTrackedRequest *req)
>    */
>   static void tracked_request_begin(BdrvTrackedRequest *req,
>                                     BlockDriverState *bs,
> -                                  int64_t sector_num,
> -                                  int nb_sectors, bool is_write)
> +                                  int64_t offset,
> +                                  unsigned int bytes, bool is_write)
>   {
>       *req = (BdrvTrackedRequest){
>           .bs = bs,
> -        .sector_num = sector_num,
> -        .nb_sectors = nb_sectors,
> +        .offset = offset,
> +        .bytes = bytes,
>           .is_write = is_write,
>           .co = qemu_coroutine_self(),
>       };
> @@ -2074,25 +2074,43 @@ void bdrv_round_to_clusters(BlockDriverState *bs,
>       }
>   }
>   
> +static void round_bytes_to_clusters(BlockDriverState *bs,
> +                                    int64_t offset, unsigned int bytes,
> +                                    int64_t *cluster_offset,
> +                                    unsigned int *cluster_bytes)
> +{
> +    BlockDriverInfo bdi;
> +
> +    if (bdrv_get_info(bs, &bdi) < 0 || bdi.cluster_size == 0) {
> +        *cluster_offset = offset;
> +        *cluster_bytes = bytes;
> +    } else {
> +        *cluster_offset = QEMU_ALIGN_DOWN(offset, bdi.cluster_size);
> +        *cluster_bytes = QEMU_ALIGN_UP(offset - *cluster_offset + bytes,
> +                                       bdi.cluster_size);
> +    }
> +}
> +
>   static bool tracked_request_overlaps(BdrvTrackedRequest *req,
> -                                     int64_t sector_num, int nb_sectors) {
> +                                     int64_t offset, int bytes)

Shouldn't this be "unsigned int bytes"?

Max

> +{
>       /*        aaaa   bbbb */
> -    if (sector_num >= req->sector_num + req->nb_sectors) {
> +    if (offset >= req->offset + req->bytes) {
>           return false;
>       }
>       /* bbbb   aaaa        */
> -    if (req->sector_num >= sector_num + nb_sectors) {
> +    if (req->offset >= offset + bytes) {
>           return false;
>       }
>       return true;
>   }
>   
>   static void coroutine_fn wait_for_overlapping_requests(BlockDriverState *bs,
> -        int64_t sector_num, int nb_sectors)
> +        int64_t offset, unsigned int bytes)
>   {
>       BdrvTrackedRequest *req;
> -    int64_t cluster_sector_num;
> -    int cluster_nb_sectors;
> +    int64_t cluster_offset;
> +    unsigned int cluster_bytes;
>       bool retry;
>   
>       /* If we touch the same cluster it counts as an overlap.  This guarantees
> @@ -2101,14 +2119,12 @@ static void coroutine_fn wait_for_overlapping_requests(BlockDriverState *bs,
>        * CoR read and write operations are atomic and guest writes cannot
>        * interleave between them.
>        */
> -    bdrv_round_to_clusters(bs, sector_num, nb_sectors,
> -                           &cluster_sector_num, &cluster_nb_sectors);
> +    round_bytes_to_clusters(bs, offset, bytes, &cluster_offset, &cluster_bytes);
>   
>       do {
>           retry = false;
>           QLIST_FOREACH(req, &bs->tracked_requests, list) {
> -            if (tracked_request_overlaps(req, cluster_sector_num,
> -                                         cluster_nb_sectors)) {
> +            if (tracked_request_overlaps(req, cluster_offset, cluster_bytes)) {
>                   /* Hitting this means there was a reentrant request, for
>                    * example, a block driver issuing nested requests.  This must
>                    * never happen since it means deadlock.
> @@ -2723,10 +2739,10 @@ static int coroutine_fn bdrv_aligned_preadv(BlockDriverState *bs,
>       }
>   
>       if (bs->copy_on_read_in_flight) {
> -        wait_for_overlapping_requests(bs, sector_num, nb_sectors);
> +        wait_for_overlapping_requests(bs, offset, bytes);
>       }
>   
> -    tracked_request_begin(&req, bs, sector_num, nb_sectors, false);
> +    tracked_request_begin(&req, bs, offset, bytes, false);
>   
>       if (flags & BDRV_REQ_COPY_ON_READ) {
>           int pnum;
> @@ -2974,10 +2990,10 @@ static int coroutine_fn bdrv_aligned_pwritev(BlockDriverState *bs,
>       assert((bytes & (BDRV_SECTOR_SIZE - 1)) == 0);
>   
>       if (bs->copy_on_read_in_flight) {
> -        wait_for_overlapping_requests(bs, sector_num, nb_sectors);
> +        wait_for_overlapping_requests(bs, offset, bytes);
>       }
>   
> -    tracked_request_begin(&req, bs, sector_num, nb_sectors, true);
> +    tracked_request_begin(&req, bs, offset, bytes, true);
>   
>       ret = notifier_with_return_list_notify(&bs->before_write_notifiers, &req);
>   
> diff --git a/block/backup.c b/block/backup.c
> index 0198514..15a2e55 100644
> --- a/block/backup.c
> +++ b/block/backup.c
> @@ -181,8 +181,13 @@ static int coroutine_fn backup_before_write_notify(
>           void *opaque)
>   {
>       BdrvTrackedRequest *req = opaque;
> +    int64_t sector_num = req->offset >> BDRV_SECTOR_BITS;
> +    int nb_sectors = req->bytes >> BDRV_SECTOR_BITS;
>   
> -    return backup_do_cow(req->bs, req->sector_num, req->nb_sectors, NULL);
> +    assert((req->offset & (BDRV_SECTOR_SIZE - 1)) == 0);
> +    assert((req->bytes & (BDRV_SECTOR_SIZE - 1)) == 0);
> +
> +    return backup_do_cow(req->bs, sector_num, nb_sectors, NULL);
>   }
>   
>   static void backup_set_speed(BlockJob *job, int64_t speed, Error **errp)
> diff --git a/include/block/block_int.h b/include/block/block_int.h
> index 0a01b69..a11e5c9 100644
> --- a/include/block/block_int.h
> +++ b/include/block/block_int.h
> @@ -57,8 +57,8 @@
>   
>   typedef struct BdrvTrackedRequest {
>       BlockDriverState *bs;
> -    int64_t sector_num;
> -    int nb_sectors;
> +    int64_t offset;
> +    unsigned int bytes;
>       bool is_write;
>       QLIST_ENTRY(BdrvTrackedRequest) list;
>       Coroutine *co; /* owner, used for deadlock detection */