On Thu, 09/14 09:40, Eric Blake wrote:
> We are gradually moving away from sector-based interfaces, towards
> byte-based. Update the file protocol driver accordingly. In mapping
> mode, note that the entire file is reported as allocated, so we can
> take a shortcut and skip lseek().
>
> Signed-off-by: Eric Blake <ebl...@redhat.com>
>
> ---
> v2: tweak comment, add mapping support
> ---
> block/file-posix.c | 57
> ++++++++++++++++++++++++++++++------------------------
> 1 file changed, 32 insertions(+), 25 deletions(-)
>
> diff --git a/block/file-posix.c b/block/file-posix.c
> index 72ecfbb0e0..6813059867 100644
> --- a/block/file-posix.c
> +++ b/block/file-posix.c
> @@ -2107,24 +2107,25 @@ static int find_allocation(BlockDriverState *bs,
> off_t start,
> }
>
> /*
> - * Returns the allocation status of the specified sectors.
> + * Returns the allocation status of the specified offset.
> *
> - * If 'sector_num' is beyond the end of the disk image the return value is 0
> + * If 'offset' is beyond the end of the disk image the return value is 0
> * and 'pnum' is set to 0.
> *
> - * 'pnum' is set to the number of sectors (including and immediately
> following
> - * the specified sector) that are known to be in the same
> + * 'pnum' is set to the number of bytes (including and immediately following
> + * the specified offset) that are known to be in the same
> * allocated/unallocated state.
> *
> - * 'nb_sectors' is the max value 'pnum' should be set to. If nb_sectors goes
> + * 'bytes' is the max value 'pnum' should be set to. If bytes goes
> * beyond the end of the disk image it will be clamped.
> */
> -static int64_t coroutine_fn raw_co_get_block_status(BlockDriverState *bs,
> - int64_t sector_num,
> - int nb_sectors, int
> *pnum,
> - BlockDriverState **file)
> +static int64_t coroutine_fn raw_co_block_status(BlockDriverState *bs,
> + bool mapping,
> + int64_t offset,
> + int64_t bytes, int64_t *pnum,
> + BlockDriverState **file)
> {
> - off_t start, data = 0, hole = 0;
> + off_t data = 0, hole = 0;
> int64_t total_size;
> int ret;
>
> @@ -2133,39 +2134,45 @@ static int64_t coroutine_fn
> raw_co_get_block_status(BlockDriverState *bs,
> return ret;
> }
>
> - start = sector_num * BDRV_SECTOR_SIZE;
> total_size = bdrv_getlength(bs);
> if (total_size < 0) {
> return total_size;
> - } else if (start >= total_size) {
> + } else if (offset >= total_size) {
> *pnum = 0;
> return 0;
> - } else if (start + nb_sectors * BDRV_SECTOR_SIZE > total_size) {
> - nb_sectors = DIV_ROUND_UP(total_size - start, BDRV_SECTOR_SIZE);
> + } else if (offset + bytes > total_size) {
> + bytes = total_size - offset;
> }
>
> - ret = find_allocation(bs, start, &data, &hole);
> + if (!mapping) {
> + *pnum = bytes;
> + *file = bs;
> + return BDRV_BLOCK_DATA | BDRV_BLOCK_OFFSET_VALID |
> + (offset & BDRV_BLOCK_OFFSET_MASK);
> + }
I may be missing something, because the last time I tried to understand the
rationale behind "mapping" was already some time ago: shouldn't we still
distinguish hole and data? What will omitting BDRV_BLOCK_ZERO help?
Fam
> +
> + ret = find_allocation(bs, offset, &data, &hole);
> if (ret == -ENXIO) {
> /* Trailing hole */
> - *pnum = nb_sectors;
> + *pnum = bytes;
> ret = BDRV_BLOCK_ZERO;
> } else if (ret < 0) {
> /* No info available, so pretend there are no holes */
> - *pnum = nb_sectors;
> + *pnum = bytes;
> ret = BDRV_BLOCK_DATA;
> - } else if (data == start) {
> - /* On a data extent, compute sectors to the end of the extent,
> + } else if (data == offset) {
> + /* On a data extent, compute bytes to the end of the extent,
> * possibly including a partial sector at EOF. */
> - *pnum = MIN(nb_sectors, DIV_ROUND_UP(hole - start,
> BDRV_SECTOR_SIZE));
> + *pnum = MIN(bytes, hole - offset);
> ret = BDRV_BLOCK_DATA;
> } else {
> - /* On a hole, compute sectors to the beginning of the next extent.
> */
> - assert(hole == start);
> - *pnum = MIN(nb_sectors, (data - start) / BDRV_SECTOR_SIZE);
> + /* On a hole, compute bytes to the beginning of the next extent. */
> + assert(hole == offset);
> + *pnum = MIN(bytes, data - offset);
> ret = BDRV_BLOCK_ZERO;
> }
> *file = bs;
> - return ret | BDRV_BLOCK_OFFSET_VALID | start;
> + return ret | BDRV_BLOCK_OFFSET_VALID | (offset & BDRV_BLOCK_OFFSET_MASK);
> }
>
> static coroutine_fn BlockAIOCB *raw_aio_pdiscard(BlockDriverState *bs,
> @@ -2259,7 +2266,7 @@ BlockDriver bdrv_file = {
> .bdrv_close = raw_close,
> .bdrv_create = raw_create,
> .bdrv_has_zero_init = bdrv_has_zero_init_1,
> - .bdrv_co_get_block_status = raw_co_get_block_status,
> + .bdrv_co_block_status = raw_co_block_status,
> .bdrv_co_pwrite_zeroes = raw_co_pwrite_zeroes,
>
> .bdrv_co_preadv = raw_co_preadv,
> --
> 2.13.5
>
