Commit f06f6b66 authored by Eric Blake's avatar Eric Blake Committed by Kevin Wolf
Browse files

qcow2: Switch is_zero_sectors() to byte-based 



We are gradually converting to byte-based interfaces, as they are
easier to reason about than sector-based.  Convert another internal
function (no semantic change), and rename it to is_zero() in the
process.

Signed-off-by: default avatarEric Blake <eblake@redhat.com>
Reviewed-by: default avatarFam Zheng <famz@redhat.com>
Reviewed-by: default avatarJohn Snow <jsnow@redhat.com>
Signed-off-by: default avatarKevin Wolf <kwolf@redhat.com>
parent 7cfd5275

block/qcow2.c

+19 −14
Original line number Diff line number Diff line
@@ -2972,21 +2972,29 @@ finish: 
}





static bool is_zero_sectors(BlockDriverState *bs, int64_t start,

                            uint32_t count)

static bool is_zero(BlockDriverState *bs, int64_t offset, int64_t bytes)

{

    int nr;

    int64_t res;

    int64_t start;



    if (start + count > bs->total_sectors) {

        count = bs->total_sectors - start;

    /* TODO: Widening to sector boundaries should only be needed as

     * long as we can't query finer granularity. */

    start = QEMU_ALIGN_DOWN(offset, BDRV_SECTOR_SIZE);

    bytes = QEMU_ALIGN_UP(offset + bytes, BDRV_SECTOR_SIZE) - start;



    /* Clamp to image length, before checking status of underlying sectors */

    if (start + bytes > bs->total_sectors * BDRV_SECTOR_SIZE) {

        bytes = bs->total_sectors * BDRV_SECTOR_SIZE - start;

    }



    if (!count) {

    if (!bytes) {

        return true;

    }

    res = bdrv_get_block_status_above(bs, NULL, start, count, &nr, NULL);

    return res >= 0 && (res & BDRV_BLOCK_ZERO) && nr == count;

    res = bdrv_get_block_status_above(bs, NULL, start >> BDRV_SECTOR_BITS,

                                      bytes >> BDRV_SECTOR_BITS, &nr, NULL);

    return res >= 0 && (res & BDRV_BLOCK_ZERO) &&

        nr * BDRV_SECTOR_SIZE == bytes;

}



static coroutine_fn int qcow2_co_pwrite_zeroes(BlockDriverState *bs,
@@ -3004,24 +3012,21 @@ static coroutine_fn int qcow2_co_pwrite_zeroes(BlockDriverState *bs, 
    }



    if (head || tail) {

        int64_t cl_start = (offset - head) >> BDRV_SECTOR_BITS;

        uint64_t off;

        unsigned int nr;



        assert(head + bytes <= s->cluster_size);



        /* check whether remainder of cluster already reads as zero */

        if (!(is_zero_sectors(bs, cl_start,

                              DIV_ROUND_UP(head, BDRV_SECTOR_SIZE)) &&

              is_zero_sectors(bs, (offset + bytes) >> BDRV_SECTOR_BITS,

                              DIV_ROUND_UP(-tail & (s->cluster_size - 1),

                                           BDRV_SECTOR_SIZE)))) {

        if (!(is_zero(bs, offset - head, head) &&

              is_zero(bs, offset + bytes,

                      tail ? s->cluster_size - tail : 0))) {

            return -ENOTSUP;

        }



        qemu_co_mutex_lock(&s->lock);

        /* We can have new write after previous check */

        offset = cl_start << BDRV_SECTOR_BITS;

        offset = QEMU_ALIGN_DOWN(offset, s->cluster_size);

        bytes = s->cluster_size;

        nr = s->cluster_size;

        ret = qcow2_get_cluster_offset(bs, offset, &nr, &off);