diff options
| -rw-r--r-- | block.c | 65 |
1 files changed, 49 insertions, 16 deletions
@@ -2711,32 +2711,65 @@ int coroutine_fn bdrv_co_copy_on_readv(BlockDriverState *bs, BDRV_REQ_COPY_ON_READ); } +/* if no limit is specified in the BlockLimits use a default + * of 32768 512-byte sectors (16 MiB) per request. + */ +#define MAX_WRITE_ZEROES_DEFAULT 32768 + static int coroutine_fn bdrv_co_do_write_zeroes(BlockDriverState *bs, int64_t sector_num, int nb_sectors, BdrvRequestFlags flags) { BlockDriver *drv = bs->drv; QEMUIOVector qiov; - struct iovec iov; - int ret; + struct iovec iov = {0}; + int ret = 0; - /* TODO Emulate only part of misaligned requests instead of letting block - * drivers return -ENOTSUP and emulate everything */ + int max_write_zeroes = bs->bl.max_write_zeroes ? + bs->bl.max_write_zeroes : MAX_WRITE_ZEROES_DEFAULT; - /* First try the efficient write zeroes operation */ - if (drv->bdrv_co_write_zeroes) { - ret = drv->bdrv_co_write_zeroes(bs, sector_num, nb_sectors, flags); - if (ret != -ENOTSUP) { - return ret; + while (nb_sectors > 0 && !ret) { + int num = nb_sectors; + + /* align request */ + if (bs->bl.write_zeroes_alignment && + num >= bs->bl.write_zeroes_alignment && + sector_num % bs->bl.write_zeroes_alignment) { + if (num > bs->bl.write_zeroes_alignment) { + num = bs->bl.write_zeroes_alignment; + } + num -= sector_num % bs->bl.write_zeroes_alignment; } - } - /* Fall back to bounce buffer if write zeroes is unsupported */ - iov.iov_len = nb_sectors * BDRV_SECTOR_SIZE; - iov.iov_base = qemu_blockalign(bs, iov.iov_len); - memset(iov.iov_base, 0, iov.iov_len); - qemu_iovec_init_external(&qiov, &iov, 1); + /* limit request size */ + if (num > max_write_zeroes) { + num = max_write_zeroes; + } + + ret = -ENOTSUP; + /* First try the efficient write zeroes operation */ + if (drv->bdrv_co_write_zeroes) { + ret = drv->bdrv_co_write_zeroes(bs, sector_num, num, flags); + } + + if (ret == -ENOTSUP) { + /* Fall back to bounce buffer if write zeroes is unsupported */ + iov.iov_len = num * BDRV_SECTOR_SIZE; + if (iov.iov_base == NULL) { + /* allocate bounce buffer only once and ensure that it + * is big enough for this and all future requests. + */ + size_t bufsize = num <= nb_sectors ? num : max_write_zeroes; + iov.iov_base = qemu_blockalign(bs, bufsize * BDRV_SECTOR_SIZE); + memset(iov.iov_base, 0, bufsize * BDRV_SECTOR_SIZE); + } + qemu_iovec_init_external(&qiov, &iov, 1); - ret = drv->bdrv_co_writev(bs, sector_num, nb_sectors, &qiov); + ret = drv->bdrv_co_writev(bs, sector_num, num, &qiov); + } + + sector_num += num; + nb_sectors -= num; + } qemu_vfree(iov.iov_base); return ret; |