diff options
Diffstat (limited to 'block.c')
| -rw-r--r-- | block.c | 35 |
1 files changed, 23 insertions, 12 deletions
@@ -2771,14 +2771,21 @@ static int coroutine_fn bdrv_co_do_write_zeroes(BlockDriverState *bs, 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) { + /* Align request. Block drivers can expect the "bulk" of the request + * to be aligned. + */ + if (bs->bl.write_zeroes_alignment + && num > bs->bl.write_zeroes_alignment) { + if (sector_num % bs->bl.write_zeroes_alignment != 0) { + /* Make a small request up to the first aligned sector. */ num = bs->bl.write_zeroes_alignment; + num -= sector_num % bs->bl.write_zeroes_alignment; + } else if ((sector_num + num) % bs->bl.write_zeroes_alignment != 0) { + /* Shorten the request to the last aligned sector. num cannot + * underflow because num > bs->bl.write_zeroes_alignment. + */ + num -= (sector_num + num) % bs->bl.write_zeroes_alignment; } - num -= sector_num % bs->bl.write_zeroes_alignment; } /* limit request size */ @@ -2796,16 +2803,20 @@ static int coroutine_fn bdrv_co_do_write_zeroes(BlockDriverState *bs, /* 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); + iov.iov_base = qemu_blockalign(bs, num * BDRV_SECTOR_SIZE); + memset(iov.iov_base, 0, num * BDRV_SECTOR_SIZE); } qemu_iovec_init_external(&qiov, &iov, 1); ret = drv->bdrv_co_writev(bs, sector_num, num, &qiov); + + /* Keep bounce buffer around if it is big enough for all + * all future requests. + */ + if (num < max_write_zeroes) { + qemu_vfree(iov.iov_base); + iov.iov_base = NULL; + } } sector_num += num; |