Am 12.11.2013 um 16:49 schrieb Paolo Bonzini <pbonz...@redhat.com>:
> Writing zeroes to a file can be done by punching a hole if MAY_UNMAP
> is set.
>
> Note that in this case handle_aiocb_discard's ENOTSUP return code
> is not ignored, but makes the block layer fall back to the generic
> implementation.
>
> Signed-off-by: Paolo Bonzini <pbonz...@redhat.com>
> ---
> block/raw-posix.c | 64 ++++++++++++++++++++++++++++++++++++++++++++++++++++++-
> trace-events | 1 +
> 2 files changed, 64 insertions(+), 1 deletion(-)
>
> diff --git a/block/raw-posix.c b/block/raw-posix.c
> index 27fe47d..830e109 100644
> --- a/block/raw-posix.c
> +++ b/block/raw-posix.c
> @@ -142,6 +142,7 @@ typedef struct BDRVRawState {
> bool is_xfs : 1;
> #endif
> bool has_discard : 1;
> + bool discard_zeroes : 1;
> } BDRVRawState;
>
> typedef struct BDRVRawReopenState {
> @@ -283,6 +284,7 @@ static int raw_open_common(BlockDriverState *bs, QDict
> *options,
> Error *local_err = NULL;
> const char *filename;
> int fd, ret;
> + struct stat st;
>
> opts = qemu_opts_create_nofail(&raw_runtime_opts);
> qemu_opts_absorb_qdict(opts, options, &local_err);
> @@ -325,6 +327,15 @@ static int raw_open_common(BlockDriverState *bs, QDict
> *options,
> #endif
>
> s->has_discard = true;
> +
> + if (fstat(s->fd, &st) < 0) {
> + error_setg_errno(errp, errno, "Could not stat file");
> + goto fail;
> + }
> + if (S_ISREG(st.st_mode)) {
> + s->discard_zeroes = true;
> + }
> +
> #ifdef CONFIG_XFS
> if (platform_test_xfs_fd(s->fd)) {
> s->is_xfs = true;
> @@ -788,6 +799,29 @@ static int aio_worker(void *arg)
> return ret;
> }
>
> +static int paio_submit_co(BlockDriverState *bs, int fd,
> + int64_t sector_num, QEMUIOVector *qiov, int nb_sectors,
> + int type)
> +{
> + RawPosixAIOData *acb = g_slice_new(RawPosixAIOData);
> + ThreadPool *pool;
> +
> + acb->bs = bs;
> + acb->aio_type = type;
> + acb->aio_fildes = fd;
> +
> + if (qiov) {
> + acb->aio_iov = qiov->iov;
> + acb->aio_niov = qiov->niov;
> + }
> + acb->aio_nbytes = nb_sectors * 512;
> + acb->aio_offset = sector_num * 512;
> +
> + trace_paio_submit_co(sector_num, nb_sectors, type);
> + pool = aio_get_thread_pool(bdrv_get_aio_context(bs));
> + return thread_pool_submit_co(pool, aio_worker, acb);
> +}
> +
> static BlockDriverAIOCB *paio_submit(BlockDriverState *bs, int fd,
> int64_t sector_num, QEMUIOVector *qiov, int nb_sectors,
> BlockDriverCompletionFunc *cb, void *opaque, int type)
> @@ -1200,6 +1234,31 @@ static coroutine_fn BlockDriverAIOCB
> *raw_aio_discard(BlockDriverState *bs,
> cb, opaque, QEMU_AIO_DISCARD);
> }
>
> +static int coroutine_fn raw_co_write_zeroes(
> + BlockDriverState *bs, int64_t sector_num,
> + int nb_sectors, BdrvRequestFlags flags)
> +{
> + BDRVRawState *s = bs->opaque;
> +
> + if (!(flags & BDRV_REQ_MAY_UNMAP)) {
> + return -ENOTSUP;
> + }
> + if (!s->discard_zeroes) {
> + return -ENOTSUP;
> + }
> + return paio_submit_co(bs, s->fd, sector_num, NULL, nb_sectors,
> + QEMU_AIO_DISCARD);
> +}
> +
> +static int raw_get_info(BlockDriverState *bs, BlockDriverInfo *bdi)
> +{
> + BDRVRawState *s = bs->opaque;
> +
> + bdi->unallocated_blocks_are_zero = s->discard_zeroes;
> + bdi->can_write_zeroes_with_unmap = s->discard_zeroes;
does BLKDISCARDZEROES ioctl guarantee that a device is
zero initialized or does it just guarantee that a discard may not
fail and that it reads as zeroes afterwards?
Peter
> + return 0;
> +}
> +
> static QEMUOptionParameter raw_create_options[] = {
> {
> .name = BLOCK_OPT_SIZE,
> @@ -1223,6 +1282,7 @@ static BlockDriver bdrv_file = {
> .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_write_zeroes = raw_co_write_zeroes,
>
> .bdrv_aio_readv = raw_aio_readv,
> .bdrv_aio_writev = raw_aio_writev,
> @@ -1231,6 +1291,7 @@ static BlockDriver bdrv_file = {
>
> .bdrv_truncate = raw_truncate,
> .bdrv_getlength = raw_getlength,
> + .bdrv_get_info = raw_get_info,
> .bdrv_get_allocated_file_size
> = raw_get_allocated_file_size,
>
> @@ -1586,6 +1647,7 @@ static BlockDriver bdrv_host_device = {
>
> .bdrv_truncate = raw_truncate,
> .bdrv_getlength = raw_getlength,
> + .bdrv_get_info = raw_get_info,
> .bdrv_get_allocated_file_size
> = raw_get_allocated_file_size,
>
> @@ -1715,7 +1777,7 @@ static BlockDriver bdrv_host_floppy = {
> .bdrv_aio_flush = raw_aio_flush,
>
> .bdrv_truncate = raw_truncate,
> - .bdrv_getlength = raw_getlength,
> + .bdrv_getlength = raw_getlength,
> .has_variable_length = true,
> .bdrv_get_allocated_file_size
> = raw_get_allocated_file_size,
> diff --git a/trace-events b/trace-events
> index 96b3974..995c84a 100644
> --- a/trace-events
> +++ b/trace-events
> @@ -128,6 +128,7 @@ thread_pool_cancel(void *req, void *opaque) "req %p
> opaque %p"
>
> # block/raw-win32.c
> # block/raw-posix.c
> +paio_submit_co(int64_t sector_num, int nb_sectors, int type) "sector_num
> %"PRId64" nb_sectors %d type %d"
> paio_submit(void *acb, void *opaque, int64_t sector_num, int nb_sectors, int
> type) "acb %p opaque %p sector_num %"PRId64" nb_sectors %d type %d"
>
> # ioport.c
> --
> 1.8.4.2
>
>
