From b3241e9274ca1aafb94ad8683305bb383e11c766 Mon Sep 17 00:00:00 2001 From: Eric Blake Date: Tue, 24 Apr 2018 14:25:03 -0500 Subject: [PATCH] null: Switch to byte-based read/write We are gradually moving away from sector-based interfaces, towards byte-based. Make the change for the last few sector-based callbacks in the null-co and null-aio drivers. Note that since the null driver does nothing on writes, it trivially supports the BDRV_REQ_FUA flag (all writes have already landed to the same bit-bucket without needing an extra flush call). Also, since the null driver does just as well with byte-based requests, we can now avoid cycles wasted on read-modify-write by taking advantage of the block layer now defaulting the alignment to 1 instead of 512. Signed-off-by: Eric Blake Signed-off-by: Kevin Wolf --- block/null.c | 45 +++++++++++++++++++++++---------------------- 1 file changed, 23 insertions(+), 22 deletions(-) diff --git a/block/null.c b/block/null.c index 3944550f67..5d610fdfba 100644 --- a/block/null.c +++ b/block/null.c @@ -93,6 +93,7 @@ static int null_file_open(BlockDriverState *bs, QDict *options, int flags, } s->read_zeroes = qemu_opt_get_bool(opts, NULL_OPT_ZEROES, false); qemu_opts_del(opts); + bs->supported_write_flags = BDRV_REQ_FUA; return ret; } @@ -116,22 +117,22 @@ static coroutine_fn int null_co_common(BlockDriverState *bs) return 0; } -static coroutine_fn int null_co_readv(BlockDriverState *bs, - int64_t sector_num, int nb_sectors, - QEMUIOVector *qiov) +static coroutine_fn int null_co_preadv(BlockDriverState *bs, + uint64_t offset, uint64_t bytes, + QEMUIOVector *qiov, int flags) { BDRVNullState *s = bs->opaque; if (s->read_zeroes) { - qemu_iovec_memset(qiov, 0, 0, nb_sectors * BDRV_SECTOR_SIZE); + qemu_iovec_memset(qiov, 0, 0, bytes); } return null_co_common(bs); } -static coroutine_fn int null_co_writev(BlockDriverState *bs, - int64_t sector_num, int nb_sectors, - QEMUIOVector *qiov) +static coroutine_fn int null_co_pwritev(BlockDriverState *bs, + uint64_t offset, uint64_t bytes, + QEMUIOVector *qiov, int flags) { return null_co_common(bs); } @@ -186,26 +187,26 @@ static inline BlockAIOCB *null_aio_common(BlockDriverState *bs, return &acb->common; } -static BlockAIOCB *null_aio_readv(BlockDriverState *bs, - int64_t sector_num, QEMUIOVector *qiov, - int nb_sectors, - BlockCompletionFunc *cb, - void *opaque) +static BlockAIOCB *null_aio_preadv(BlockDriverState *bs, + uint64_t offset, uint64_t bytes, + QEMUIOVector *qiov, int flags, + BlockCompletionFunc *cb, + void *opaque) { BDRVNullState *s = bs->opaque; if (s->read_zeroes) { - qemu_iovec_memset(qiov, 0, 0, nb_sectors * BDRV_SECTOR_SIZE); + qemu_iovec_memset(qiov, 0, 0, bytes); } return null_aio_common(bs, cb, opaque); } -static BlockAIOCB *null_aio_writev(BlockDriverState *bs, - int64_t sector_num, QEMUIOVector *qiov, - int nb_sectors, - BlockCompletionFunc *cb, - void *opaque) +static BlockAIOCB *null_aio_pwritev(BlockDriverState *bs, + uint64_t offset, uint64_t bytes, + QEMUIOVector *qiov, int flags, + BlockCompletionFunc *cb, + void *opaque) { return null_aio_common(bs, cb, opaque); } @@ -265,8 +266,8 @@ static BlockDriver bdrv_null_co = { .bdrv_close = null_close, .bdrv_getlength = null_getlength, - .bdrv_co_readv = null_co_readv, - .bdrv_co_writev = null_co_writev, + .bdrv_co_preadv = null_co_preadv, + .bdrv_co_pwritev = null_co_pwritev, .bdrv_co_flush_to_disk = null_co_flush, .bdrv_reopen_prepare = null_reopen_prepare, @@ -285,8 +286,8 @@ static BlockDriver bdrv_null_aio = { .bdrv_close = null_close, .bdrv_getlength = null_getlength, - .bdrv_aio_readv = null_aio_readv, - .bdrv_aio_writev = null_aio_writev, + .bdrv_aio_preadv = null_aio_preadv, + .bdrv_aio_pwritev = null_aio_pwritev, .bdrv_aio_flush = null_aio_flush, .bdrv_reopen_prepare = null_reopen_prepare, -- GitLab