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block: Support byte-based aio callbacks

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We are gradually moving away from sector-based interfaces, towards
byte-based.  Add new sector-based aio callbacks for read and write,
to match the fact that bdrv_aio_pdiscard is already byte-based.

Ideally, drivers should be converted to use coroutine callbacks
rather than aio; but that is not quite as trivial (and if we were
to do that conversion, the null-aio driver would disappear), so for
the short term, converting the signature but keeping things with
aio is easier.  However, we CAN declare that a driver that uses
the byte-based aio interfaces now defaults to byte-based
operations, and must explicitly provide a refresh_limits override
to stick with larger alignments (making the alignment issues more
obvious directly in the drivers touched in the next few patches).

Once all drivers are converted, the sector-based aio callbacks will
be removed; in the meantime, a FIXME comment is added due to a
slight inefficiency that will be touched up as part of that later
cleanup.

Simplify some instances of 'bs->drv' into 'drv' while touching this,
since the local variable already exists to reduce typing.

Signed-off-by: Eric Blake <eblake@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
This commit is contained in:
Eric Blake 2018-04-24 14:25:01 -05:00 committed by Kevin Wolf
parent 7803696d85
commit e31f6864a6
2 changed files with 35 additions and 9 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

38
block/io.c
View File

@ -92,7 +92,8 @@ void bdrv_refresh_limits(BlockDriverState *bs, Error **errp)
}
/* Default alignment based on whether driver has byte interface */
bs->bl.request_alignment = drv->bdrv_co_preadv ? 1 : 512;
bs->bl.request_alignment = (drv->bdrv_co_preadv ||
drv->bdrv_aio_preadv) ? 1 : 512;
/* Take some limits from the children as a default */
if (bs->file) {
@ -924,12 +925,15 @@ static int coroutine_fn bdrv_driver_preadv(BlockDriverState *bs,
return drv->bdrv_co_preadv(bs, offset, bytes, qiov, flags);
}
/* FIXME - no need to calculate these if .bdrv_aio_preadv exists */
sector_num = offset >> BDRV_SECTOR_BITS;
nb_sectors = bytes >> BDRV_SECTOR_BITS;
assert((offset & (BDRV_SECTOR_SIZE - 1)) == 0);
assert((bytes & (BDRV_SECTOR_SIZE - 1)) == 0);
assert((bytes >> BDRV_SECTOR_BITS) <= BDRV_REQUEST_MAX_SECTORS);
if (!drv->bdrv_aio_preadv) {
assert((offset & (BDRV_SECTOR_SIZE - 1)) == 0);
assert((bytes & (BDRV_SECTOR_SIZE - 1)) == 0);
assert((bytes >> BDRV_SECTOR_BITS) <= BDRV_REQUEST_MAX_SECTORS);
}
if (drv->bdrv_co_readv) {
return drv->bdrv_co_readv(bs, sector_num, nb_sectors, qiov);
@ -939,8 +943,13 @@ static int coroutine_fn bdrv_driver_preadv(BlockDriverState *bs,
.coroutine = qemu_coroutine_self(),
};
acb = bs->drv->bdrv_aio_readv(bs, sector_num, qiov, nb_sectors,
if (drv->bdrv_aio_preadv) {
acb = drv->bdrv_aio_preadv(bs, offset, bytes, qiov, flags,
bdrv_co_io_em_complete, &co);
} else {
acb = drv->bdrv_aio_readv(bs, sector_num, qiov, nb_sectors,
bdrv_co_io_em_complete, &co);
}
if (acb == NULL) {
return -EIO;
} else {
@ -972,12 +981,15 @@ static int coroutine_fn bdrv_driver_pwritev(BlockDriverState *bs,
goto emulate_flags;
}
/* FIXME - no need to calculate these if .bdrv_aio_pwritev exists */
sector_num = offset >> BDRV_SECTOR_BITS;
nb_sectors = bytes >> BDRV_SECTOR_BITS;
assert((offset & (BDRV_SECTOR_SIZE - 1)) == 0);
assert((bytes & (BDRV_SECTOR_SIZE - 1)) == 0);
assert((bytes >> BDRV_SECTOR_BITS) <= BDRV_REQUEST_MAX_SECTORS);
if (!drv->bdrv_aio_pwritev) {
assert((offset & (BDRV_SECTOR_SIZE - 1)) == 0);
assert((bytes & (BDRV_SECTOR_SIZE - 1)) == 0);
assert((bytes >> BDRV_SECTOR_BITS) <= BDRV_REQUEST_MAX_SECTORS);
}
if (drv->bdrv_co_writev_flags) {
ret = drv->bdrv_co_writev_flags(bs, sector_num, nb_sectors, qiov,
@ -992,8 +1004,16 @@ static int coroutine_fn bdrv_driver_pwritev(BlockDriverState *bs,
.coroutine = qemu_coroutine_self(),
};
acb = bs->drv->bdrv_aio_writev(bs, sector_num, qiov, nb_sectors,
if (drv->bdrv_aio_pwritev) {
acb = drv->bdrv_aio_pwritev(bs, offset, bytes, qiov,
flags & bs->supported_write_flags,
bdrv_co_io_em_complete, &co);
flags &= ~bs->supported_write_flags;
} else {
assert(!bs->supported_write_flags);
acb = drv->bdrv_aio_writev(bs, sector_num, qiov, nb_sectors,
bdrv_co_io_em_complete, &co);
}
if (acb == NULL) {
ret = -EIO;
} else {

6
include/block/block_int.h
View File

@ -144,9 +144,15 @@ struct BlockDriver {
BlockAIOCB *(*bdrv_aio_readv)(BlockDriverState *bs,
int64_t sector_num, QEMUIOVector *qiov, int nb_sectors,
BlockCompletionFunc *cb, void *opaque);
BlockAIOCB *(*bdrv_aio_preadv)(BlockDriverState *bs,
uint64_t offset, uint64_t bytes, QEMUIOVector *qiov, int flags,
BlockCompletionFunc *cb, void *opaque);
BlockAIOCB *(*bdrv_aio_writev)(BlockDriverState *bs,
int64_t sector_num, QEMUIOVector *qiov, int nb_sectors,
BlockCompletionFunc *cb, void *opaque);
BlockAIOCB *(*bdrv_aio_pwritev)(BlockDriverState *bs,
uint64_t offset, uint64_t bytes, QEMUIOVector *qiov, int flags,
BlockCompletionFunc *cb, void *opaque);
BlockAIOCB *(*bdrv_aio_flush)(BlockDriverState *bs,
BlockCompletionFunc *cb, void *opaque);
BlockAIOCB *(*bdrv_aio_pdiscard)(BlockDriverState *bs,