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block: Convert bdrv_co_discard() to byte-based

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Another step towards byte-based interfaces everywhere.  Replace
the sector-based bdrv_co_discard() with a new byte-based
bdrv_co_pdiscard(), which silently ignores any unaligned head
or tail.  Driver callbacks will be converted in followup patches.

By calculating the alignment outside of the loop, and clamping
the max discard to an aligned value, we can simplify the actions
done within the loop.

Signed-off-by: Eric Blake <eblake@redhat.com>
Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>
Message-id: 1468624988-423-2-git-send-email-eblake@redhat.com
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
This commit is contained in:
Eric Blake 2016-07-15 17:22:50 -06:00 • committed by Stefan Hajnoczi
parent 6bd01f14db
commit 9f1963b3f7
5 changed files with 42 additions and 36 deletions
Download patch file Download diff file Expand all files Collapse all files

67
block/io.c
View file

@ -2199,7 +2199,8 @@ static void coroutine_fn bdrv_aio_discard_co_entry(void *opaque)
BlockAIOCBCoroutine *acb = opaque;
BlockDriverState *bs = acb->common.bs;
acb->req.error = bdrv_co_discard(bs, acb->req.sector, acb->req.nb_sectors);
acb->req.error = bdrv_co_pdiscard(bs, acb->req.sector << BDRV_SECTOR_BITS,
acb->req.nb_sectors << BDRV_SECTOR_BITS);
bdrv_co_complete(acb);
}
@ -2398,20 +2399,22 @@ static void coroutine_fn bdrv_discard_co_entry(void *opaque)
{
DiscardCo *rwco = opaque;
rwco->ret = bdrv_co_discard(rwco->bs, rwco->sector_num, rwco->nb_sectors);
rwco->ret = bdrv_co_pdiscard(rwco->bs, rwco->sector_num << BDRV_SECTOR_BITS,
rwco->nb_sectors << BDRV_SECTOR_BITS);
}
int coroutine_fn bdrv_co_discard(BlockDriverState *bs, int64_t sector_num,
int nb_sectors)
int coroutine_fn bdrv_co_pdiscard(BlockDriverState *bs, int64_t offset,
int count)
{
BdrvTrackedRequest req;
int max_discard, ret;
int max_pdiscard, ret;
int head, align;
if (!bs->drv) {
return -ENOMEDIUM;
}
ret = bdrv_check_request(bs, sector_num, nb_sectors);
ret = bdrv_check_byte_request(bs, offset, count);
if (ret < 0) {
return ret;
} else if (bs->read_only) {
@ -2428,45 +2431,45 @@ int coroutine_fn bdrv_co_discard(BlockDriverState *bs, int64_t sector_num,
return 0;
}
tracked_request_begin(&req, bs, sector_num << BDRV_SECTOR_BITS,
nb_sectors << BDRV_SECTOR_BITS, BDRV_TRACKED_DISCARD);
/* Discard is advisory, so ignore any unaligned head or tail */
align = MAX(BDRV_SECTOR_SIZE,
MAX(bs->bl.pdiscard_alignment, bs->bl.request_alignment));
assert(is_power_of_2(align));
head = MIN(count, -offset & (align - 1));
if (head) {
count -= head;
offset += head;
}
count = QEMU_ALIGN_DOWN(count, align);
if (!count) {
return 0;
}
tracked_request_begin(&req, bs, offset, count, BDRV_TRACKED_DISCARD);
ret = notifier_with_return_list_notify(&bs->before_write_notifiers, &req);
if (ret < 0) {
goto out;
}
max_discard = MIN_NON_ZERO(bs->bl.max_pdiscard >> BDRV_SECTOR_BITS,
BDRV_REQUEST_MAX_SECTORS);
while (nb_sectors > 0) {
max_pdiscard = QEMU_ALIGN_DOWN(MIN_NON_ZERO(bs->bl.max_pdiscard, INT_MAX),
align);
while (count > 0) {
int ret;
int num = nb_sectors;
int discard_alignment = bs->bl.pdiscard_alignment >> BDRV_SECTOR_BITS;
/* align request */
if (discard_alignment &&
num >= discard_alignment &&
sector_num % discard_alignment) {
if (num > discard_alignment) {
num = discard_alignment;
}
num -= sector_num % discard_alignment;
}
/* limit request size */
if (num > max_discard) {
num = max_discard;
}
int num = MIN(count, max_pdiscard);
if (bs->drv->bdrv_co_discard) {
ret = bs->drv->bdrv_co_discard(bs, sector_num, num);
ret = bs->drv->bdrv_co_discard(bs, offset >> BDRV_SECTOR_BITS,
num >> BDRV_SECTOR_BITS);
} else {
BlockAIOCB *acb;
CoroutineIOCompletion co = {
.coroutine = qemu_coroutine_self(),
};
acb = bs->drv->bdrv_aio_discard(bs, sector_num, nb_sectors,
acb = bs->drv->bdrv_aio_discard(bs, offset >> BDRV_SECTOR_BITS,
num >> BDRV_SECTOR_BITS,
bdrv_co_io_em_complete, &co);
if (acb == NULL) {
ret = -EIO;
@ -2480,8 +2483,8 @@ int coroutine_fn bdrv_co_discard(BlockDriverState *bs, int64_t sector_num,
goto out;
}
sector_num += num;
nb_sectors -= num;
offset += num;
count -= num;
}
ret = 0;
out: