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block: change default for discard and write zeroes to INT_MAX

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do not trim requests if the driver does not supply a limit
through BlockLimits. For write zeroes we still keep a limit
for the unsupported path to avoid allocating a big bounce buffer.

Suggested-by: Kevin Wolf <kwolf@redhat.com>
Suggested-by: Denis V. Lunev <den@openvz.org>
Signed-off-by: Peter Lieven <pl@kamp.de>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
This commit is contained in:
Peter Lieven 2015-02-02 15:48:34 +01:00 committed by Kevin Wolf
parent 1cdc3239f1
commit 98764152ad
1 changed files with 4 additions and 12 deletions
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16
block.c
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@ -3192,10 +3192,7 @@ int coroutine_fn bdrv_co_copy_on_readv(BlockDriverState *bs,
BDRV_REQ_COPY_ON_READ);
}
/* if no limit is specified in the BlockLimits use a default
* of 32768 512-byte sectors (16 MiB) per request.
*/
#define MAX_WRITE_ZEROES_DEFAULT 32768
#define MAX_WRITE_ZEROES_BOUNCE_BUFFER 32768
static int coroutine_fn bdrv_co_do_write_zeroes(BlockDriverState *bs,
int64_t sector_num, int nb_sectors, BdrvRequestFlags flags)
@ -3206,7 +3203,7 @@ static int coroutine_fn bdrv_co_do_write_zeroes(BlockDriverState *bs,
int ret = 0;
int max_write_zeroes = bs->bl.max_write_zeroes ?
bs->bl.max_write_zeroes : MAX_WRITE_ZEROES_DEFAULT;
bs->bl.max_write_zeroes : INT_MAX;
while (nb_sectors > 0 && !ret) {
int num = nb_sectors;
@ -3242,7 +3239,7 @@ static int coroutine_fn bdrv_co_do_write_zeroes(BlockDriverState *bs,
if (ret == -ENOTSUP) {
/* Fall back to bounce buffer if write zeroes is unsupported */
int max_xfer_len = MIN_NON_ZERO(bs->bl.max_transfer_length,
MAX_WRITE_ZEROES_DEFAULT);
MAX_WRITE_ZEROES_BOUNCE_BUFFER);
num = MIN(num, max_xfer_len);
iov.iov_len = num * BDRV_SECTOR_SIZE;
if (iov.iov_base == NULL) {
@ -5097,11 +5094,6 @@ static void coroutine_fn bdrv_discard_co_entry(void *opaque)
rwco->ret = bdrv_co_discard(rwco->bs, rwco->sector_num, rwco->nb_sectors);
}
/* if no limit is specified in the BlockLimits use a default
* of 32768 512-byte sectors (16 MiB) per request.
*/
#define MAX_DISCARD_DEFAULT 32768
int coroutine_fn bdrv_co_discard(BlockDriverState *bs, int64_t sector_num,
int nb_sectors)
{
@ -5126,7 +5118,7 @@ int coroutine_fn bdrv_co_discard(BlockDriverState *bs, int64_t sector_num,
return 0;
}
max_discard = bs->bl.max_discard ? bs->bl.max_discard : MAX_DISCARD_DEFAULT;
max_discard = bs->bl.max_discard ? bs->bl.max_discard : INT_MAX;
while (nb_sectors > 0) {
int ret;
int num = nb_sectors;