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block: Split bdrv_merge_limits() from bdrv_refresh_limits()

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During bdrv_merge_limits(), we were computing initial limits
based on another BDS in two places.  At first glance, the two
computations are not identical (one is doing straight copying,
the other is doing merging towards or away from zero) - but
when you realize that the first round is starting with all-0
memory, all of the merging happens to work.  Factoring out the
merging makes it easier to track how two BDS limits are merged,
in case we have future reasons to merge in even more limits.

Signed-off-by: Eric Blake <eblake@redhat.com>
Reviewed-by: Fam Zheng <famz@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
This commit is contained in:
Eric Blake 2016-06-23 16:37:23 -06:00 committed by Kevin Wolf
parent ad82be2f4f
commit d9e0dfa246
1 changed files with 13 additions and 18 deletions
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31
block/io.c
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@ -67,6 +67,17 @@ static void bdrv_parent_drained_end(BlockDriverState *bs)
}
}
static void bdrv_merge_limits(BlockLimits *dst, const BlockLimits *src)
{
dst->opt_transfer = MAX(dst->opt_transfer, src->opt_transfer);
dst->max_transfer = MIN_NON_ZERO(dst->max_transfer, src->max_transfer);
dst->opt_mem_alignment = MAX(dst->opt_mem_alignment,
src->opt_mem_alignment);
dst->min_mem_alignment = MAX(dst->min_mem_alignment,
src->min_mem_alignment);
dst->max_iov = MIN_NON_ZERO(dst->max_iov, src->max_iov);
}
void bdrv_refresh_limits(BlockDriverState *bs, Error **errp)
{
BlockDriver *drv = bs->drv;
@ -88,11 +99,7 @@ void bdrv_refresh_limits(BlockDriverState *bs, Error **errp)
error_propagate(errp, local_err);
return;
}
bs->bl.opt_transfer = bs->file->bs->bl.opt_transfer;
bs->bl.max_transfer = bs->file->bs->bl.max_transfer;
bs->bl.min_mem_alignment = bs->file->bs->bl.min_mem_alignment;
bs->bl.opt_mem_alignment = bs->file->bs->bl.opt_mem_alignment;
bs->bl.max_iov = bs->file->bs->bl.max_iov;
bdrv_merge_limits(&bs->bl, &bs->file->bs->bl);
} else {
bs->bl.min_mem_alignment = 512;
bs->bl.opt_mem_alignment = getpagesize();
@ -107,19 +114,7 @@ void bdrv_refresh_limits(BlockDriverState *bs, Error **errp)
error_propagate(errp, local_err);
return;
}
bs->bl.opt_transfer = MAX(bs->bl.opt_transfer,
bs->backing->bs->bl.opt_transfer);
bs->bl.max_transfer = MIN_NON_ZERO(bs->bl.max_transfer,
bs->backing->bs->bl.max_transfer);
bs->bl.opt_mem_alignment =
MAX(bs->bl.opt_mem_alignment,
bs->backing->bs->bl.opt_mem_alignment);
bs->bl.min_mem_alignment =
MAX(bs->bl.min_mem_alignment,
bs->backing->bs->bl.min_mem_alignment);
bs->bl.max_iov =
MIN(bs->bl.max_iov,
bs->backing->bs->bl.max_iov);
bdrv_merge_limits(&bs->bl, &bs->backing->bs->bl);
}
/* Then let the driver override it */