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block: Add backend_defaults property

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backend_defaults property allow users to control if default block
properties should be decided with backend information.

If it is off, any backend information will be discarded, which is
suitable if you plan to perform live migration to a different disk backend.

If it is on, a block device may utilize backend information more
aggressively.

By default, it is auto, which uses backend information for block
sizes and ignores the others, which is consistent with the older
versions.

Signed-off-by: Akihiko Odaki <akihiko.odaki@gmail.com>
Message-id: 20210705130458.97642-2-akihiko.odaki@gmail.com
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
This commit is contained in:
Akihiko Odaki 2021-07-05 22:04:57 +09:00 • committed by Stefan Hajnoczi
parent 0dfc7af2b2
commit 12a521b56d
3 changed files with 79 additions and 4 deletions
Download patch file Download diff file Expand all files Collapse all files

42
hw/block/block.c
View file

@ -65,24 +65,58 @@ bool blkconf_blocksizes(BlockConf *conf, Error **errp)
{
BlockBackend *blk = conf->blk;
BlockSizes blocksizes;
int backend_ret;
BlockDriverState *bs;
bool use_blocksizes;
bool use_bs;
switch (conf->backend_defaults) {
case ON_OFF_AUTO_AUTO:
use_blocksizes = !blk_probe_blocksizes(blk, &blocksizes);
use_bs = false;
break;
case ON_OFF_AUTO_ON:
use_blocksizes = !blk_probe_blocksizes(blk, &blocksizes);
bs = blk_bs(blk);
use_bs = bs;
break;
case ON_OFF_AUTO_OFF:
use_blocksizes = false;
use_bs = false;
break;
default:
abort();
}
backend_ret = blk_probe_blocksizes(blk, &blocksizes);
/* fill in detected values if they are not defined via qemu command line */
if (!conf->physical_block_size) {
if (!backend_ret) {
if (use_blocksizes) {
conf->physical_block_size = blocksizes.phys;
} else {
conf->physical_block_size = BDRV_SECTOR_SIZE;
}
}
if (!conf->logical_block_size) {
if (!backend_ret) {
if (use_blocksizes) {
conf->logical_block_size = blocksizes.log;
} else {
conf->logical_block_size = BDRV_SECTOR_SIZE;
}
}
if (use_bs) {
if (!conf->opt_io_size) {
conf->opt_io_size = bs->bl.opt_transfer;
}
if (conf->discard_granularity == -1) {
if (bs->bl.pdiscard_alignment) {
conf->discard_granularity = bs->bl.pdiscard_alignment;
} else if (bs->bl.request_alignment != 1) {
conf->discard_granularity = bs->bl.request_alignment;
}
}
}
if (conf->logical_block_size > conf->physical_block_size) {
error_setg(errp,