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qapi: copy-on-read filter: add 'bottom' option
Add an option to limit copy-on-read operations to specified sub-chain of backing-chain, to make copy-on-read filter useful for block-stream job. Suggested-by: Max Reitz <mreitz@redhat.com> Suggested-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com> Signed-off-by: Andrey Shinkevich <andrey.shinkevich@virtuozzo.com> Signed-off-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com> [vsementsov: change subject, modified to freeze the chain, do some fixes] Message-Id: <20201216061703.70908-6-vsementsov@virtuozzo.com> Signed-off-by: Max Reitz <mreitz@redhat.com>
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@ -24,18 +24,24 @@
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#include "block/block_int.h"
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#include "qemu/module.h"
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#include "qapi/error.h"
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#include "qapi/qmp/qdict.h"
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#include "block/copy-on-read.h"
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typedef struct BDRVStateCOR {
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bool active;
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BlockDriverState *bottom_bs;
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bool chain_frozen;
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} BDRVStateCOR;
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static int cor_open(BlockDriverState *bs, QDict *options, int flags,
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Error **errp)
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{
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BlockDriverState *bottom_bs = NULL;
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BDRVStateCOR *state = bs->opaque;
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/* Find a bottom node name, if any */
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const char *bottom_node = qdict_get_try_str(options, "bottom");
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bs->file = bdrv_open_child(NULL, options, "file", bs, &child_of_bds,
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BDRV_CHILD_FILTERED | BDRV_CHILD_PRIMARY,
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@ -51,7 +57,38 @@ static int cor_open(BlockDriverState *bs, QDict *options, int flags,
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((BDRV_REQ_FUA | BDRV_REQ_MAY_UNMAP | BDRV_REQ_NO_FALLBACK) &
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bs->file->bs->supported_zero_flags);
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if (bottom_node) {
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bottom_bs = bdrv_find_node(bottom_node);
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if (!bottom_bs) {
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error_setg(errp, "Bottom node '%s' not found", bottom_node);
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qdict_del(options, "bottom");
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return -EINVAL;
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}
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qdict_del(options, "bottom");
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if (!bottom_bs->drv) {
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error_setg(errp, "Bottom node '%s' not opened", bottom_node);
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return -EINVAL;
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}
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if (bottom_bs->drv->is_filter) {
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error_setg(errp, "Bottom node '%s' is a filter", bottom_node);
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return -EINVAL;
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}
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if (bdrv_freeze_backing_chain(bs, bottom_bs, errp) < 0) {
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return -EINVAL;
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}
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state->chain_frozen = true;
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/*
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* We do freeze the chain, so it shouldn't be removed. Still, storing a
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* pointer worth bdrv_ref().
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*/
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bdrv_ref(bottom_bs);
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}
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state->active = true;
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state->bottom_bs = bottom_bs;
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/*
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* We don't need to call bdrv_child_refresh_perms() now as the permissions
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@ -107,8 +144,46 @@ static int coroutine_fn cor_co_preadv_part(BlockDriverState *bs,
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size_t qiov_offset,
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int flags)
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{
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return bdrv_co_preadv_part(bs->file, offset, bytes, qiov, qiov_offset,
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flags | BDRV_REQ_COPY_ON_READ);
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int64_t n;
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int local_flags;
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int ret;
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BDRVStateCOR *state = bs->opaque;
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if (!state->bottom_bs) {
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return bdrv_co_preadv_part(bs->file, offset, bytes, qiov, qiov_offset,
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flags | BDRV_REQ_COPY_ON_READ);
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}
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while (bytes) {
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local_flags = flags;
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/* In case of failure, try to copy-on-read anyway */
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ret = bdrv_is_allocated(bs->file->bs, offset, bytes, &n);
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if (ret <= 0) {
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ret = bdrv_is_allocated_above(bdrv_backing_chain_next(bs->file->bs),
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state->bottom_bs, true, offset,
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n, &n);
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if (ret > 0 || ret < 0) {
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local_flags |= BDRV_REQ_COPY_ON_READ;
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}
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/* Finish earlier if the end of a backing file has been reached */
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if (n == 0) {
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break;
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}
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}
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ret = bdrv_co_preadv_part(bs->file, offset, n, qiov, qiov_offset,
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local_flags);
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if (ret < 0) {
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return ret;
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}
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offset += n;
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qiov_offset += n;
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bytes -= n;
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}
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return 0;
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}
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@ -160,11 +235,25 @@ static void cor_lock_medium(BlockDriverState *bs, bool locked)
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}
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static void cor_close(BlockDriverState *bs)
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{
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BDRVStateCOR *s = bs->opaque;
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if (s->chain_frozen) {
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s->chain_frozen = false;
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bdrv_unfreeze_backing_chain(bs, s->bottom_bs);
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}
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bdrv_unref(s->bottom_bs);
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}
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static BlockDriver bdrv_copy_on_read = {
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.format_name = "copy-on-read",
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.instance_size = sizeof(BDRVStateCOR),
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.bdrv_open = cor_open,
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.bdrv_close = cor_close,
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.bdrv_child_perm = cor_child_perm,
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.bdrv_getlength = cor_getlength,
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@ -201,6 +290,11 @@ void bdrv_cor_filter_drop(BlockDriverState *cor_filter_bs)
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bdrv_drained_begin(bs);
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/* Drop permissions before the graph change. */
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s->active = false;
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/* unfreeze, as otherwise bdrv_replace_node() will fail */
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if (s->chain_frozen) {
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s->chain_frozen = false;
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bdrv_unfreeze_backing_chain(cor_filter_bs, s->bottom_bs);
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}
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bdrv_child_refresh_perms(cor_filter_bs, child, &error_abort);
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bdrv_replace_node(cor_filter_bs, bs, &error_abort);
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@ -3959,6 +3959,24 @@
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'data': { 'throttle-group': 'str',
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'file' : 'BlockdevRef'
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} }
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##
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# @BlockdevOptionsCor:
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#
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# Driver specific block device options for the copy-on-read driver.
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#
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# @bottom: The name of a non-filter node (allocation-bearing layer) that
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# limits the COR operations in the backing chain (inclusive), so
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# that no data below this node will be copied by this filter.
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# If option is absent, the limit is not applied, so that data
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# from all backing layers may be copied.
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#
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# Since: 6.0
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##
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{ 'struct': 'BlockdevOptionsCor',
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'base': 'BlockdevOptionsGenericFormat',
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'data': { '*bottom': 'str' } }
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##
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# @BlockdevOptions:
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#
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@ -4011,7 +4029,7 @@
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'bochs': 'BlockdevOptionsGenericFormat',
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'cloop': 'BlockdevOptionsGenericFormat',
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'compress': 'BlockdevOptionsGenericFormat',
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'copy-on-read':'BlockdevOptionsGenericFormat',
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'copy-on-read':'BlockdevOptionsCor',
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'dmg': 'BlockdevOptionsGenericFormat',
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'file': 'BlockdevOptionsFile',
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'ftp': 'BlockdevOptionsCurlFtp',
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