copy-on-read: add filter drop function

Provide API for the COR-filter removal. Also, drop the filter child
permissions for an inactive state when the filter node is being
removed.
To insert the filter, the block generic layer function
bdrv_insert_node() can be used.
The new function bdrv_cor_filter_drop() may be considered as an
intermediate solution before the QEMU permission update system has
overhauled. Then we are able to implement the API function
bdrv_remove_node() on the block generic layer.

Signed-off-by: Andrey Shinkevich <andrey.shinkevich@virtuozzo.com>
Reviewed-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
Reviewed-by: Max Reitz <mreitz@redhat.com>
Message-Id: <20201216061703.70908-4-vsementsov@virtuozzo.com>
Signed-off-by: Max Reitz <mreitz@redhat.com>
This commit is contained in:
Andrey Shinkevich 2020-12-16 09:16:53 +03:00 committed by Max Reitz
parent 8872ef78ab
commit 16e09a21af
2 changed files with 88 additions and 0 deletions

View File

@ -23,11 +23,20 @@
#include "qemu/osdep.h" #include "qemu/osdep.h"
#include "block/block_int.h" #include "block/block_int.h"
#include "qemu/module.h" #include "qemu/module.h"
#include "qapi/error.h"
#include "block/copy-on-read.h"
typedef struct BDRVStateCOR {
bool active;
} BDRVStateCOR;
static int cor_open(BlockDriverState *bs, QDict *options, int flags, static int cor_open(BlockDriverState *bs, QDict *options, int flags,
Error **errp) Error **errp)
{ {
BDRVStateCOR *state = bs->opaque;
bs->file = bdrv_open_child(NULL, options, "file", bs, &child_of_bds, bs->file = bdrv_open_child(NULL, options, "file", bs, &child_of_bds,
BDRV_CHILD_FILTERED | BDRV_CHILD_PRIMARY, BDRV_CHILD_FILTERED | BDRV_CHILD_PRIMARY,
false, errp); false, errp);
@ -42,6 +51,13 @@ static int cor_open(BlockDriverState *bs, QDict *options, int flags,
((BDRV_REQ_FUA | BDRV_REQ_MAY_UNMAP | BDRV_REQ_NO_FALLBACK) & ((BDRV_REQ_FUA | BDRV_REQ_MAY_UNMAP | BDRV_REQ_NO_FALLBACK) &
bs->file->bs->supported_zero_flags); bs->file->bs->supported_zero_flags);
state->active = true;
/*
* We don't need to call bdrv_child_refresh_perms() now as the permissions
* will be updated later when the filter node gets its parent.
*/
return 0; return 0;
} }
@ -57,6 +73,17 @@ static void cor_child_perm(BlockDriverState *bs, BdrvChild *c,
uint64_t perm, uint64_t shared, uint64_t perm, uint64_t shared,
uint64_t *nperm, uint64_t *nshared) uint64_t *nperm, uint64_t *nshared)
{ {
BDRVStateCOR *s = bs->opaque;
if (!s->active) {
/*
* While the filter is being removed
*/
*nperm = 0;
*nshared = BLK_PERM_ALL;
return;
}
*nperm = perm & PERM_PASSTHROUGH; *nperm = perm & PERM_PASSTHROUGH;
*nshared = (shared & PERM_PASSTHROUGH) | PERM_UNCHANGED; *nshared = (shared & PERM_PASSTHROUGH) | PERM_UNCHANGED;
@ -135,6 +162,7 @@ static void cor_lock_medium(BlockDriverState *bs, bool locked)
static BlockDriver bdrv_copy_on_read = { static BlockDriver bdrv_copy_on_read = {
.format_name = "copy-on-read", .format_name = "copy-on-read",
.instance_size = sizeof(BDRVStateCOR),
.bdrv_open = cor_open, .bdrv_open = cor_open,
.bdrv_child_perm = cor_child_perm, .bdrv_child_perm = cor_child_perm,
@ -154,6 +182,34 @@ static BlockDriver bdrv_copy_on_read = {
.is_filter = true, .is_filter = true,
}; };
void bdrv_cor_filter_drop(BlockDriverState *cor_filter_bs)
{
BdrvChild *child;
BlockDriverState *bs;
BDRVStateCOR *s = cor_filter_bs->opaque;
child = bdrv_filter_child(cor_filter_bs);
if (!child) {
return;
}
bs = child->bs;
/* Retain the BDS until we complete the graph change. */
bdrv_ref(bs);
/* Hold a guest back from writing while permissions are being reset. */
bdrv_drained_begin(bs);
/* Drop permissions before the graph change. */
s->active = false;
bdrv_child_refresh_perms(cor_filter_bs, child, &error_abort);
bdrv_replace_node(cor_filter_bs, bs, &error_abort);
bdrv_drained_end(bs);
bdrv_unref(bs);
bdrv_unref(cor_filter_bs);
}
static void bdrv_copy_on_read_init(void) static void bdrv_copy_on_read_init(void)
{ {
bdrv_register(&bdrv_copy_on_read); bdrv_register(&bdrv_copy_on_read);

32
block/copy-on-read.h Normal file
View File

@ -0,0 +1,32 @@
/*
* Copy-on-read filter block driver
*
* The filter driver performs Copy-On-Read (COR) operations
*
* Copyright (c) 2018-2020 Virtuozzo International GmbH.
*
* Author:
* Andrey Shinkevich <andrey.shinkevich@virtuozzo.com>
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation; either version 2 of the License, or
* (at your option) any later version.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with this program. If not, see <http://www.gnu.org/licenses/>.
*/
#ifndef BLOCK_COPY_ON_READ
#define BLOCK_COPY_ON_READ
#include "block/block_int.h"
void bdrv_cor_filter_drop(BlockDriverState *cor_filter_bs);
#endif /* BLOCK_COPY_ON_READ */