qemu/block/backup-top.c

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/*
* backup-top filter driver
*
* The driver performs Copy-Before-Write (CBW) operation: it is injected above
* some node, and before each write it copies _old_ data to the target node.
*
* Copyright (c) 2018-2019 Virtuozzo International GmbH.
*
* Author:
* Sementsov-Ogievskiy Vladimir <vsementsov@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/>.
*/
#include "qemu/osdep.h"
#include "sysemu/block-backend.h"
#include "qemu/cutils.h"
#include "qapi/error.h"
#include "block/block_int.h"
#include "block/qdict.h"
#include "block/block-copy.h"
#include "block/backup-top.h"
typedef struct BDRVBackupTopState {
BlockCopyState *bcs;
BdrvChild *target;
bool active;
} BDRVBackupTopState;
static coroutine_fn int backup_top_co_preadv(
BlockDriverState *bs, uint64_t offset, uint64_t bytes,
QEMUIOVector *qiov, int flags)
{
return bdrv_co_preadv(bs->backing, offset, bytes, qiov, flags);
}
static coroutine_fn int backup_top_cbw(BlockDriverState *bs, uint64_t offset,
uint64_t bytes)
{
block/backup: use backup-top instead of write notifiers Drop write notifiers and use filter node instead. = Changes = 1. Add filter-node-name argument for backup qmp api. We have to do it in this commit, as 257 needs to be fixed. 2. There are no more write notifiers here, so is_write_notifier parameter is dropped from block-copy paths. 3. To sync with in-flight requests at job finish we now have drained removing of the filter, we don't need rw-lock. 4. Block-copy is now using BdrvChildren instead of BlockBackends 5. As backup-top owns these children, we also move block-copy state into backup-top's ownership. = Iotest changes = 56: op-blocker doesn't shoot now, as we set it on source, but then check on filter, when trying to start second backup. To keep the test we instead can catch another collision: both jobs will get 'drive0' job-id, as job-id parameter is unspecified. To prevent interleaving with file-posix locks (as they are dependent on config) let's use another target for second backup. Also, it's obvious now that we'd like to drop this op-blocker at all and add a test-case for two backups from one node (to different destinations) actually works. But not in these series. 141: Output changed: prepatch, "Node is in use" comes from bdrv_has_blk check inside qmp_blockdev_del. But we've dropped block-copy blk objects, so no more blk objects on source bs (job blk is on backup-top filter bs). New message is from op-blocker, which is the next check in qmp_blockdev_add. 257: The test wants to emulate guest write during backup. They should go to filter node, not to original source node, of course. Therefore we need to specify filter node name and use it. Signed-off-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com> Message-id: 20191001131409.14202-6-vsementsov@virtuozzo.com Reviewed-by: Max Reitz <mreitz@redhat.com> Signed-off-by: Max Reitz <mreitz@redhat.com>
2019-10-01 16:14:09 +03:00
BDRVBackupTopState *s = bs->opaque;
uint64_t end = QEMU_ALIGN_UP(offset + bytes, s->bcs->cluster_size);
uint64_t off = QEMU_ALIGN_DOWN(offset, s->bcs->cluster_size);
block/backup: use backup-top instead of write notifiers Drop write notifiers and use filter node instead. = Changes = 1. Add filter-node-name argument for backup qmp api. We have to do it in this commit, as 257 needs to be fixed. 2. There are no more write notifiers here, so is_write_notifier parameter is dropped from block-copy paths. 3. To sync with in-flight requests at job finish we now have drained removing of the filter, we don't need rw-lock. 4. Block-copy is now using BdrvChildren instead of BlockBackends 5. As backup-top owns these children, we also move block-copy state into backup-top's ownership. = Iotest changes = 56: op-blocker doesn't shoot now, as we set it on source, but then check on filter, when trying to start second backup. To keep the test we instead can catch another collision: both jobs will get 'drive0' job-id, as job-id parameter is unspecified. To prevent interleaving with file-posix locks (as they are dependent on config) let's use another target for second backup. Also, it's obvious now that we'd like to drop this op-blocker at all and add a test-case for two backups from one node (to different destinations) actually works. But not in these series. 141: Output changed: prepatch, "Node is in use" comes from bdrv_has_blk check inside qmp_blockdev_del. But we've dropped block-copy blk objects, so no more blk objects on source bs (job blk is on backup-top filter bs). New message is from op-blocker, which is the next check in qmp_blockdev_add. 257: The test wants to emulate guest write during backup. They should go to filter node, not to original source node, of course. Therefore we need to specify filter node name and use it. Signed-off-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com> Message-id: 20191001131409.14202-6-vsementsov@virtuozzo.com Reviewed-by: Max Reitz <mreitz@redhat.com> Signed-off-by: Max Reitz <mreitz@redhat.com>
2019-10-01 16:14:09 +03:00
return block_copy(s->bcs, off, end - off, NULL);
}
static int coroutine_fn backup_top_co_pdiscard(BlockDriverState *bs,
int64_t offset, int bytes)
{
int ret = backup_top_cbw(bs, offset, bytes);
if (ret < 0) {
return ret;
}
return bdrv_co_pdiscard(bs->backing, offset, bytes);
}
static int coroutine_fn backup_top_co_pwrite_zeroes(BlockDriverState *bs,
int64_t offset, int bytes, BdrvRequestFlags flags)
{
int ret = backup_top_cbw(bs, offset, bytes);
if (ret < 0) {
return ret;
}
return bdrv_co_pwrite_zeroes(bs->backing, offset, bytes, flags);
}
static coroutine_fn int backup_top_co_pwritev(BlockDriverState *bs,
uint64_t offset,
uint64_t bytes,
QEMUIOVector *qiov, int flags)
{
if (!(flags & BDRV_REQ_WRITE_UNCHANGED)) {
int ret = backup_top_cbw(bs, offset, bytes);
if (ret < 0) {
return ret;
}
}
return bdrv_co_pwritev(bs->backing, offset, bytes, qiov, flags);
}
static int coroutine_fn backup_top_co_flush(BlockDriverState *bs)
{
if (!bs->backing) {
return 0;
}
return bdrv_co_flush(bs->backing->bs);
}
static void backup_top_refresh_filename(BlockDriverState *bs)
{
if (bs->backing == NULL) {
/*
* we can be here after failed bdrv_attach_child in
* bdrv_set_backing_hd
*/
return;
}
pstrcpy(bs->exact_filename, sizeof(bs->exact_filename),
bs->backing->bs->filename);
}
static void backup_top_child_perm(BlockDriverState *bs, BdrvChild *c,
const BdrvChildRole *role,
BlockReopenQueue *reopen_queue,
uint64_t perm, uint64_t shared,
uint64_t *nperm, uint64_t *nshared)
{
BDRVBackupTopState *s = bs->opaque;
if (!s->active) {
/*
* The filter node may be in process of bdrv_append(), which firstly do
* bdrv_set_backing_hd() and then bdrv_replace_node(). This means that
* we can't unshare BLK_PERM_WRITE during bdrv_append() operation. So,
* let's require nothing during bdrv_append() and refresh permissions
* after it (see bdrv_backup_top_append()).
*/
*nperm = 0;
*nshared = BLK_PERM_ALL;
return;
}
if (role == &child_file) {
/*
* Target child
*
* Share write to target (child_file), to not interfere
* with guest writes to its disk which may be in target backing chain.
*/
*nshared = BLK_PERM_ALL;
*nperm = BLK_PERM_WRITE;
} else {
/* Source child */
bdrv_filter_default_perms(bs, c, role, reopen_queue, perm, shared,
nperm, nshared);
if (perm & BLK_PERM_WRITE) {
*nperm = *nperm | BLK_PERM_CONSISTENT_READ;
}
*nshared &= ~BLK_PERM_WRITE;
}
}
BlockDriver bdrv_backup_top_filter = {
.format_name = "backup-top",
.instance_size = sizeof(BDRVBackupTopState),
.bdrv_co_preadv = backup_top_co_preadv,
.bdrv_co_pwritev = backup_top_co_pwritev,
.bdrv_co_pwrite_zeroes = backup_top_co_pwrite_zeroes,
.bdrv_co_pdiscard = backup_top_co_pdiscard,
.bdrv_co_flush = backup_top_co_flush,
.bdrv_co_block_status = bdrv_co_block_status_from_backing,
.bdrv_refresh_filename = backup_top_refresh_filename,
.bdrv_child_perm = backup_top_child_perm,
.is_filter = true,
};
BlockDriverState *bdrv_backup_top_append(BlockDriverState *source,
BlockDriverState *target,
const char *filter_node_name,
uint64_t cluster_size,
BdrvRequestFlags write_flags,
BlockCopyState **bcs,
Error **errp)
{
Error *local_err = NULL;
BDRVBackupTopState *state;
BlockDriverState *top = bdrv_new_open_driver(&bdrv_backup_top_filter,
filter_node_name,
BDRV_O_RDWR, errp);
bool appended = false;
if (!top) {
return NULL;
}
top->total_sectors = source->total_sectors;
state = top->opaque;
bdrv_ref(target);
state->target = bdrv_attach_child(top, target, "target", &child_file, errp);
if (!state->target) {
bdrv_unref(target);
bdrv_unref(top);
return NULL;
}
bdrv_drained_begin(source);
bdrv_ref(top);
bdrv_append(top, source, &local_err);
if (local_err) {
error_prepend(&local_err, "Cannot append backup-top filter: ");
goto fail;
}
appended = true;
/*
* bdrv_append() finished successfully, now we can require permissions
* we want.
*/
state->active = true;
bdrv_child_refresh_perms(top, top->backing, &local_err);
if (local_err) {
error_prepend(&local_err,
"Cannot set permissions for backup-top filter: ");
goto fail;
}
block/backup: use backup-top instead of write notifiers Drop write notifiers and use filter node instead. = Changes = 1. Add filter-node-name argument for backup qmp api. We have to do it in this commit, as 257 needs to be fixed. 2. There are no more write notifiers here, so is_write_notifier parameter is dropped from block-copy paths. 3. To sync with in-flight requests at job finish we now have drained removing of the filter, we don't need rw-lock. 4. Block-copy is now using BdrvChildren instead of BlockBackends 5. As backup-top owns these children, we also move block-copy state into backup-top's ownership. = Iotest changes = 56: op-blocker doesn't shoot now, as we set it on source, but then check on filter, when trying to start second backup. To keep the test we instead can catch another collision: both jobs will get 'drive0' job-id, as job-id parameter is unspecified. To prevent interleaving with file-posix locks (as they are dependent on config) let's use another target for second backup. Also, it's obvious now that we'd like to drop this op-blocker at all and add a test-case for two backups from one node (to different destinations) actually works. But not in these series. 141: Output changed: prepatch, "Node is in use" comes from bdrv_has_blk check inside qmp_blockdev_del. But we've dropped block-copy blk objects, so no more blk objects on source bs (job blk is on backup-top filter bs). New message is from op-blocker, which is the next check in qmp_blockdev_add. 257: The test wants to emulate guest write during backup. They should go to filter node, not to original source node, of course. Therefore we need to specify filter node name and use it. Signed-off-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com> Message-id: 20191001131409.14202-6-vsementsov@virtuozzo.com Reviewed-by: Max Reitz <mreitz@redhat.com> Signed-off-by: Max Reitz <mreitz@redhat.com>
2019-10-01 16:14:09 +03:00
state->bcs = block_copy_state_new(top->backing, state->target,
cluster_size, write_flags, &local_err);
if (local_err) {
error_prepend(&local_err, "Cannot create block-copy-state: ");
goto fail;
}
*bcs = state->bcs;
bdrv_drained_end(source);
return top;
fail:
if (appended) {
state->active = false;
bdrv_backup_top_drop(top);
} else {
bdrv_unref(top);
}
bdrv_drained_end(source);
error_propagate(errp, local_err);
return NULL;
}
void bdrv_backup_top_drop(BlockDriverState *bs)
{
BDRVBackupTopState *s = bs->opaque;
bdrv_drained_begin(bs);
block_copy_state_free(s->bcs);
s->active = false;
bdrv_child_refresh_perms(bs, bs->backing, &error_abort);
bdrv_replace_node(bs, backing_bs(bs), &error_abort);
bdrv_set_backing_hd(bs, NULL, &error_abort);
bdrv_drained_end(bs);
bdrv_unref(bs);
}