Backup-top filter caches write operations and does copy-before-write operations.
The driver will be used in backup instead of write-notifiers. Signed-off-by: Vladimir Sementsov-Ogievskiy <vsement...@virtuozzo.com> --- block/backup-top.h | 37 +++++++ block/backup-top.c | 245 ++++++++++++++++++++++++++++++++++++++++++++ block/Makefile.objs | 2 + 3 files changed, 284 insertions(+) create mode 100644 block/backup-top.h create mode 100644 block/backup-top.c diff --git a/block/backup-top.h b/block/backup-top.h new file mode 100644 index 0000000000..67de7a9133 --- /dev/null +++ b/block/backup-top.h @@ -0,0 +1,37 @@ +/* + * 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 <vsement...@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 BACKUP_TOP_H +#define BACKUP_TOP_H + +#include "block/block_int.h" + +BlockDriverState *bdrv_backup_top_append(BlockDriverState *source, + const char *filter_node_name, + Error **errp); +void bdrv_backup_top_set_bcs(BlockDriverState *bs, BlockCopyState *copy_state); +void bdrv_backup_top_drop(BlockDriverState *bs); + +#endif /* BACKUP_TOP_H */ diff --git a/block/backup-top.c b/block/backup-top.c new file mode 100644 index 0000000000..41cb015452 --- /dev/null +++ b/block/backup-top.c @@ -0,0 +1,245 @@ +/* + * 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 <vsement...@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; + 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) +{ + /* + * Here we'd like to use block_copy(), but it needs some additional + * synchronization mechanism to prevent intersecting guest writes during + * copy operation. The will appear in further commit (it should be done + * together with moving backup to using of backup-top and to the same + * synchronization mechanism), and for now it is a TODO. + */ + + abort(); +} + +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; + } + bdrv_refresh_filename(bs->backing->bs); + 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; + } + + bdrv_filter_default_perms(bs, c, role, reopen_queue, perm, shared, + nperm, nshared); + + *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, + const char *filter_node_name, + 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); + + if (!top) { + return NULL; + } + + top->total_sectors = source->total_sectors; + top->opaque = state = g_new0(BDRVBackupTopState, 1); + + 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: "); + } else { + /* + * 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) { + state->active = false; + bdrv_backup_top_drop(top); + error_prepend(&local_err, + "Cannot set permissions for backup-top filter: "); + } + } + + bdrv_drained_end(source); + + if (local_err) { + bdrv_unref(top); + error_propagate(errp, local_err); + return NULL; + } + + assert(!(top->backing->shared_perm & BLK_PERM_WRITE)); + + return top; +} + +void bdrv_backup_top_set_bcs(BlockDriverState *bs, BlockCopyState *copy_state) +{ + BDRVBackupTopState *s = bs->opaque; + + assert(blk_bs(copy_state->source) == bs->backing->bs); + s->bcs = copy_state; +} + +void bdrv_backup_top_drop(BlockDriverState *bs) +{ + AioContext *aio_context = bdrv_get_aio_context(bs); + + aio_context_acquire(aio_context); + + bdrv_drained_begin(bs); + + bdrv_child_try_set_perm(bs->backing, 0, BLK_PERM_ALL, &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); + + aio_context_release(aio_context); +} diff --git a/block/Makefile.objs b/block/Makefile.objs index 0b5c635fb2..6f348c56c9 100644 --- a/block/Makefile.objs +++ b/block/Makefile.objs @@ -41,6 +41,8 @@ block-obj-y += block-copy.o block-obj-y += crypto.o +block-obj-y += backup-top.o + common-obj-y += stream.o nfs.o-libs := $(LIBNFS_LIBS) -- 2.18.0
