/* * 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 * * 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 . */ #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) { 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); 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); if (!top) { return NULL; } top->total_sectors = source->total_sectors; top->opaque = state = g_new0(BDRVBackupTopState, 1); 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 append_failed; } /* * 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 failed_after_append; } 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 failed_after_append; } *bcs = state->bcs; bdrv_drained_end(source); return top; failed_after_append: state->active = false; bdrv_backup_top_drop(top); append_failed: bdrv_drained_end(source); bdrv_unref_child(top, state->target); bdrv_unref(top); error_propagate(errp, local_err); return NULL; } void bdrv_backup_top_drop(BlockDriverState *bs) { BDRVBackupTopState *s = bs->opaque; AioContext *aio_context = bdrv_get_aio_context(bs); aio_context_acquire(aio_context); 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); aio_context_release(aio_context); }