/* * Live block commit * * Copyright Red Hat, Inc. 2012 * * Authors: * Jeff Cody * Based on stream.c by Stefan Hajnoczi * * This work is licensed under the terms of the GNU LGPL, version 2 or later. * See the COPYING.LIB file in the top-level directory. * */ #include "qemu/osdep.h" #include "qemu/cutils.h" #include "trace.h" #include "block/block_int.h" #include "block/blockjob_int.h" #include "qapi/error.h" #include "qemu/ratelimit.h" #include "qemu/memalign.h" #include "sysemu/block-backend.h" enum { /* * Size of data buffer for populating the image file. This should be large * enough to process multiple clusters in a single call, so that populating * contiguous regions of the image is efficient. */ COMMIT_BUFFER_SIZE = 512 * 1024, /* in bytes */ }; typedef struct CommitBlockJob { BlockJob common; BlockDriverState *commit_top_bs; BlockBackend *top; BlockBackend *base; BlockDriverState *base_bs; BlockDriverState *base_overlay; BlockdevOnError on_error; bool base_read_only; bool chain_frozen; char *backing_file_str; } CommitBlockJob; static int commit_prepare(Job *job) { CommitBlockJob *s = container_of(job, CommitBlockJob, common.job); bdrv_graph_rdlock_main_loop(); bdrv_unfreeze_backing_chain(s->commit_top_bs, s->base_bs); s->chain_frozen = false; bdrv_graph_rdunlock_main_loop(); /* Remove base node parent that still uses BLK_PERM_WRITE/RESIZE before * the normal backing chain can be restored. */ blk_unref(s->base); s->base = NULL; /* FIXME: bdrv_drop_intermediate treats total failures and partial failures * identically. Further work is needed to disambiguate these cases. */ return bdrv_drop_intermediate(s->commit_top_bs, s->base_bs, s->backing_file_str); } static void commit_abort(Job *job) { CommitBlockJob *s = container_of(job, CommitBlockJob, common.job); BlockDriverState *top_bs = blk_bs(s->top); BlockDriverState *commit_top_backing_bs; if (s->chain_frozen) { bdrv_graph_rdlock_main_loop(); bdrv_unfreeze_backing_chain(s->commit_top_bs, s->base_bs); bdrv_graph_rdunlock_main_loop(); } /* Make sure commit_top_bs and top stay around until bdrv_replace_node() */ bdrv_ref(top_bs); bdrv_ref(s->commit_top_bs); if (s->base) { blk_unref(s->base); } /* free the blockers on the intermediate nodes so that bdrv_replace_nodes * can succeed */ block_job_remove_all_bdrv(&s->common); /* If bdrv_drop_intermediate() failed (or was not invoked), remove the * commit filter driver from the backing chain now. Do this as the final * step so that the 'consistent read' permission can be granted. * * XXX Can (or should) we somehow keep 'consistent read' blocked even * after the failed/cancelled commit job is gone? If we already wrote * something to base, the intermediate images aren't valid any more. */ bdrv_graph_rdlock_main_loop(); commit_top_backing_bs = s->commit_top_bs->backing->bs; bdrv_graph_rdunlock_main_loop(); bdrv_drained_begin(commit_top_backing_bs); bdrv_graph_wrlock(commit_top_backing_bs); bdrv_replace_node(s->commit_top_bs, commit_top_backing_bs, &error_abort); bdrv_graph_wrunlock(commit_top_backing_bs); bdrv_drained_end(commit_top_backing_bs); bdrv_unref(s->commit_top_bs); bdrv_unref(top_bs); } static void commit_clean(Job *job) { CommitBlockJob *s = container_of(job, CommitBlockJob, common.job); /* restore base open flags here if appropriate (e.g., change the base back * to r/o). These reopens do not need to be atomic, since we won't abort * even on failure here */ if (s->base_read_only) { bdrv_reopen_set_read_only(s->base_bs, true, NULL); } g_free(s->backing_file_str); blk_unref(s->top); } static int coroutine_fn commit_run(Job *job, Error **errp) { CommitBlockJob *s = container_of(job, CommitBlockJob, common.job); int64_t offset; int ret = 0; int64_t n = 0; /* bytes */ QEMU_AUTO_VFREE void *buf = NULL; int64_t len, base_len; len = blk_co_getlength(s->top); if (len < 0) { return len; } job_progress_set_remaining(&s->common.job, len); base_len = blk_co_getlength(s->base); if (base_len < 0) { return base_len; } if (base_len < len) { ret = blk_co_truncate(s->base, len, false, PREALLOC_MODE_OFF, 0, NULL); if (ret) { return ret; } } buf = blk_blockalign(s->top, COMMIT_BUFFER_SIZE); for (offset = 0; offset < len; offset += n) { bool copy; bool error_in_source = true; /* Note that even when no rate limit is applied we need to yield * with no pending I/O here so that bdrv_drain_all() returns. */ block_job_ratelimit_sleep(&s->common); if (job_is_cancelled(&s->common.job)) { break; } /* Copy if allocated above the base */ ret = blk_co_is_allocated_above(s->top, s->base_overlay, true, offset, COMMIT_BUFFER_SIZE, &n); copy = (ret > 0); trace_commit_one_iteration(s, offset, n, ret); if (copy) { assert(n < SIZE_MAX); ret = blk_co_pread(s->top, offset, n, buf, 0); if (ret >= 0) { ret = blk_co_pwrite(s->base, offset, n, buf, 0); if (ret < 0) { error_in_source = false; } } } if (ret < 0) { BlockErrorAction action = block_job_error_action(&s->common, s->on_error, error_in_source, -ret); if (action == BLOCK_ERROR_ACTION_REPORT) { return ret; } else { n = 0; continue; } } /* Publish progress */ job_progress_update(&s->common.job, n); if (copy) { block_job_ratelimit_processed_bytes(&s->common, n); } } return 0; } static const BlockJobDriver commit_job_driver = { .job_driver = { .instance_size = sizeof(CommitBlockJob), .job_type = JOB_TYPE_COMMIT, .free = block_job_free, .user_resume = block_job_user_resume, .run = commit_run, .prepare = commit_prepare, .abort = commit_abort, .clean = commit_clean }, }; static int coroutine_fn GRAPH_RDLOCK bdrv_commit_top_preadv(BlockDriverState *bs, int64_t offset, int64_t bytes, QEMUIOVector *qiov, BdrvRequestFlags flags) { return bdrv_co_preadv(bs->backing, offset, bytes, qiov, flags); } static GRAPH_RDLOCK void bdrv_commit_top_refresh_filename(BlockDriverState *bs) { pstrcpy(bs->exact_filename, sizeof(bs->exact_filename), bs->backing->bs->filename); } static void bdrv_commit_top_child_perm(BlockDriverState *bs, BdrvChild *c, BdrvChildRole role, BlockReopenQueue *reopen_queue, uint64_t perm, uint64_t shared, uint64_t *nperm, uint64_t *nshared) { *nperm = 0; *nshared = BLK_PERM_ALL; } /* Dummy node that provides consistent read to its users without requiring it * from its backing file and that allows writes on the backing file chain. */ static BlockDriver bdrv_commit_top = { .format_name = "commit_top", .bdrv_co_preadv = bdrv_commit_top_preadv, .bdrv_refresh_filename = bdrv_commit_top_refresh_filename, .bdrv_child_perm = bdrv_commit_top_child_perm, .is_filter = true, .filtered_child_is_backing = true, }; void commit_start(const char *job_id, BlockDriverState *bs, BlockDriverState *base, BlockDriverState *top, int creation_flags, int64_t speed, BlockdevOnError on_error, const char *backing_file_str, const char *filter_node_name, Error **errp) { CommitBlockJob *s; BlockDriverState *iter; BlockDriverState *commit_top_bs = NULL; BlockDriverState *filtered_base; int64_t base_size, top_size; uint64_t base_perms, iter_shared_perms; int ret; GLOBAL_STATE_CODE(); assert(top != bs); bdrv_graph_rdlock_main_loop(); if (bdrv_skip_filters(top) == bdrv_skip_filters(base)) { error_setg(errp, "Invalid files for merge: top and base are the same"); bdrv_graph_rdunlock_main_loop(); return; } bdrv_graph_rdunlock_main_loop(); base_size = bdrv_getlength(base); if (base_size < 0) { error_setg_errno(errp, -base_size, "Could not inquire base image size"); return; } top_size = bdrv_getlength(top); if (top_size < 0) { error_setg_errno(errp, -top_size, "Could not inquire top image size"); return; } base_perms = BLK_PERM_CONSISTENT_READ | BLK_PERM_WRITE; if (base_size < top_size) { base_perms |= BLK_PERM_RESIZE; } s = block_job_create(job_id, &commit_job_driver, NULL, bs, 0, BLK_PERM_ALL, speed, creation_flags, NULL, NULL, errp); if (!s) { return; } /* convert base to r/w, if necessary */ s->base_read_only = bdrv_is_read_only(base); if (s->base_read_only) { if (bdrv_reopen_set_read_only(base, false, errp) != 0) { goto fail; } } /* Insert commit_top block node above top, so we can block consistent read * on the backing chain below it */ commit_top_bs = bdrv_new_open_driver(&bdrv_commit_top, filter_node_name, 0, errp); if (commit_top_bs == NULL) { goto fail; } if (!filter_node_name) { commit_top_bs->implicit = true; } /* So that we can always drop this node */ commit_top_bs->never_freeze = true; commit_top_bs->total_sectors = top->total_sectors; ret = bdrv_append(commit_top_bs, top, errp); bdrv_unref(commit_top_bs); /* referenced by new parents or failed */ if (ret < 0) { commit_top_bs = NULL; goto fail; } s->commit_top_bs = commit_top_bs; /* * Block all nodes between top and base, because they will * disappear from the chain after this operation. * Note that this assumes that the user is fine with removing all * nodes (including R/W filters) between top and base. Assuring * this is the responsibility of the interface (i.e. whoever calls * commit_start()). */ bdrv_graph_wrlock(top); s->base_overlay = bdrv_find_overlay(top, base); assert(s->base_overlay); /* * The topmost node with * bdrv_skip_filters(filtered_base) == bdrv_skip_filters(base) */ filtered_base = bdrv_cow_bs(s->base_overlay); assert(bdrv_skip_filters(filtered_base) == bdrv_skip_filters(base)); /* * XXX BLK_PERM_WRITE needs to be allowed so we don't block ourselves * at s->base (if writes are blocked for a node, they are also blocked * for its backing file). The other options would be a second filter * driver above s->base. */ iter_shared_perms = BLK_PERM_WRITE_UNCHANGED | BLK_PERM_WRITE; for (iter = top; iter != base; iter = bdrv_filter_or_cow_bs(iter)) { if (iter == filtered_base) { /* * From here on, all nodes are filters on the base. This * allows us to share BLK_PERM_CONSISTENT_READ. */ iter_shared_perms |= BLK_PERM_CONSISTENT_READ; } ret = block_job_add_bdrv(&s->common, "intermediate node", iter, 0, iter_shared_perms, errp); if (ret < 0) { bdrv_graph_wrunlock(top); goto fail; } } if (bdrv_freeze_backing_chain(commit_top_bs, base, errp) < 0) { bdrv_graph_wrunlock(top); goto fail; } s->chain_frozen = true; ret = block_job_add_bdrv(&s->common, "base", base, 0, BLK_PERM_ALL, errp); bdrv_graph_wrunlock(top); if (ret < 0) { goto fail; } s->base = blk_new(s->common.job.aio_context, base_perms, BLK_PERM_CONSISTENT_READ | BLK_PERM_WRITE_UNCHANGED); ret = blk_insert_bs(s->base, base, errp); if (ret < 0) { goto fail; } blk_set_disable_request_queuing(s->base, true); s->base_bs = base; /* Required permissions are already taken with block_job_add_bdrv() */ s->top = blk_new(s->common.job.aio_context, 0, BLK_PERM_ALL); ret = blk_insert_bs(s->top, top, errp); if (ret < 0) { goto fail; } blk_set_disable_request_queuing(s->top, true); s->backing_file_str = g_strdup(backing_file_str); s->on_error = on_error; trace_commit_start(bs, base, top, s); job_start(&s->common.job); return; fail: if (s->chain_frozen) { bdrv_graph_rdlock_main_loop(); bdrv_unfreeze_backing_chain(commit_top_bs, base); bdrv_graph_rdunlock_main_loop(); } if (s->base) { blk_unref(s->base); } if (s->top) { blk_unref(s->top); } if (s->base_read_only) { bdrv_reopen_set_read_only(base, true, NULL); } job_early_fail(&s->common.job); /* commit_top_bs has to be replaced after deleting the block job, * otherwise this would fail because of lack of permissions. */ if (commit_top_bs) { bdrv_drained_begin(top); bdrv_graph_wrlock(top); bdrv_replace_node(commit_top_bs, top, &error_abort); bdrv_graph_wrunlock(top); bdrv_drained_end(top); } } #define COMMIT_BUF_SIZE (2048 * BDRV_SECTOR_SIZE) /* commit COW file into the raw image */ int bdrv_commit(BlockDriverState *bs) { BlockBackend *src, *backing; BlockDriverState *backing_file_bs = NULL; BlockDriverState *commit_top_bs = NULL; BlockDriver *drv = bs->drv; AioContext *ctx; int64_t offset, length, backing_length; int ro; int64_t n; int ret = 0; QEMU_AUTO_VFREE uint8_t *buf = NULL; Error *local_err = NULL; GLOBAL_STATE_CODE(); GRAPH_RDLOCK_GUARD_MAINLOOP(); if (!drv) return -ENOMEDIUM; backing_file_bs = bdrv_cow_bs(bs); if (!backing_file_bs) { return -ENOTSUP; } if (bdrv_op_is_blocked(bs, BLOCK_OP_TYPE_COMMIT_SOURCE, NULL) || bdrv_op_is_blocked(backing_file_bs, BLOCK_OP_TYPE_COMMIT_TARGET, NULL)) { return -EBUSY; } ro = bdrv_is_read_only(backing_file_bs); if (ro) { if (bdrv_reopen_set_read_only(backing_file_bs, false, NULL)) { return -EACCES; } } ctx = bdrv_get_aio_context(bs); /* WRITE_UNCHANGED is required for bdrv_make_empty() */ src = blk_new(ctx, BLK_PERM_CONSISTENT_READ | BLK_PERM_WRITE_UNCHANGED, BLK_PERM_ALL); backing = blk_new(ctx, BLK_PERM_WRITE | BLK_PERM_RESIZE, BLK_PERM_ALL); ret = blk_insert_bs(src, bs, &local_err); if (ret < 0) { error_report_err(local_err); goto ro_cleanup; } /* Insert commit_top block node above backing, so we can write to it */ commit_top_bs = bdrv_new_open_driver(&bdrv_commit_top, NULL, BDRV_O_RDWR, &local_err); if (commit_top_bs == NULL) { error_report_err(local_err); goto ro_cleanup; } bdrv_set_backing_hd(commit_top_bs, backing_file_bs, &error_abort); bdrv_set_backing_hd(bs, commit_top_bs, &error_abort); ret = blk_insert_bs(backing, backing_file_bs, &local_err); if (ret < 0) { error_report_err(local_err); goto ro_cleanup; } length = blk_getlength(src); if (length < 0) { ret = length; goto ro_cleanup; } backing_length = blk_getlength(backing); if (backing_length < 0) { ret = backing_length; goto ro_cleanup; } /* If our top snapshot is larger than the backing file image, * grow the backing file image if possible. If not possible, * we must return an error */ if (length > backing_length) { ret = blk_truncate(backing, length, false, PREALLOC_MODE_OFF, 0, &local_err); if (ret < 0) { error_report_err(local_err); goto ro_cleanup; } } /* blk_try_blockalign() for src will choose an alignment that works for * backing as well, so no need to compare the alignment manually. */ buf = blk_try_blockalign(src, COMMIT_BUF_SIZE); if (buf == NULL) { ret = -ENOMEM; goto ro_cleanup; } for (offset = 0; offset < length; offset += n) { ret = bdrv_is_allocated(bs, offset, COMMIT_BUF_SIZE, &n); if (ret < 0) { goto ro_cleanup; } if (ret) { ret = blk_pread(src, offset, n, buf, 0); if (ret < 0) { goto ro_cleanup; } ret = blk_pwrite(backing, offset, n, buf, 0); if (ret < 0) { goto ro_cleanup; } } } ret = blk_make_empty(src, NULL); /* Ignore -ENOTSUP */ if (ret < 0 && ret != -ENOTSUP) { goto ro_cleanup; } blk_flush(src); /* * Make sure all data we wrote to the backing device is actually * stable on disk. */ blk_flush(backing); ret = 0; ro_cleanup: blk_unref(backing); if (bdrv_cow_bs(bs) != backing_file_bs) { bdrv_set_backing_hd(bs, backing_file_bs, &error_abort); } bdrv_unref(commit_top_bs); blk_unref(src); if (ro) { /* ignoring error return here */ bdrv_reopen_set_read_only(backing_file_bs, true, NULL); } return ret; }