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-rw-r--r--block/commit.c567
1 files changed, 567 insertions, 0 deletions
diff --git a/block/commit.c b/block/commit.c
new file mode 100644
index 000000000..10cc5ff45
--- /dev/null
+++ b/block/commit.c
@@ -0,0 +1,567 @@
+/*
+ * Live block commit
+ *
+ * Copyright Red Hat, Inc. 2012
+ *
+ * Authors:
+ * Jeff Cody <jcody@redhat.com>
+ * 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 "qapi/qmp/qerror.h"
+#include "qemu/ratelimit.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_unfreeze_backing_chain(s->commit_top_bs, s->base_bs);
+ s->chain_frozen = false;
+
+ /* 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);
+
+ if (s->chain_frozen) {
+ bdrv_unfreeze_backing_chain(s->commit_top_bs, s->base_bs);
+ }
+
+ /* 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_replace_node(s->commit_top_bs, s->commit_top_bs->backing->bs,
+ &error_abort);
+
+ 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;
+ uint64_t delay_ns = 0;
+ int ret = 0;
+ int64_t n = 0; /* bytes */
+ QEMU_AUTO_VFREE void *buf = NULL;
+ int64_t len, base_len;
+
+ len = blk_getlength(s->top);
+ if (len < 0) {
+ return len;
+ }
+ job_progress_set_remaining(&s->common.job, len);
+
+ base_len = blk_getlength(s->base);
+ if (base_len < 0) {
+ return base_len;
+ }
+
+ if (base_len < len) {
+ ret = blk_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.
+ */
+ job_sleep_ns(&s->common.job, delay_ns);
+ if (job_is_cancelled(&s->common.job)) {
+ break;
+ }
+ /* Copy if allocated above the base */
+ ret = bdrv_is_allocated_above(blk_bs(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) {
+ delay_ns = block_job_ratelimit_get_delay(&s->common, n);
+ } else {
+ delay_ns = 0;
+ }
+ }
+
+ 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 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 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,
+};
+
+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;
+
+ assert(top != bs);
+ if (bdrv_skip_filters(top) == bdrv_skip_filters(base)) {
+ error_setg(errp, "Invalid files for merge: top and base are the same");
+ return;
+ }
+
+ 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()).
+ */
+ 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) {
+ goto fail;
+ }
+ }
+
+ if (bdrv_freeze_backing_chain(commit_top_bs, base, errp) < 0) {
+ goto fail;
+ }
+ s->chain_frozen = true;
+
+ ret = block_job_add_bdrv(&s->common, "base", base, 0, BLK_PERM_ALL, errp);
+ if (ret < 0) {
+ goto fail;
+ }
+
+ s->base = blk_new(s->common.job.aio_context,
+ base_perms,
+ BLK_PERM_CONSISTENT_READ
+ | BLK_PERM_GRAPH_MOD
+ | 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_unfreeze_backing_chain(commit_top_bs, base);
+ }
+ 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_replace_node(commit_top_bs, top, &error_abort);
+ }
+}
+
+
+#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;
+
+ 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, buf, n);
+ if (ret < 0) {
+ goto ro_cleanup;
+ }
+
+ ret = blk_pwrite(backing, offset, buf, n, 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;
+}