535 lines
16 KiB
C
535 lines
16 KiB
C
/*
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* Live block commit
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*
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* Copyright Red Hat, Inc. 2012
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*
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* Authors:
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* Jeff Cody <jcody@redhat.com>
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* Based on stream.c by Stefan Hajnoczi
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*
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* This work is licensed under the terms of the GNU LGPL, version 2 or later.
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* See the COPYING.LIB file in the top-level directory.
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*
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*/
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#include "qemu/osdep.h"
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#include "qemu/cutils.h"
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#include "trace.h"
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#include "block/block_int.h"
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#include "block/blockjob_int.h"
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#include "qapi/error.h"
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#include "qapi/qmp/qerror.h"
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#include "qemu/ratelimit.h"
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#include "sysemu/block-backend.h"
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enum {
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/*
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* Size of data buffer for populating the image file. This should be large
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* enough to process multiple clusters in a single call, so that populating
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* contiguous regions of the image is efficient.
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*/
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COMMIT_BUFFER_SIZE = 512 * 1024, /* in bytes */
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};
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typedef struct CommitBlockJob {
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BlockJob common;
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BlockDriverState *commit_top_bs;
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BlockBackend *top;
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BlockBackend *base;
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BlockdevOnError on_error;
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int base_flags;
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char *backing_file_str;
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} CommitBlockJob;
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static int coroutine_fn commit_populate(BlockBackend *bs, BlockBackend *base,
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int64_t offset, uint64_t bytes,
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void *buf)
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{
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int ret = 0;
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QEMUIOVector qiov;
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struct iovec iov = {
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.iov_base = buf,
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.iov_len = bytes,
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};
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assert(bytes < SIZE_MAX);
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qemu_iovec_init_external(&qiov, &iov, 1);
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ret = blk_co_preadv(bs, offset, qiov.size, &qiov, 0);
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if (ret < 0) {
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return ret;
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}
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ret = blk_co_pwritev(base, offset, qiov.size, &qiov, 0);
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if (ret < 0) {
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return ret;
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}
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return 0;
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}
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typedef struct {
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int ret;
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} CommitCompleteData;
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static void commit_complete(Job *job, void *opaque)
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{
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CommitBlockJob *s = container_of(job, CommitBlockJob, common.job);
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BlockJob *bjob = &s->common;
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CommitCompleteData *data = opaque;
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BlockDriverState *top = blk_bs(s->top);
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BlockDriverState *base = blk_bs(s->base);
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BlockDriverState *commit_top_bs = s->commit_top_bs;
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int ret = data->ret;
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bool remove_commit_top_bs = false;
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/* Make sure commit_top_bs and top stay around until bdrv_replace_node() */
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bdrv_ref(top);
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bdrv_ref(commit_top_bs);
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/* Remove base node parent that still uses BLK_PERM_WRITE/RESIZE before
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* the normal backing chain can be restored. */
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blk_unref(s->base);
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if (!job_is_cancelled(job) && ret == 0) {
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/* success */
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ret = bdrv_drop_intermediate(s->commit_top_bs, base,
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s->backing_file_str);
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} else {
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/* XXX Can (or should) we somehow keep 'consistent read' blocked even
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* after the failed/cancelled commit job is gone? If we already wrote
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* something to base, the intermediate images aren't valid any more. */
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remove_commit_top_bs = true;
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}
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/* restore base open flags here if appropriate (e.g., change the base back
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* to r/o). These reopens do not need to be atomic, since we won't abort
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* even on failure here */
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if (s->base_flags != bdrv_get_flags(base)) {
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bdrv_reopen(base, s->base_flags, NULL);
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}
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g_free(s->backing_file_str);
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blk_unref(s->top);
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/* If there is more than one reference to the job (e.g. if called from
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* job_finish_sync()), job_completed() won't free it and therefore the
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* blockers on the intermediate nodes remain. This would cause
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* bdrv_set_backing_hd() to fail. */
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block_job_remove_all_bdrv(bjob);
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job_completed(job, ret, NULL);
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g_free(data);
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/* If bdrv_drop_intermediate() didn't already do that, remove the commit
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* filter driver from the backing chain. Do this as the final step so that
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* the 'consistent read' permission can be granted. */
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if (remove_commit_top_bs) {
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bdrv_child_try_set_perm(commit_top_bs->backing, 0, BLK_PERM_ALL,
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&error_abort);
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bdrv_replace_node(commit_top_bs, backing_bs(commit_top_bs),
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&error_abort);
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}
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bdrv_unref(commit_top_bs);
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bdrv_unref(top);
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}
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static void coroutine_fn commit_run(void *opaque)
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{
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CommitBlockJob *s = opaque;
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CommitCompleteData *data;
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int64_t offset;
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uint64_t delay_ns = 0;
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int ret = 0;
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int64_t n = 0; /* bytes */
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void *buf = NULL;
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int bytes_written = 0;
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int64_t len, base_len;
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ret = len = blk_getlength(s->top);
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if (len < 0) {
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goto out;
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}
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job_progress_set_remaining(&s->common.job, len);
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ret = base_len = blk_getlength(s->base);
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if (base_len < 0) {
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goto out;
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}
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if (base_len < len) {
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ret = blk_truncate(s->base, len, PREALLOC_MODE_OFF, NULL);
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if (ret) {
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goto out;
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}
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}
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buf = blk_blockalign(s->top, COMMIT_BUFFER_SIZE);
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for (offset = 0; offset < len; offset += n) {
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bool copy;
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/* Note that even when no rate limit is applied we need to yield
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* with no pending I/O here so that bdrv_drain_all() returns.
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*/
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job_sleep_ns(&s->common.job, delay_ns);
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if (job_is_cancelled(&s->common.job)) {
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break;
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}
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/* Copy if allocated above the base */
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ret = bdrv_is_allocated_above(blk_bs(s->top), blk_bs(s->base),
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offset, COMMIT_BUFFER_SIZE, &n);
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copy = (ret == 1);
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trace_commit_one_iteration(s, offset, n, ret);
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if (copy) {
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ret = commit_populate(s->top, s->base, offset, n, buf);
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bytes_written += n;
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}
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if (ret < 0) {
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BlockErrorAction action =
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block_job_error_action(&s->common, false, s->on_error, -ret);
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if (action == BLOCK_ERROR_ACTION_REPORT) {
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goto out;
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} else {
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n = 0;
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continue;
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}
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}
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/* Publish progress */
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job_progress_update(&s->common.job, n);
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if (copy) {
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delay_ns = block_job_ratelimit_get_delay(&s->common, n);
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} else {
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delay_ns = 0;
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}
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}
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ret = 0;
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out:
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qemu_vfree(buf);
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data = g_malloc(sizeof(*data));
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data->ret = ret;
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job_defer_to_main_loop(&s->common.job, commit_complete, data);
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}
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static const BlockJobDriver commit_job_driver = {
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.job_driver = {
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.instance_size = sizeof(CommitBlockJob),
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.job_type = JOB_TYPE_COMMIT,
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.free = block_job_free,
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.user_resume = block_job_user_resume,
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.drain = block_job_drain,
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.start = commit_run,
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},
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};
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static int coroutine_fn bdrv_commit_top_preadv(BlockDriverState *bs,
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uint64_t offset, uint64_t bytes, QEMUIOVector *qiov, int flags)
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{
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return bdrv_co_preadv(bs->backing, offset, bytes, qiov, flags);
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}
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static void bdrv_commit_top_refresh_filename(BlockDriverState *bs, QDict *opts)
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{
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bdrv_refresh_filename(bs->backing->bs);
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pstrcpy(bs->exact_filename, sizeof(bs->exact_filename),
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bs->backing->bs->filename);
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}
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static void bdrv_commit_top_child_perm(BlockDriverState *bs, BdrvChild *c,
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const BdrvChildRole *role,
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BlockReopenQueue *reopen_queue,
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uint64_t perm, uint64_t shared,
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uint64_t *nperm, uint64_t *nshared)
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{
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*nperm = 0;
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*nshared = BLK_PERM_ALL;
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}
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/* Dummy node that provides consistent read to its users without requiring it
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* from its backing file and that allows writes on the backing file chain. */
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static BlockDriver bdrv_commit_top = {
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.format_name = "commit_top",
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.bdrv_co_preadv = bdrv_commit_top_preadv,
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.bdrv_co_block_status = bdrv_co_block_status_from_backing,
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.bdrv_refresh_filename = bdrv_commit_top_refresh_filename,
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.bdrv_child_perm = bdrv_commit_top_child_perm,
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};
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void commit_start(const char *job_id, BlockDriverState *bs,
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BlockDriverState *base, BlockDriverState *top, int64_t speed,
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BlockdevOnError on_error, const char *backing_file_str,
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const char *filter_node_name, Error **errp)
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{
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CommitBlockJob *s;
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int orig_base_flags;
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BlockDriverState *iter;
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BlockDriverState *commit_top_bs = NULL;
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Error *local_err = NULL;
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int ret;
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assert(top != bs);
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if (top == base) {
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error_setg(errp, "Invalid files for merge: top and base are the same");
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return;
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}
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s = block_job_create(job_id, &commit_job_driver, NULL, bs, 0, BLK_PERM_ALL,
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speed, JOB_DEFAULT, NULL, NULL, errp);
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if (!s) {
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return;
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}
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/* convert base to r/w, if necessary */
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orig_base_flags = bdrv_get_flags(base);
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if (!(orig_base_flags & BDRV_O_RDWR)) {
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bdrv_reopen(base, orig_base_flags | BDRV_O_RDWR, &local_err);
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if (local_err != NULL) {
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error_propagate(errp, local_err);
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goto fail;
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}
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}
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/* Insert commit_top block node above top, so we can block consistent read
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* on the backing chain below it */
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commit_top_bs = bdrv_new_open_driver(&bdrv_commit_top, filter_node_name, 0,
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errp);
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if (commit_top_bs == NULL) {
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goto fail;
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}
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if (!filter_node_name) {
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commit_top_bs->implicit = true;
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}
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commit_top_bs->total_sectors = top->total_sectors;
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bdrv_set_aio_context(commit_top_bs, bdrv_get_aio_context(top));
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bdrv_set_backing_hd(commit_top_bs, top, &local_err);
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if (local_err) {
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bdrv_unref(commit_top_bs);
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commit_top_bs = NULL;
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error_propagate(errp, local_err);
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goto fail;
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}
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bdrv_replace_node(top, commit_top_bs, &local_err);
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if (local_err) {
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bdrv_unref(commit_top_bs);
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commit_top_bs = NULL;
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error_propagate(errp, local_err);
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goto fail;
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}
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s->commit_top_bs = commit_top_bs;
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bdrv_unref(commit_top_bs);
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/* Block all nodes between top and base, because they will
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* disappear from the chain after this operation. */
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assert(bdrv_chain_contains(top, base));
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for (iter = top; iter != base; iter = backing_bs(iter)) {
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/* XXX BLK_PERM_WRITE needs to be allowed so we don't block ourselves
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* at s->base (if writes are blocked for a node, they are also blocked
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* for its backing file). The other options would be a second filter
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* driver above s->base. */
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ret = block_job_add_bdrv(&s->common, "intermediate node", iter, 0,
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BLK_PERM_WRITE_UNCHANGED | BLK_PERM_WRITE,
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errp);
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if (ret < 0) {
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goto fail;
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}
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}
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ret = block_job_add_bdrv(&s->common, "base", base, 0, BLK_PERM_ALL, errp);
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if (ret < 0) {
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goto fail;
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}
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s->base = blk_new(BLK_PERM_CONSISTENT_READ
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| BLK_PERM_WRITE
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| BLK_PERM_RESIZE,
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BLK_PERM_CONSISTENT_READ
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| BLK_PERM_GRAPH_MOD
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| BLK_PERM_WRITE_UNCHANGED);
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ret = blk_insert_bs(s->base, base, errp);
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if (ret < 0) {
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goto fail;
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}
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/* Required permissions are already taken with block_job_add_bdrv() */
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s->top = blk_new(0, BLK_PERM_ALL);
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ret = blk_insert_bs(s->top, top, errp);
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if (ret < 0) {
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goto fail;
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}
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s->base_flags = orig_base_flags;
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s->backing_file_str = g_strdup(backing_file_str);
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s->on_error = on_error;
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trace_commit_start(bs, base, top, s);
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job_start(&s->common.job);
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return;
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fail:
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if (s->base) {
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blk_unref(s->base);
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}
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if (s->top) {
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blk_unref(s->top);
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}
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if (commit_top_bs) {
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bdrv_replace_node(commit_top_bs, top, &error_abort);
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}
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job_early_fail(&s->common.job);
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}
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#define COMMIT_BUF_SIZE (2048 * BDRV_SECTOR_SIZE)
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/* commit COW file into the raw image */
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int bdrv_commit(BlockDriverState *bs)
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{
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BlockBackend *src, *backing;
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BlockDriverState *backing_file_bs = NULL;
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BlockDriverState *commit_top_bs = NULL;
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BlockDriver *drv = bs->drv;
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int64_t offset, length, backing_length;
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int ro, open_flags;
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int64_t n;
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int ret = 0;
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uint8_t *buf = NULL;
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Error *local_err = NULL;
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if (!drv)
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return -ENOMEDIUM;
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if (!bs->backing) {
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return -ENOTSUP;
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}
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if (bdrv_op_is_blocked(bs, BLOCK_OP_TYPE_COMMIT_SOURCE, NULL) ||
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bdrv_op_is_blocked(bs->backing->bs, BLOCK_OP_TYPE_COMMIT_TARGET, NULL)) {
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return -EBUSY;
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}
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ro = bs->backing->bs->read_only;
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open_flags = bs->backing->bs->open_flags;
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if (ro) {
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if (bdrv_reopen(bs->backing->bs, open_flags | BDRV_O_RDWR, NULL)) {
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return -EACCES;
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}
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}
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src = blk_new(BLK_PERM_CONSISTENT_READ, BLK_PERM_ALL);
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backing = blk_new(BLK_PERM_WRITE | BLK_PERM_RESIZE, BLK_PERM_ALL);
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ret = blk_insert_bs(src, bs, &local_err);
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if (ret < 0) {
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error_report_err(local_err);
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goto ro_cleanup;
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}
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/* Insert commit_top block node above backing, so we can write to it */
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backing_file_bs = backing_bs(bs);
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commit_top_bs = bdrv_new_open_driver(&bdrv_commit_top, NULL, BDRV_O_RDWR,
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&local_err);
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if (commit_top_bs == NULL) {
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error_report_err(local_err);
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goto ro_cleanup;
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}
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bdrv_set_aio_context(commit_top_bs, bdrv_get_aio_context(backing_file_bs));
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bdrv_set_backing_hd(commit_top_bs, backing_file_bs, &error_abort);
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bdrv_set_backing_hd(bs, commit_top_bs, &error_abort);
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ret = blk_insert_bs(backing, backing_file_bs, &local_err);
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if (ret < 0) {
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error_report_err(local_err);
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goto ro_cleanup;
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}
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length = blk_getlength(src);
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if (length < 0) {
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ret = length;
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goto ro_cleanup;
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}
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backing_length = blk_getlength(backing);
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if (backing_length < 0) {
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ret = backing_length;
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goto ro_cleanup;
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}
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/* If our top snapshot is larger than the backing file image,
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* grow the backing file image if possible. If not possible,
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* we must return an error */
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if (length > backing_length) {
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ret = blk_truncate(backing, length, PREALLOC_MODE_OFF, &local_err);
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if (ret < 0) {
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error_report_err(local_err);
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goto ro_cleanup;
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}
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}
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/* blk_try_blockalign() for src will choose an alignment that works for
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* backing as well, so no need to compare the alignment manually. */
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buf = blk_try_blockalign(src, COMMIT_BUF_SIZE);
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if (buf == NULL) {
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ret = -ENOMEM;
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goto ro_cleanup;
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}
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for (offset = 0; offset < length; offset += n) {
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ret = bdrv_is_allocated(bs, offset, COMMIT_BUF_SIZE, &n);
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if (ret < 0) {
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goto ro_cleanup;
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}
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if (ret) {
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ret = blk_pread(src, offset, buf, n);
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if (ret < 0) {
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goto ro_cleanup;
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}
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ret = blk_pwrite(backing, offset, buf, n, 0);
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if (ret < 0) {
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goto ro_cleanup;
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}
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}
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}
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|
|
if (drv->bdrv_make_empty) {
|
|
ret = drv->bdrv_make_empty(bs);
|
|
if (ret < 0) {
|
|
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:
|
|
qemu_vfree(buf);
|
|
|
|
blk_unref(backing);
|
|
if (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(bs->backing->bs, open_flags & ~BDRV_O_RDWR, NULL);
|
|
}
|
|
|
|
return ret;
|
|
}
|