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xemu/block/commit.c
Kevin Wolf bde70715b6 commit: Remove overlay_bs 
We don't need to make any assumptions about the graph layout above the
top node of the commit operation any more. Remove the use of
bdrv_find_overlay() and related variables from the commit job code.

bdrv_drop_intermediate() doesn't use the 'active' parameter any more, so
we can just drop it.

The overlay node was previously added to the block job to get a
BLK_PERM_GRAPH_MOD. We really need to respect those permissions in
bdrv_drop_intermediate() now, but as long as we haven't figured out yet
how BLK_PERM_GRAPH_MOD is actually supposed to work, just leave a TODO
comment there.

With this change, it is now possible to perform another block job on an
overlay node without conflicts. qemu-iotests 030 is changed accordingly.

Signed-off-by: Kevin Wolf <kwolf@redhat.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
2017-10-06 16:28:58 +02:00

553 lines
16 KiB
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/*
* 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 */
};
#define SLICE_TIME 100000000ULL /* ns */
typedef struct CommitBlockJob {
BlockJob common;
RateLimit limit;
BlockDriverState *commit_top_bs;
BlockBackend *top;
BlockBackend *base;
BlockdevOnError on_error;
int base_flags;
char *backing_file_str;
} CommitBlockJob;
static int coroutine_fn commit_populate(BlockBackend *bs, BlockBackend *base,
int64_t offset, uint64_t bytes,
void *buf)
{
int ret = 0;
QEMUIOVector qiov;
struct iovec iov = {
.iov_base = buf,
.iov_len = bytes,
};
assert(bytes < SIZE_MAX);
qemu_iovec_init_external(&qiov, &iov, 1);
ret = blk_co_preadv(bs, offset, qiov.size, &qiov, 0);
if (ret < 0) {
return ret;
}
ret = blk_co_pwritev(base, offset, qiov.size, &qiov, 0);
if (ret < 0) {
return ret;
}
return 0;
}
typedef struct {
int ret;
} CommitCompleteData;
static void commit_complete(BlockJob *job, void *opaque)
{
CommitBlockJob *s = container_of(job, CommitBlockJob, common);
CommitCompleteData *data = opaque;
BlockDriverState *top = blk_bs(s->top);
BlockDriverState *base = blk_bs(s->base);
BlockDriverState *commit_top_bs = s->commit_top_bs;
int ret = data->ret;
bool remove_commit_top_bs = false;
/* Make sure commit_top_bs and top stay around until bdrv_replace_node() */
bdrv_ref(top);
bdrv_ref(commit_top_bs);
/* Remove base node parent that still uses BLK_PERM_WRITE/RESIZE before
* the normal backing chain can be restored. */
blk_unref(s->base);
if (!block_job_is_cancelled(&s->common) && ret == 0) {
/* success */
ret = bdrv_drop_intermediate(s->commit_top_bs, base,
s->backing_file_str);
} else {
/* 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. */
remove_commit_top_bs = true;
}
/* 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_flags != bdrv_get_flags(base)) {
bdrv_reopen(base, s->base_flags, NULL);
}
g_free(s->backing_file_str);
blk_unref(s->top);
/* If there is more than one reference to the job (e.g. if called from
* block_job_finish_sync()), block_job_completed() won't free it and
* therefore the blockers on the intermediate nodes remain. This would
* cause bdrv_set_backing_hd() to fail. */
block_job_remove_all_bdrv(job);
block_job_completed(&s->common, ret);
g_free(data);
/* If bdrv_drop_intermediate() didn't already do that, remove the commit
* filter driver from the backing chain. Do this as the final step so that
* the 'consistent read' permission can be granted. */
if (remove_commit_top_bs) {
bdrv_child_try_set_perm(commit_top_bs->backing, 0, BLK_PERM_ALL,
&error_abort);
bdrv_replace_node(commit_top_bs, backing_bs(commit_top_bs),
&error_abort);
}
bdrv_unref(commit_top_bs);
bdrv_unref(top);
}
static void coroutine_fn commit_run(void *opaque)
{
CommitBlockJob *s = opaque;
CommitCompleteData *data;
int64_t offset;
uint64_t delay_ns = 0;
int ret = 0;
int64_t n = 0; /* bytes */
void *buf = NULL;
int bytes_written = 0;
int64_t base_len;
ret = s->common.len = blk_getlength(s->top);
if (s->common.len < 0) {
goto out;
}
ret = base_len = blk_getlength(s->base);
if (base_len < 0) {
goto out;
}
if (base_len < s->common.len) {
ret = blk_truncate(s->base, s->common.len, PREALLOC_MODE_OFF, NULL);
if (ret) {
goto out;
}
}
buf = blk_blockalign(s->top, COMMIT_BUFFER_SIZE);
for (offset = 0; offset < s->common.len; offset += n) {
bool copy;
/* 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_sleep_ns(&s->common, QEMU_CLOCK_REALTIME, delay_ns);
if (block_job_is_cancelled(&s->common)) {
break;
}
/* Copy if allocated above the base */
ret = bdrv_is_allocated_above(blk_bs(s->top), blk_bs(s->base),
offset, COMMIT_BUFFER_SIZE, &n);
copy = (ret == 1);
trace_commit_one_iteration(s, offset, n, ret);
if (copy) {
ret = commit_populate(s->top, s->base, offset, n, buf);
bytes_written += n;
}
if (ret < 0) {
BlockErrorAction action =
block_job_error_action(&s->common, false, s->on_error, -ret);
if (action == BLOCK_ERROR_ACTION_REPORT) {
goto out;
} else {
n = 0;
continue;
}
}
/* Publish progress */
s->common.offset += n;
if (copy && s->common.speed) {
delay_ns = ratelimit_calculate_delay(&s->limit, n);
}
}
ret = 0;
out:
qemu_vfree(buf);
data = g_malloc(sizeof(*data));
data->ret = ret;
block_job_defer_to_main_loop(&s->common, commit_complete, data);
}
static void commit_set_speed(BlockJob *job, int64_t speed, Error **errp)
{
CommitBlockJob *s = container_of(job, CommitBlockJob, common);
if (speed < 0) {
error_setg(errp, QERR_INVALID_PARAMETER, "speed");
return;
}
ratelimit_set_speed(&s->limit, speed, SLICE_TIME);
}
static const BlockJobDriver commit_job_driver = {
.instance_size = sizeof(CommitBlockJob),
.job_type = BLOCK_JOB_TYPE_COMMIT,
.set_speed = commit_set_speed,
.start = commit_run,
};
static int coroutine_fn bdrv_commit_top_preadv(BlockDriverState *bs,
uint64_t offset, uint64_t bytes, QEMUIOVector *qiov, int flags)
{
return bdrv_co_preadv(bs->backing, offset, bytes, qiov, flags);
}
static void bdrv_commit_top_refresh_filename(BlockDriverState *bs, QDict *opts)
{
bdrv_refresh_filename(bs->backing->bs);
pstrcpy(bs->exact_filename, sizeof(bs->exact_filename),
bs->backing->bs->filename);
}
static void bdrv_commit_top_close(BlockDriverState *bs)
{
}
static void bdrv_commit_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)
{
*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_co_get_block_status = bdrv_co_get_block_status_from_backing,
.bdrv_refresh_filename = bdrv_commit_top_refresh_filename,
.bdrv_close = bdrv_commit_top_close,
.bdrv_child_perm = bdrv_commit_top_child_perm,
};
void commit_start(const char *job_id, BlockDriverState *bs,
BlockDriverState *base, BlockDriverState *top, int64_t speed,
BlockdevOnError on_error, const char *backing_file_str,
const char *filter_node_name, Error **errp)
{
CommitBlockJob *s;
BlockReopenQueue *reopen_queue = NULL;
int orig_base_flags;
BlockDriverState *iter;
BlockDriverState *commit_top_bs = NULL;
Error *local_err = NULL;
int ret;
assert(top != bs);
if (top == base) {
error_setg(errp, "Invalid files for merge: top and base are the same");
return;
}
s = block_job_create(job_id, &commit_job_driver, bs, 0, BLK_PERM_ALL,
speed, BLOCK_JOB_DEFAULT, NULL, NULL, errp);
if (!s) {
return;
}
/* convert base to r/w, if necessary */
orig_base_flags = bdrv_get_flags(base);
if (!(orig_base_flags & BDRV_O_RDWR)) {
reopen_queue = bdrv_reopen_queue(reopen_queue, base, NULL,
orig_base_flags | BDRV_O_RDWR);
}
if (reopen_queue) {
bdrv_reopen_multiple(bdrv_get_aio_context(bs), reopen_queue, &local_err);
if (local_err != NULL) {
error_propagate(errp, local_err);
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;
}
commit_top_bs->total_sectors = top->total_sectors;
bdrv_set_aio_context(commit_top_bs, bdrv_get_aio_context(top));
bdrv_set_backing_hd(commit_top_bs, top, &local_err);
if (local_err) {
bdrv_unref(commit_top_bs);
commit_top_bs = NULL;
error_propagate(errp, local_err);
goto fail;
}
bdrv_replace_node(top, commit_top_bs, &local_err);
if (local_err) {
bdrv_unref(commit_top_bs);
commit_top_bs = NULL;
error_propagate(errp, local_err);
goto fail;
}
s->commit_top_bs = commit_top_bs;
bdrv_unref(commit_top_bs);
/* Block all nodes between top and base, because they will
* disappear from the chain after this operation. */
assert(bdrv_chain_contains(top, base));
for (iter = top; iter != base; iter = backing_bs(iter)) {
/* 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. */
ret = block_job_add_bdrv(&s->common, "intermediate node", iter, 0,
BLK_PERM_WRITE_UNCHANGED | BLK_PERM_WRITE,
errp);
if (ret < 0) {
goto fail;
}
}
ret = block_job_add_bdrv(&s->common, "base", base, 0, BLK_PERM_ALL, errp);
if (ret < 0) {
goto fail;
}
s->base = blk_new(BLK_PERM_CONSISTENT_READ
| BLK_PERM_WRITE
| BLK_PERM_RESIZE,
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;
}
/* Required permissions are already taken with block_job_add_bdrv() */
s->top = blk_new(0, BLK_PERM_ALL);
ret = blk_insert_bs(s->top, top, errp);
if (ret < 0) {
goto fail;
}
s->base_flags = orig_base_flags;
s->backing_file_str = g_strdup(backing_file_str);
s->on_error = on_error;
trace_commit_start(bs, base, top, s);
block_job_start(&s->common);
return;
fail:
if (s->base) {
blk_unref(s->base);
}
if (s->top) {
blk_unref(s->top);
}
if (commit_top_bs) {
bdrv_replace_node(commit_top_bs, top, &error_abort);
}
block_job_early_fail(&s->common);
}
#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;
int64_t offset, length, backing_length;
int ro, open_flags;
int64_t n;
int ret = 0;
uint8_t *buf = NULL;
Error *local_err = NULL;
if (!drv)
return -ENOMEDIUM;
if (!bs->backing) {
return -ENOTSUP;
}
if (bdrv_op_is_blocked(bs, BLOCK_OP_TYPE_COMMIT_SOURCE, NULL) ||
bdrv_op_is_blocked(bs->backing->bs, BLOCK_OP_TYPE_COMMIT_TARGET, NULL)) {
return -EBUSY;
}
ro = bs->backing->bs->read_only;
open_flags = bs->backing->bs->open_flags;
if (ro) {
if (bdrv_reopen(bs->backing->bs, open_flags | BDRV_O_RDWR, NULL)) {
return -EACCES;
}
}
src = blk_new(BLK_PERM_CONSISTENT_READ, BLK_PERM_ALL);
backing = blk_new(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 */
backing_file_bs = backing_bs(bs);
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_aio_context(commit_top_bs, bdrv_get_aio_context(backing_file_bs));
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, PREALLOC_MODE_OFF, &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;
}
}
}
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;
}
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