qemu/block/commit.c
Stefan Hajnoczi 6bc30f1949 graph-lock: remove AioContext locking
Stop acquiring/releasing the AioContext lock in
bdrv_graph_wrlock()/bdrv_graph_unlock() since the lock no longer has any
effect.

The distinction between bdrv_graph_wrunlock() and
bdrv_graph_wrunlock_ctx() becomes meaningless and they can be collapsed
into one function.

Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
Reviewed-by: Kevin Wolf <kwolf@redhat.com>
Message-ID: <20231205182011.1976568-6-stefanha@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
2023-12-21 22:49:27 +01:00

597 lines
18 KiB
C

/*
* 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 "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();
bdrv_replace_node(s->commit_top_bs, commit_top_backing_bs, &error_abort);
bdrv_graph_wrunlock();
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();
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();
goto fail;
}
}
if (bdrv_freeze_backing_chain(commit_top_bs, base, errp) < 0) {
bdrv_graph_wrunlock();
goto fail;
}
s->chain_frozen = true;
ret = block_job_add_bdrv(&s->common, "base", base, 0, BLK_PERM_ALL, errp);
bdrv_graph_wrunlock();
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();
bdrv_replace_node(commit_top_bs, top, &error_abort);
bdrv_graph_wrunlock();
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;
}