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block: remove AioContext locking

Browse source 
This is the big patch that removes
aio_context_acquire()/aio_context_release() from the block layer and
affected block layer users.

There isn't a clean way to split this patch and the reviewers are likely
the same group of people, so I decided to do it in one patch.

Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
Reviewed-by: Kevin Wolf <kwolf@redhat.com>
Reviewed-by: Paul Durrant <paul@xen.org>
Message-ID: <20231205182011.1976568-7-stefanha@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
This commit is contained in:
Stefan Hajnoczi 2023-12-05 13:20:03 -05:00 • committed by Kevin Wolf
parent 6bc30f1949
commit b49f4755c7
41 changed files with 104 additions and 1169 deletions
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234
block.c
View file

@ -1625,7 +1625,6 @@ static int no_coroutine_fn GRAPH_UNLOCKED
bdrv_open_driver(BlockDriverState *bs, BlockDriver *drv, const char *node_name,
QDict *options, int open_flags, Error **errp)
{
AioContext *ctx;
Error *local_err = NULL;
int i, ret;
GLOBAL_STATE_CODE();
@ -1673,21 +1672,15 @@ bdrv_open_driver(BlockDriverState *bs, BlockDriver *drv, const char *node_name,
bs->supported_read_flags |= BDRV_REQ_REGISTERED_BUF;
bs->supported_write_flags |= BDRV_REQ_REGISTERED_BUF;
/* Get the context after .bdrv_open, it can change the context */
ctx = bdrv_get_aio_context(bs);
aio_context_acquire(ctx);
ret = bdrv_refresh_total_sectors(bs, bs->total_sectors);
if (ret < 0) {
error_setg_errno(errp, -ret, "Could not refresh total sector count");
aio_context_release(ctx);
return ret;
}
bdrv_graph_rdlock_main_loop();
bdrv_refresh_limits(bs, NULL, &local_err);
bdrv_graph_rdunlock_main_loop();
aio_context_release(ctx);
if (local_err) {
error_propagate(errp, local_err);
@ -3062,7 +3055,7 @@ bdrv_attach_child_common(BlockDriverState *child_bs,
Transaction *tran, Error **errp)
{
BdrvChild *new_child;
AioContext *parent_ctx, *new_child_ctx;
AioContext *parent_ctx;
AioContext *child_ctx = bdrv_get_aio_context(child_bs);
assert(child_class->get_parent_desc);
@ -3114,12 +3107,6 @@ bdrv_attach_child_common(BlockDriverState *child_bs,
}
}
new_child_ctx = bdrv_get_aio_context(child_bs);
if (new_child_ctx != child_ctx) {
aio_context_release(child_ctx);
aio_context_acquire(new_child_ctx);
}
bdrv_ref(child_bs);
/*
* Let every new BdrvChild start with a drained parent. Inserting the child
@ -3149,11 +3136,6 @@ bdrv_attach_child_common(BlockDriverState *child_bs,
};
tran_add(tran, &bdrv_attach_child_common_drv, s);
if (new_child_ctx != child_ctx) {
aio_context_release(new_child_ctx);
aio_context_acquire(child_ctx);
}
return new_child;
}
@ -3605,7 +3587,6 @@ int bdrv_open_backing_file(BlockDriverState *bs, QDict *parent_options,
int ret = 0;
bool implicit_backing = false;
BlockDriverState *backing_hd;
AioContext *backing_hd_ctx;
QDict *options;
QDict *tmp_parent_options = NULL;
Error *local_err = NULL;
@ -3691,11 +3672,8 @@ int bdrv_open_backing_file(BlockDriverState *bs, QDict *parent_options,
/* Hook up the backing file link; drop our reference, bs owns the
* backing_hd reference now */
backing_hd_ctx = bdrv_get_aio_context(backing_hd);
aio_context_acquire(backing_hd_ctx);
ret = bdrv_set_backing_hd(bs, backing_hd, errp);
bdrv_unref(backing_hd);
aio_context_release(backing_hd_ctx);
if (ret < 0) {
goto free_exit;
@ -3780,7 +3758,6 @@ BdrvChild *bdrv_open_child(const char *filename,
{
BlockDriverState *bs;
BdrvChild *child;
AioContext *ctx;
GLOBAL_STATE_CODE();
@ -3791,11 +3768,8 @@ BdrvChild *bdrv_open_child(const char *filename,
}
bdrv_graph_wrlock();
ctx = bdrv_get_aio_context(bs);
aio_context_acquire(ctx);
child = bdrv_attach_child(parent, bs, bdref_key, child_class, child_role,
errp);
aio_context_release(ctx);
bdrv_graph_wrunlock();
return child;
@ -3881,7 +3855,6 @@ static BlockDriverState *bdrv_append_temp_snapshot(BlockDriverState *bs,
int64_t total_size;
QemuOpts *opts = NULL;
BlockDriverState *bs_snapshot = NULL;
AioContext *ctx = bdrv_get_aio_context(bs);
int ret;
GLOBAL_STATE_CODE();
@ -3890,9 +3863,7 @@ static BlockDriverState *bdrv_append_temp_snapshot(BlockDriverState *bs,
instead of opening 'filename' directly */
/* Get the required size from the image */
aio_context_acquire(ctx);
total_size = bdrv_getlength(bs);
aio_context_release(ctx);
if (total_size < 0) {
error_setg_errno(errp, -total_size, "Could not get image size");
@ -3927,10 +3898,7 @@ static BlockDriverState *bdrv_append_temp_snapshot(BlockDriverState *bs,
goto out;
}
aio_context_acquire(ctx);
ret = bdrv_append(bs_snapshot, bs, errp);
aio_context_release(ctx);
if (ret < 0) {
bs_snapshot = NULL;
goto out;
@ -3974,7 +3942,6 @@ bdrv_open_inherit(const char *filename, const char *reference, QDict *options,
Error *local_err = NULL;
QDict *snapshot_options = NULL;
int snapshot_flags = 0;
AioContext *ctx = qemu_get_aio_context();
assert(!child_class || !flags);
assert(!child_class == !parent);
@ -4115,12 +4082,10 @@ bdrv_open_inherit(const char *filename, const char *reference, QDict *options,
/* Not requesting BLK_PERM_CONSISTENT_READ because we're only
* looking at the header to guess the image format. This works even
* in cases where a guest would not see a consistent state. */
ctx = bdrv_get_aio_context(file_bs);
aio_context_acquire(ctx);
AioContext *ctx = bdrv_get_aio_context(file_bs);
file = blk_new(ctx, 0, BLK_PERM_ALL);
blk_insert_bs(file, file_bs, &local_err);
bdrv_unref(file_bs);
aio_context_release(ctx);
if (local_err) {
goto fail;
@ -4167,13 +4132,8 @@ bdrv_open_inherit(const char *filename, const char *reference, QDict *options,
goto fail;
}
/* The AioContext could have changed during bdrv_open_common() */
ctx = bdrv_get_aio_context(bs);
if (file) {
aio_context_acquire(ctx);
blk_unref(file);
aio_context_release(ctx);
file = NULL;
}
@ -4231,16 +4191,13 @@ bdrv_open_inherit(const char *filename, const char *reference, QDict *options,
* (snapshot_bs); thus, we have to drop the strong reference to bs
* (which we obtained by calling bdrv_new()). bs will not be deleted,
* though, because the overlay still has a reference to it. */
aio_context_acquire(ctx);
bdrv_unref(bs);
aio_context_release(ctx);
bs = snapshot_bs;
}
return bs;
fail:
aio_context_acquire(ctx);
blk_unref(file);
qobject_unref(snapshot_options);
qobject_unref(bs->explicit_options);
@ -4249,14 +4206,11 @@ fail:
bs->options = NULL;
bs->explicit_options = NULL;
bdrv_unref(bs);
aio_context_release(ctx);
error_propagate(errp, local_err);
return NULL;
close_and_fail:
aio_context_acquire(ctx);
bdrv_unref(bs);
aio_context_release(ctx);
qobject_unref(snapshot_options);
qobject_unref(options);
error_propagate(errp, local_err);
@ -4540,12 +4494,7 @@ void bdrv_reopen_queue_free(BlockReopenQueue *bs_queue)
if (bs_queue) {
BlockReopenQueueEntry *bs_entry, *next;
QTAILQ_FOREACH_SAFE(bs_entry, bs_queue, entry, next) {
AioContext *ctx = bdrv_get_aio_context(bs_entry->state.bs);
aio_context_acquire(ctx);
bdrv_drained_end(bs_entry->state.bs);
aio_context_release(ctx);
qobject_unref(bs_entry->state.explicit_options);
qobject_unref(bs_entry->state.options);
g_free(bs_entry);
@ -4577,7 +4526,6 @@ int bdrv_reopen_multiple(BlockReopenQueue *bs_queue, Error **errp)
{
int ret = -1;
BlockReopenQueueEntry *bs_entry, *next;
AioContext *ctx;
Transaction *tran = tran_new();
g_autoptr(GSList) refresh_list = NULL;
@ -4586,10 +4534,7 @@ int bdrv_reopen_multiple(BlockReopenQueue *bs_queue, Error **errp)
GLOBAL_STATE_CODE();
QTAILQ_FOREACH(bs_entry, bs_queue, entry) {
ctx = bdrv_get_aio_context(bs_entry->state.bs);
aio_context_acquire(ctx);
ret = bdrv_flush(bs_entry->state.bs);
aio_context_release(ctx);
if (ret < 0) {
error_setg_errno(errp, -ret, "Error flushing drive");
goto abort;
@ -4598,10 +4543,7 @@ int bdrv_reopen_multiple(BlockReopenQueue *bs_queue, Error **errp)
QTAILQ_FOREACH(bs_entry, bs_queue, entry) {
assert(bs_entry->state.bs->quiesce_counter > 0);
ctx = bdrv_get_aio_context(bs_entry->state.bs);
aio_context_acquire(ctx);
ret = bdrv_reopen_prepare(&bs_entry->state, bs_queue, tran, errp);
aio_context_release(ctx);
if (ret < 0) {
goto abort;
}
@ -4644,10 +4586,7 @@ int bdrv_reopen_multiple(BlockReopenQueue *bs_queue, Error **errp)
* to first element.
*/
QTAILQ_FOREACH_REVERSE(bs_entry, bs_queue, entry) {
ctx = bdrv_get_aio_context(bs_entry->state.bs);
aio_context_acquire(ctx);
bdrv_reopen_commit(&bs_entry->state);
aio_context_release(ctx);
}
bdrv_graph_wrlock();
@ -4658,10 +4597,7 @@ int bdrv_reopen_multiple(BlockReopenQueue *bs_queue, Error **errp)
BlockDriverState *bs = bs_entry->state.bs;
if (bs->drv->bdrv_reopen_commit_post) {
ctx = bdrv_get_aio_context(bs);
aio_context_acquire(ctx);
bs->drv->bdrv_reopen_commit_post(&bs_entry->state);
aio_context_release(ctx);
}
}
@ -4675,10 +4611,7 @@ abort:
QTAILQ_FOREACH_SAFE(bs_entry, bs_queue, entry, next) {
if (bs_entry->prepared) {
ctx = bdrv_get_aio_context(bs_entry->state.bs);
aio_context_acquire(ctx);
bdrv_reopen_abort(&bs_entry->state);
aio_context_release(ctx);
}
}
@ -4691,24 +4624,13 @@ cleanup:
int bdrv_reopen(BlockDriverState *bs, QDict *opts, bool keep_old_opts,
Error **errp)
{
AioContext *ctx = bdrv_get_aio_context(bs);
BlockReopenQueue *queue;
int ret;
GLOBAL_STATE_CODE();
queue = bdrv_reopen_queue(NULL, bs, opts, keep_old_opts);
if (ctx != qemu_get_aio_context()) {
aio_context_release(ctx);
}
ret = bdrv_reopen_multiple(queue, errp);
if (ctx != qemu_get_aio_context()) {
aio_context_acquire(ctx);
}
return ret;
return bdrv_reopen_multiple(queue, errp);
}
int bdrv_reopen_set_read_only(BlockDriverState *bs, bool read_only,
@ -4760,7 +4682,6 @@ bdrv_reopen_parse_file_or_backing(BDRVReopenState *reopen_state,
const char *child_name = is_backing ? "backing" : "file";
QObject *value;
const char *str;
AioContext *ctx, *old_ctx;
bool has_child;
int ret;
@ -4844,13 +4765,6 @@ bdrv_reopen_parse_file_or_backing(BDRVReopenState *reopen_state,
bdrv_drained_begin(old_child_bs);
}
old_ctx = bdrv_get_aio_context(bs);
ctx = bdrv_get_aio_context(new_child_bs);
if (old_ctx != ctx) {
aio_context_release(old_ctx);
aio_context_acquire(ctx);
}
bdrv_graph_rdunlock_main_loop();
bdrv_graph_wrlock();
@ -4859,11 +4773,6 @@ bdrv_reopen_parse_file_or_backing(BDRVReopenState *reopen_state,
bdrv_graph_wrunlock();
if (old_ctx != ctx) {
aio_context_release(ctx);
aio_context_acquire(old_ctx);
}
if (old_child_bs) {
bdrv_drained_end(old_child_bs);
bdrv_unref(old_child_bs);
@ -5537,7 +5446,6 @@ int bdrv_append(BlockDriverState *bs_new, BlockDriverState *bs_top,
int ret;
BdrvChild *child;
Transaction *tran = tran_new();
AioContext *old_context, *new_context = NULL;
GLOBAL_STATE_CODE();
@ -5545,21 +5453,8 @@ int bdrv_append(BlockDriverState *bs_new, BlockDriverState *bs_top,
assert(!bs_new->backing);
bdrv_graph_rdunlock_main_loop();
old_context = bdrv_get_aio_context(bs_top);
bdrv_drained_begin(bs_top);
/*
* bdrv_drained_begin() requires that only the AioContext of the drained
* node is locked, and at this point it can still differ from the AioContext
* of bs_top.
*/
new_context = bdrv_get_aio_context(bs_new);
aio_context_release(old_context);
aio_context_acquire(new_context);
bdrv_drained_begin(bs_new);
aio_context_release(new_context);
aio_context_acquire(old_context);
new_context = NULL;
bdrv_graph_wrlock();
@ -5571,18 +5466,6 @@ int bdrv_append(BlockDriverState *bs_new, BlockDriverState *bs_top,
goto out;
}
/*
* bdrv_attach_child_noperm could change the AioContext of bs_top and
* bs_new, but at least they are in the same AioContext now. This is the
* AioContext that we need to lock for the rest of the function.
*/
new_context = bdrv_get_aio_context(bs_top);
if (old_context != new_context) {
aio_context_release(old_context);
aio_context_acquire(new_context);
}
ret = bdrv_replace_node_noperm(bs_top, bs_new, true, tran, errp);
if (ret < 0) {
goto out;
@ -5598,11 +5481,6 @@ out:
bdrv_drained_end(bs_top);
bdrv_drained_end(bs_new);
if (new_context && old_context != new_context) {
aio_context_release(new_context);
aio_context_acquire(old_context);
}
return ret;
}
@ -5697,12 +5575,8 @@ BlockDriverState *bdrv_insert_node(BlockDriverState *bs, QDict *options,
GLOBAL_STATE_CODE();
aio_context_release(ctx);
aio_context_acquire(qemu_get_aio_context());
new_node_bs = bdrv_new_open_driver_opts(drv, node_name, options, flags,
errp);
aio_context_release(qemu_get_aio_context());
aio_context_acquire(ctx);
assert(bdrv_get_aio_context(bs) == ctx);
options = NULL; /* bdrv_new_open_driver() eats options */
@ -7037,12 +6911,9 @@ void bdrv_activate_all(Error **errp)
GRAPH_RDLOCK_GUARD_MAINLOOP();
for (bs = bdrv_first(&it); bs; bs = bdrv_next(&it)) {
AioContext *aio_context = bdrv_get_aio_context(bs);
int ret;
aio_context_acquire(aio_context);
ret = bdrv_activate(bs, errp);
aio_context_release(aio_context);
if (ret < 0) {
bdrv_next_cleanup(&it);
return;
@ -7137,20 +7008,10 @@ int bdrv_inactivate_all(void)
BlockDriverState *bs = NULL;
BdrvNextIterator it;
int ret = 0;
GSList *aio_ctxs = NULL, *ctx;
GLOBAL_STATE_CODE();
GRAPH_RDLOCK_GUARD_MAINLOOP();
for (bs = bdrv_first(&it); bs; bs = bdrv_next(&it)) {
AioContext *aio_context = bdrv_get_aio_context(bs);
if (!g_slist_find(aio_ctxs, aio_context)) {
aio_ctxs = g_slist_prepend(aio_ctxs, aio_context);
aio_context_acquire(aio_context);
}
}
for (bs = bdrv_first(&it); bs; bs = bdrv_next(&it)) {
/* Nodes with BDS parents are covered by recursion from the last
* parent that gets inactivated. Don't inactivate them a second
@ -7161,17 +7022,10 @@ int bdrv_inactivate_all(void)
ret = bdrv_inactivate_recurse(bs);
if (ret < 0) {
bdrv_next_cleanup(&it);
goto out;
break;
}
}
out:
for (ctx = aio_ctxs; ctx != NULL; ctx = ctx->next) {
AioContext *aio_context = ctx->data;
aio_context_release(aio_context);
}
g_slist_free(aio_ctxs);
return ret;
}
@ -7257,11 +7111,8 @@ void bdrv_unref(BlockDriverState *bs)
static void bdrv_schedule_unref_bh(void *opaque)
{
BlockDriverState *bs = opaque;
AioContext *ctx = bdrv_get_aio_context(bs);
aio_context_acquire(ctx);
bdrv_unref(bs);
aio_context_release(ctx);
}
/*
@ -7398,8 +7249,6 @@ void bdrv_img_create(const char *filename, const char *fmt,
return;
}
aio_context_acquire(qemu_get_aio_context());
/* Create parameter list */
create_opts = qemu_opts_append(create_opts, drv->create_opts);
create_opts = qemu_opts_append(create_opts, proto_drv->create_opts);
@ -7549,7 +7398,6 @@ out:
qemu_opts_del(opts);
qemu_opts_free(create_opts);
error_propagate(errp, local_err);
aio_context_release(qemu_get_aio_context());
}
AioContext *bdrv_get_aio_context(BlockDriverState *bs)
@ -7585,29 +7433,12 @@ void coroutine_fn bdrv_co_leave(BlockDriverState *bs, AioContext *old_ctx)
void coroutine_fn bdrv_co_lock(BlockDriverState *bs)
{
AioContext *ctx = bdrv_get_aio_context(bs);
/* In the main thread, bs->aio_context won't change concurrently */
assert(qemu_get_current_aio_context() == qemu_get_aio_context());
/*
* We're in coroutine context, so we already hold the lock of the main
* loop AioContext. Don't lock it twice to avoid deadlocks.
*/
assert(qemu_in_coroutine());
if (ctx != qemu_get_aio_context()) {
aio_context_acquire(ctx);
}
/* TODO removed in next patch */
}
void coroutine_fn bdrv_co_unlock(BlockDriverState *bs)
{
AioContext *ctx = bdrv_get_aio_context(bs);
assert(qemu_in_coroutine());
if (ctx != qemu_get_aio_context()) {
aio_context_release(ctx);
}
/* TODO removed in next patch */
}
static void bdrv_do_remove_aio_context_notifier(BdrvAioNotifier *ban)
@ -7728,21 +7559,8 @@ static void bdrv_set_aio_context_commit(void *opaque)
BdrvStateSetAioContext *state = (BdrvStateSetAioContext *) opaque;
BlockDriverState *bs = (BlockDriverState *) state->bs;
AioContext *new_context = state->new_ctx;
AioContext *old_context = bdrv_get_aio_context(bs);
/*
* Take the old AioContex when detaching it from bs.
* At this point, new_context lock is already acquired, and we are now
* also taking old_context. This is safe as long as bdrv_detach_aio_context
* does not call AIO_POLL_WHILE().
*/
if (old_context != qemu_get_aio_context()) {
aio_context_acquire(old_context);
}
bdrv_detach_aio_context(bs);
if (old_context != qemu_get_aio_context()) {
aio_context_release(old_context);
}
bdrv_attach_aio_context(bs, new_context);
}
@ -7827,7 +7645,6 @@ int bdrv_try_change_aio_context(BlockDriverState *bs, AioContext *ctx,
Transaction *tran;
GHashTable *visited;
int ret;
AioContext *old_context = bdrv_get_aio_context(bs);
GLOBAL_STATE_CODE();
/*
@ -7857,34 +7674,7 @@ int bdrv_try_change_aio_context(BlockDriverState *bs, AioContext *ctx,
return -EPERM;
}
/*
* Release old AioContext, it won't be needed anymore, as all
* bdrv_drained_begin() have been called already.
*/
if (qemu_get_aio_context() != old_context) {
aio_context_release(old_context);
}
/*
* Acquire new AioContext since bdrv_drained_end() is going to be called
* after we switched all nodes in the new AioContext, and the function
* assumes that the lock of the bs is always taken.
*/
if (qemu_get_aio_context() != ctx) {
aio_context_acquire(ctx);
}
tran_commit(tran);
if (qemu_get_aio_context() != ctx) {
aio_context_release(ctx);
}
/* Re-acquire the old AioContext, since the caller takes and releases it. */
if (qemu_get_aio_context() != old_context) {
aio_context_acquire(old_context);
}
return 0;
}
@ -8006,7 +7796,6 @@ BlockDriverState *check_to_replace_node(BlockDriverState *parent_bs,
const char *node_name, Error **errp)
{
BlockDriverState *to_replace_bs = bdrv_find_node(node_name);
AioContext *aio_context;
GLOBAL_STATE_CODE();
@ -8015,12 +7804,8 @@ BlockDriverState *check_to_replace_node(BlockDriverState *parent_bs,
return NULL;
}
aio_context = bdrv_get_aio_context(to_replace_bs);
aio_context_acquire(aio_context);
if (bdrv_op_is_blocked(to_replace_bs, BLOCK_OP_TYPE_REPLACE, errp)) {
to_replace_bs = NULL;
goto out;
return NULL;
}
/* We don't want arbitrary node of the BDS chain to be replaced only the top
@ -8033,12 +7818,9 @@ BlockDriverState *check_to_replace_node(BlockDriverState *parent_bs,
"because it cannot be guaranteed that doing so would not "
"lead to an abrupt change of visible data",
node_name, parent_bs->node_name);
to_replace_bs = NULL;
goto out;
return NULL;
}
out:
aio_context_release(aio_context);
return to_replace_bs;
}