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block: add bdrv_attach_child_common() transaction action
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Split out no-perm part of bdrv_root_attach_child() into separate
transaction action. bdrv_root_attach_child() now moves to new
permission update paradigm: first update graph relations then update
permissions.

qsd-jobs test output updated. Seems now permission update goes in
another order. Still, the test comment say that we only want to check
that command doesn't crash, and it's still so.

Error message is a bit misleading as it looks like job was added first.
But actually in new paradigm of graph update we can't distinguish such
things. We should update the error message, but let's not do it now.

Signed-off-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
Message-Id: <20210428151804.439460-19-vsementsov@virtuozzo.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
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@kevmw
Vladimir Sementsov-Ogievskiy authored and kevmw committed Apr 30, 2021
1 parent 3bb0e29 commit 548a74c
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Showing 2 changed files with 137 additions and 55 deletions.
190 changes: 136 additions & 54 deletions block.c
View file
Expand Up @@ -2955,37 +2955,74 @@ static void bdrv_replace_child(BdrvChild *child, BlockDriverState *new_bs)
}
}

/*
* This function steals the reference to child_bs from the caller.
* That reference is later dropped by bdrv_root_unref_child().
*
* On failure NULL is returned, errp is set and the reference to
* child_bs is also dropped.
*
* The caller must hold the AioContext lock @child_bs, but not that of @ctx
* (unless @child_bs is already in @ctx).
*/
BdrvChild *bdrv_root_attach_child(BlockDriverState *child_bs,
const char *child_name,
const BdrvChildClass *child_class,
BdrvChildRole child_role,
uint64_t perm, uint64_t shared_perm,
void *opaque, Error **errp)
static void bdrv_remove_empty_child(BdrvChild *child)
{
BdrvChild *child;
Error *local_err = NULL;
int ret;
AioContext *ctx;
assert(!child->bs);
QLIST_SAFE_REMOVE(child, next);
g_free(child->name);
g_free(child);
}

ret = bdrv_check_update_perm(child_bs, NULL, perm, shared_perm, NULL, errp);
if (ret < 0) {
bdrv_abort_perm_update(child_bs);
bdrv_unref(child_bs);
return NULL;
typedef struct BdrvAttachChildCommonState {
BdrvChild **child;
AioContext *old_parent_ctx;
AioContext *old_child_ctx;
} BdrvAttachChildCommonState;

static void bdrv_attach_child_common_abort(void *opaque)
{
BdrvAttachChildCommonState *s = opaque;
BdrvChild *child = *s->child;
BlockDriverState *bs = child->bs;

bdrv_replace_child_noperm(child, NULL);

if (bdrv_get_aio_context(bs) != s->old_child_ctx) {
bdrv_try_set_aio_context(bs, s->old_child_ctx, &error_abort);
}

child = g_new(BdrvChild, 1);
*child = (BdrvChild) {
if (bdrv_child_get_parent_aio_context(child) != s->old_parent_ctx) {
GSList *ignore = g_slist_prepend(NULL, child);

child->klass->can_set_aio_ctx(child, s->old_parent_ctx, &ignore,
&error_abort);
g_slist_free(ignore);
ignore = g_slist_prepend(NULL, child);
child->klass->set_aio_ctx(child, s->old_parent_ctx, &ignore);

g_slist_free(ignore);
}

bdrv_unref(bs);
bdrv_remove_empty_child(child);
*s->child = NULL;
}

static TransactionActionDrv bdrv_attach_child_common_drv = {
.abort = bdrv_attach_child_common_abort,
.clean = g_free,
};

/*
* Common part of attaching bdrv child to bs or to blk or to job
*/
static int bdrv_attach_child_common(BlockDriverState *child_bs,
const char *child_name,
const BdrvChildClass *child_class,
BdrvChildRole child_role,
uint64_t perm, uint64_t shared_perm,
void *opaque, BdrvChild **child,
Transaction *tran, Error **errp)
{
BdrvChild *new_child;
AioContext *parent_ctx;
AioContext *child_ctx = bdrv_get_aio_context(child_bs);

assert(child);
assert(*child == NULL);

new_child = g_new(BdrvChild, 1);
*new_child = (BdrvChild) {
.bs = NULL,
.name = g_strdup(child_name),
.klass = child_class,
Expand All @@ -2995,37 +3032,92 @@ BdrvChild *bdrv_root_attach_child(BlockDriverState *child_bs,
.opaque = opaque,
};

ctx = bdrv_child_get_parent_aio_context(child);

/* If the AioContexts don't match, first try to move the subtree of
/*
* If the AioContexts don't match, first try to move the subtree of
* child_bs into the AioContext of the new parent. If this doesn't work,
* try moving the parent into the AioContext of child_bs instead. */
if (bdrv_get_aio_context(child_bs) != ctx) {
ret = bdrv_try_set_aio_context(child_bs, ctx, &local_err);
* try moving the parent into the AioContext of child_bs instead.
*/
parent_ctx = bdrv_child_get_parent_aio_context(new_child);
if (child_ctx != parent_ctx) {
Error *local_err = NULL;
int ret = bdrv_try_set_aio_context(child_bs, parent_ctx, &local_err);

if (ret < 0 && child_class->can_set_aio_ctx) {
GSList *ignore = g_slist_prepend(NULL, child);
ctx = bdrv_get_aio_context(child_bs);
if (child_class->can_set_aio_ctx(child, ctx, &ignore, NULL)) {
GSList *ignore = g_slist_prepend(NULL, new_child);
if (child_class->can_set_aio_ctx(new_child, child_ctx, &ignore,
NULL))
{
error_free(local_err);
ret = 0;
g_slist_free(ignore);
ignore = g_slist_prepend(NULL, child);
child_class->set_aio_ctx(child, ctx, &ignore);
ignore = g_slist_prepend(NULL, new_child);
child_class->set_aio_ctx(new_child, child_ctx, &ignore);
}
g_slist_free(ignore);
}

if (ret < 0) {
error_propagate(errp, local_err);
g_free(child);
bdrv_abort_perm_update(child_bs);
bdrv_unref(child_bs);
return NULL;
bdrv_remove_empty_child(new_child);
return ret;
}
}

/* This performs the matching bdrv_set_perm() for the above check. */
bdrv_replace_child(child, child_bs);
bdrv_ref(child_bs);
bdrv_replace_child_noperm(new_child, child_bs);

*child = new_child;

BdrvAttachChildCommonState *s = g_new(BdrvAttachChildCommonState, 1);
*s = (BdrvAttachChildCommonState) {
.child = child,
.old_parent_ctx = parent_ctx,
.old_child_ctx = child_ctx,
};
tran_add(tran, &bdrv_attach_child_common_drv, s);

return 0;
}

static void bdrv_detach_child(BdrvChild *child)
{
bdrv_replace_child(child, NULL);
bdrv_remove_empty_child(child);
}

/*
* This function steals the reference to child_bs from the caller.
* That reference is later dropped by bdrv_root_unref_child().
*
* On failure NULL is returned, errp is set and the reference to
* child_bs is also dropped.
*
* The caller must hold the AioContext lock @child_bs, but not that of @ctx
* (unless @child_bs is already in @ctx).
*/
BdrvChild *bdrv_root_attach_child(BlockDriverState *child_bs,
const char *child_name,
const BdrvChildClass *child_class,
BdrvChildRole child_role,
uint64_t perm, uint64_t shared_perm,
void *opaque, Error **errp)
{
int ret;
BdrvChild *child = NULL;
Transaction *tran = tran_new();

ret = bdrv_attach_child_common(child_bs, child_name, child_class,
child_role, perm, shared_perm, opaque,
&child, tran, errp);
if (ret < 0) {
bdrv_unref(child_bs);
return NULL;
}

ret = bdrv_refresh_perms(child_bs, errp);
tran_finalize(tran, ret);

bdrv_unref(child_bs);
return child;
}

Expand Down Expand Up @@ -3067,16 +3159,6 @@ BdrvChild *bdrv_attach_child(BlockDriverState *parent_bs,
return child;
}

static void bdrv_detach_child(BdrvChild *child)
{
QLIST_SAFE_REMOVE(child, next);

bdrv_replace_child(child, NULL);

g_free(child->name);
g_free(child);
}

/* Callers must ensure that child->frozen is false. */
void bdrv_root_unref_child(BdrvChild *child)
{
Expand Down
2 changes: 1 addition & 1 deletion tests/qemu-iotests/tests/qsd-jobs.out
View file
Expand Up @@ -16,7 +16,7 @@ QMP_VERSION
{"return": {}}
{"timestamp": {"seconds": TIMESTAMP, "microseconds": TIMESTAMP}, "event": "JOB_STATUS_CHANGE", "data": {"status": "created", "id": "job0"}}
{"timestamp": {"seconds": TIMESTAMP, "microseconds": TIMESTAMP}, "event": "JOB_STATUS_CHANGE", "data": {"status": "null", "id": "job0"}}
{"error": {"class": "GenericError", "desc": "Conflicts with use by a block device as 'root', which uses 'write' on fmt_base"}}
{"error": {"class": "GenericError", "desc": "Conflicts with use by stream job 'job0' as 'intermediate node', which does not allow 'write' on fmt_base"}}
{"return": {}}
{"timestamp": {"seconds": TIMESTAMP, "microseconds": TIMESTAMP}, "event": "BLOCK_EXPORT_DELETED", "data": {"id": "export1"}}
*** done

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