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copy-before-write: Fix open with child in iothread 

The AioContext lock must not be held for bdrv_open_child(), but it is
necessary for the following operations, in particular those using nested
event loops in coroutine wrappers.

Temporarily dropping the main AioContext lock is not necessary because
we know we run in the main thread.

Signed-off-by: Kevin Wolf <kwolf@redhat.com>
Message-Id: <20230525124713.401149-9-kwolf@redhat.com>
Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
This commit is contained in:
Kevin Wolf 2023-05-25 14:47:09 +02:00
parent 6e01215932
commit 9102f2ebdb
1 changed files with 16 additions and 5 deletions
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21
block/copy-before-write.c
View File

@ -412,6 +412,7 @@ static int cbw_open(BlockDriverState *bs, QDict *options, int flags,
int64_t cluster_size;
g_autoptr(BlockdevOptions) full_opts = NULL;
BlockdevOptionsCbw *opts;
AioContext *ctx;
int ret;
full_opts = cbw_parse_options(options, errp);
@ -432,11 +433,15 @@ static int cbw_open(BlockDriverState *bs, QDict *options, int flags,
return -EINVAL;
}
ctx = bdrv_get_aio_context(bs);
aio_context_acquire(ctx);
if (opts->bitmap) {
bitmap = block_dirty_bitmap_lookup(opts->bitmap->node,
opts->bitmap->name, NULL, errp);
if (!bitmap) {
return -EINVAL;
ret = -EINVAL;
goto out;
}
}
s->on_cbw_error = opts->has_on_cbw_error ? opts->on_cbw_error :
@ -454,21 +459,24 @@ static int cbw_open(BlockDriverState *bs, QDict *options, int flags,
s->bcs = block_copy_state_new(bs->file, s->target, bitmap, errp);
if (!s->bcs) {
error_prepend(errp, "Cannot create block-copy-state: ");
return -EINVAL;
ret = -EINVAL;
goto out;
}
cluster_size = block_copy_cluster_size(s->bcs);
s->done_bitmap = bdrv_create_dirty_bitmap(bs, cluster_size, NULL, errp);
if (!s->done_bitmap) {
return -EINVAL;
ret = -EINVAL;
goto out;
}
bdrv_disable_dirty_bitmap(s->done_bitmap);
/* s->access_bitmap starts equal to bcs bitmap */
s->access_bitmap = bdrv_create_dirty_bitmap(bs, cluster_size, NULL, errp);
if (!s->access_bitmap) {
return -EINVAL;
ret = -EINVAL;
goto out;
}
bdrv_disable_dirty_bitmap(s->access_bitmap);
bdrv_dirty_bitmap_merge_internal(s->access_bitmap,
@ -478,7 +486,10 @@ static int cbw_open(BlockDriverState *bs, QDict *options, int flags,
qemu_co_mutex_init(&s->lock);
QLIST_INIT(&s->frozen_read_reqs);
return 0;
ret = 0;
out:
aio_context_release(ctx);
return ret;
}
static void cbw_close(BlockDriverState *bs)