Re: [Qemu-block] [PATCH v2 04/17] qmp: Add block-dirty-bitmap-add and block-dirty-bitmap-remove

[Stefan Hajnoczi]

On Mon, Mar 02, 2015 at 06:19:50PM -0500, John Snow wrote:
> +static BdrvDirtyBitmap *block_dirty_bitmap_lookup(const char *node,
> +                                                  const char *name,
> +                                                  BlockDriverState **pbs,
> +                                                  Error **errp)
> +{
> +    BlockDriverState *bs;
> +    BdrvDirtyBitmap *bitmap;
> +
> +    if (!node) {
> +        error_setg(errp, "Node cannot be NULL");
> +        return NULL;
> +    }
> +    if (!name) {
> +        error_setg(errp, "Bitmap name cannot be NULL");
> +        return NULL;
> +    }
> +
> +    bs = bdrv_lookup_bs(node, node, NULL);
> +    if (!bs) {
> +        error_setg(errp, "Node '%s' not found", node);
> +        return NULL;
> +    }
> +
> +    /* If caller provided a BDS*, provide the result of that lookup, too. */
> +    if (pbs) {
> +        *pbs = bs;
> +    }
> +
> +    bitmap = bdrv_find_dirty_bitmap(bs, name);

AioContext is not held here.  I'm worried that a block job (running
under the AioContext) could change or delete the bitmap at the same time
as this function is running.

This function should acquire the AioContext before calling
bdrv_find_dirty_bitmap() and fill out an AioContext** parameter so the
caller can continue to use bs/bitmap under the lock.

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