Re: [PATCH] libxfs: check all defer ops types

[Eric Sandeen <sandeen@xxxxxxxxxxx>]

On 10/26/18 2:02 PM, Eric Sandeen wrote:
> On 10/26/18 11:19 AM, Darrick J. Wong wrote:
>> From: Darrick J. Wong <darrick.wong@xxxxxxxxxx>
>>
>> Make sure we have all the defer ops types loaded before proceeding.
> 
> So, the only reason we have this problem is that userspace doesn't
> exactly share the code which handles all the defer ops.
> 
> I think this really needs to be a BUILD_BUG_ON if anything, by the
> time we get to runtime it's really too late, and a weird thing to
> run at every invocation.
> 
> The only thing I can think of is to make an array containing each
> of the xfs_defer_op_types, and iterate over it in some sort of
> xfs_defer_ops_init(), then we can compare the size of that array to
> XFS_DEFER_OPS_TYPE_MAX with a BUILD_BUG_ON.  Worth it?

Uh, or just make a statically initialized array?
I guess nothing about this directly enforces that the ->type number
is in the right slot of the array.

static const struct
xfs_defer_op_type *defer_op_types[XFS_DEFER_OPS_TYPE_MAX] = {
       xfs_bmap_update_defer_type,
       xfs_refcount_update_defer_type,
       xfs_rmap_update_defer_type,
       xfs_extent_free_defer_type,
       xfs_agfl_free_defer_type,
};