On 5/22/17 2:07 PM, Christoph Hellwig wrote:
> On Mon, May 22, 2017 at 10:48:14AM -0500, Eric Sandeen wrote:
>> This was throwing unaligned access warnings on sparc64:
>>
>> Kernel unaligned access at TPC[1043c088] xfs_btree_visit_blocks+0x88/0xe0 [xfs]
>>
>> Signed-off-by: Eric Sandeen <sandeen@xxxxxxxxxx>
>> ---
>>
>> diff --git a/fs/xfs/libxfs/xfs_btree.c b/fs/xfs/libxfs/xfs_btree.c
>> index 5392674..84089f8 100644
>> --- a/fs/xfs/libxfs/xfs_btree.c
>> +++ b/fs/xfs/libxfs/xfs_btree.c
>> @@ -4395,7 +4395,7 @@ struct xfs_btree_split_args {
>> xfs_btree_readahead_ptr(cur, ptr, 1);
>>
>> /* save for the next iteration of the loop */
>> - lptr = *ptr;
>> + lptr = get_unaligned(ptr);
>
> Hm.. We don't really do this for the return value of of xfs_btree_ptr_addr
> anywhere else. So if it really returns something not suitably enough
> aligned we're in much deeper trouble.
Yeah, I took a quick look, probably too quick. But I think the problem
here is that it's a structure copy, which is unusual compared to most of
the other callers:
union xfs_btree_ptr lptr;
lptr = *ptr;
and is probably what's generating the warning, right? I guess a better
comment and/or commit log would be in order.
I haven't looked at every other caller but several end up calling
xfs_btree_copy_ptrs which does a memcpy.
Hm, ok, maybe we should just be using that helper...
xfs_btree_copy_ptrs(cur, &lptr, ptr, 1);
?
-Eric
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