Re: [Xen-devel] struct blkif_request_segment_aligned

["Jan Beulich" <JBeulich@xxxxxxxx>]

>>> On 03.02.14 at 10:40, Ian Campbell <Ian.Campbell@xxxxxxxxxx> wrote:
> On Fri, 2014-01-31 at 12:04 +0000, Jan Beulich wrote:
>> Roger,
>> 
>> so you introduced this, yet looking in a little closer detail I can't seem
>> to understand why: struct blkif_request_segment is identical in layout,
>> the sole difference between the two is that in the new structure the
>> padding field has a name, whereas in the old one it doesn't.
> 
> Is this something to do with Linux' use of __attribute__((packed)) once
> again causing confusion? (I really hope not API deviation...)

Yes, I think it has to do with Linux'es way of defining these
structures: My assumption is that the embedded (but not such
attributed) definition of struct blkif_request_segment inside struct
struct blkif_request_rw was assumed to also be packed (which it
isn't, or else upstream Linux front-/backends wouldn't work with
other back-/frontends), thus apparently making it necessary to
have an "aligned" (i.e. un-packed) variant thereof.

Jan

>> I'd really like to get rid of this redundant type again, unless there's a
>> reason for it to be there which I'm overlooking.
>> 
>> Jan
>> 
>> 
>> _______________________________________________
>> Xen-devel mailing list
>> Xen-devel@xxxxxxxxxxxxx 
>> http://lists.xen.org/xen-devel 




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