On 05/01/2015 02:39 PM, Mike Christie wrote:
> On 04/30/2015 07:22 AM, Alex Elder wrote:
>>> +/**
>>> + * ceph_start_decoding_compat - decode block with legacy support for
>>> older schemes
>>> + * @p: buffer to decode
>>> + * @end: end of decode buffer
>>> + * @curr_ver: current version of the encoding that the code
>>> supports/encode
>>> + * @compat_ver: oldest version that includes a __u8 compat version field
>>> + * @len_ver: oldest version that includes a __u32 length wrapper
>>> + * @len: buffer to return len of data in buffer
>>> + */
>>> +static inline int ceph_start_decoding_compat(void **p, void *end, u8
>>> curr_ver,
>>> + u8 compat_ver, u8 len_ver, u32 *len)
>>> +{
>>> + u8 struct_ver, struct_compat;
>>> +
>>> + ceph_decode_8_safe(p, end, struct_ver, fail);
>>> + if (struct_ver >= curr_ver) {
>>
>> It seems to me it doesn't matter whether the current code
>> supports the struct compat version or not. What matters
>> is whether the encoded header contains the compat field
>> or not. I'm not sure what determines that.
>
> I am not sure if I understood this comment.
>
> I thought different structs got the compat field in different versions.
> So, I was concerned about a case where we might get a old struct sent to
> us. If the compat field was added to some struct_abc in version 2 and
> that is what we support in the kernel, but some old osd sent us a struct
> that was version 1, then we do not want to do the compat check below.
>
Doh! I wrote the above mail, then realized what you meant.
I think I should have checked the compat_ver passed into the version above.
if (struct_ver >= compat_ver) {
ceph_decode_8_safe(p, end, struct_compat, fail);
if (curr_ver < struct_compat)
>
>>
>>> + ceph_decode_8_safe(p, end, struct_compat, fail);
>>> + if (curr_ver < struct_compat)
>>> + return -EINVAL;
>>> + }
>>> +
>>> + if (struct_ver >= len_ver) {
>>> + ceph_decode_32_safe(p, end, *len, fail);
>>> + } else {
>>> + *len = 0;
>>> + }
>>> +
>>> + return 0;
>>> +fail:
>>> + return -ERANGE;
>>> +}
>>> +
>>> +
>>> #define ceph_encode_need(p, end, n, bad) \
>>> do { \
>>> if (!likely(ceph_has_room(p, end, n))) \
>>>
>>
>
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