2011/4/15 Jeff Layton <[email protected]>:
> On Fri, 15 Apr 2011 08:38:59 -0500
> Steve French <[email protected]> wrote:
>
>> On Fri, Apr 15, 2011 at 5:45 AM, Pavel Shilovsky <[email protected]> wrote:
>> > 2011/4/8 Steve French <[email protected]>:
>> >> Update on cifs vs. smb2 mids, and the smb2 sendrcv2. Jeff had
>> >> suggested more closely matching the cifs and smb2 mids, in particular
>> >> extending the 16 bit cifs mid (multiplex identifier for inflight
>> >> network requests) to the 64 bit size needed for smb2 (and thus masking
>> >> the mid when used for cifs) and having cifs ignore the various smb2
>> >> unique fields in the mid (which makes the mid larger for cifs).
>> >> Since the smb2 code in cifs-2.6.git (put in February and early March)
>> >> has now been rereviewed, the next step in the smb2 merge is posting
>> >> and reviewing the transport routine for smb2 (smb2_sendrcv2 or reusing
>> >> cifs_sendrcv2) - the latter may make more sense if we go to a common
>> >> mid for cifs and smb2. At the fs summit, Jeff and Jeremy and I
>> >> talked about this, but Pavel and others may have opinions on this
>> >> topic. As soon as the cifs merge activity settles down for 2.6.39, I
>> >> plan to post sendrcv2 alternatives and then begin work with Pavel on
>> >> the superblock, file and inode routines and seeing whether for smb2
>> >> they should be smb2 unique (as we originally expected since smb2 is
>> >> handle based, and simpler) and look more like they did in the smb2.ko
>> >> work that Pavel did last summer or should be more common with the cifs
>> >> routines.
>> >>
>> >> --
>> >> Thanks,
>> >>
>> >> Steve
>> >> --
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>> >>
>> >
>> > I suggest to make cifs and smb2 protocol mid structures use common
>> > structure that has equals fields for both and then expand this
>> > structure for protocol-dependent things.
>> >
>> > It can look like this:
>> >
>> > /* one of these for every pending CIFS request to the server */
>> > struct mid_q_entry {
>> > __u8 protocol_id;
>> > struct list_head qhead; /* mids waiting on reply from this server */
>> > int midState; /* wish this were enum but can not pass to
>> > wait_event */
>> > unsigned long when_alloc; /* when mid was created */
>> > #ifdef CONFIG_CIFS_STATS2
>> > unsigned long when_sent; /* time when smb send finished */
>> > unsigned long when_received; /* when demux complete (taken off
>> > wire) */
>> > #endif
>> > bool largeBuf:1; /* if valid response, is pointer to large
>> > buf */
>> > void *resp_buf; /* response buffer */
>> > mid_callback_t *callback; /* call completion callback */
>> > void *callback_data; /* general purpose pointer for callback */
>> > };
>> >
>> > struct cifs_mid_q_entry {
>> > struct mid_q_entry mid_q;
>> > __u16 mid; /* multiplex id */
>> > __u32 sequence_number; /* for CIFS signing */
>> > __u8 command; /* smb command code */
>> > __u16 pid; /* process id */
>> > bool multiRsp:1; /* multiple trans2 responses for one
>> > request */
>> > bool multiEnd:1; /* both received */
>> > };
>> >
>> > struct smb2_mid_q_entry {
>> > struct mid_q_entry mid_q;
>> > __u64 mid; /* multiplex id(s), bigger for smb2 */
>> > __le16 command; /* smb2 command code */
>> > __u32 pid; /* process id - bigger for smb2 than cifs */
>> > };
>>
>> I think nested mid structures (around a base of common mid fields)
>> like the above is going to be the easiest way to handle the differences.
>>
>> I don't understand your PROTOCOL_ID #define though - we
>> identify smb2 vs. cifs via a bool in the tcp server info struct,
>> and presumably if we don't have access to the tcp server
>> info struct we would have to add a field in the base mid
>> (struct mid_q_entry) that indicates smb2 vs. cifs..
>>
>
> Why do even that? Why not a common mid struct that's simply a little larger?
> Sure it means slightly more memory consumption, but we never have that many
> in flight. Something like:
>
> struct mid_q_entry {
> __u8 protocol_id;
> struct list_head qhead; /* mids waiting on reply from this server */
> int midState; /* wish this were enum but can not pass to wait_event
> */
> unsigned long when_alloc; /* when mid was created */
> #ifdef CONFIG_CIFS_STATS2
> unsigned long when_sent; /* time when smb send finished */
> unsigned long when_received; /* when demux complete (taken off wire) */
> #endif
> bool largeBuf:1; /* if valid response, is pointer to large buf
> */
> void *resp_buf; /* response buffer */
> mid_callback_t *callback; /* call completion callback */
> void *callback_data; /* general purpose pointer for callback */
> __u64 mid; /* multiplex id */
> __le16 command; /* command code */
> __u32 pid; /* process id */
> __u32 sequence_number; /* for CIFS signing */
> bool multiRsp:1; /* multiple trans2 responses for one request
> */
> bool multiEnd:1; /* both received */
> };
>
> Using different structs here means that you need an entirely different
> set of code to deal with them. IMO, the memory savings (if any) isn't
> worth the duplicate code that'll be necessary.
>
When we need to work only with common field we can always assign it to
a common mid_q_entry pointer and work with it. But when we need to
work with protocol dependent fields we will do check like (in both
variants - yours and mine)
if (protocol == SMB2)
smb2_func
else
cifs_func
So, we don't need entirely different set of code. We will have common
routines as well as cifs and smb2 specific ones. It seems that you
suggest the same - I understand so. Please, sorry me, if I am
mistaken.
--
Best regards,
Pavel Shilovsky.
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