On Mon, Mar 19, 2012 at 3:24 PM, Jeff Layton <jlayton@xxxxxxxxxx> wrote:
> On Fri, 16 Mar 2012 18:09:33 +0300
> Pavel Shilovsky <piastry@xxxxxxxxxxx> wrote:
>
>> While in CIFS/SMB we have 16 bit mid, in SMB2 it is 64 bit.
>> Convert the existing field to 64 bit and mask off higher bits
>> for CIFS/SMB.
>>
>> Signed-off-by: Pavel Shilovsky <piastry@xxxxxxxxxxx>
>> ---
>> fs/cifs/cifsglob.h | 2 +-
>> fs/cifs/cifsproto.h | 2 +-
>> fs/cifs/misc.c | 84 ++++++++++++++++++++++++++++-----------------------
>> 3 files changed, 48 insertions(+), 40 deletions(-)
>>
>> diff --git a/fs/cifs/cifsglob.h b/fs/cifs/cifsglob.h
>> index a403398..b213458 100644
>> --- a/fs/cifs/cifsglob.h
>> +++ b/fs/cifs/cifsglob.h
>> @@ -282,7 +282,7 @@ struct TCP_Server_Info {
>> vcnumbers */
>> int capabilities; /* allow selective disabling of caps by smb sess */
>> int timeAdj; /* Adjust for difference in server time zone in sec */
>> - __u16 CurrentMid; /* multiplex id - rotating counter */
>> + __u64 CurrentMid; /* multiplex id - rotating counter */
>
> It occurs to me that a simpler way to do this might be to turn this
> into a union with a u16 and u64 field. This works just as well though...
>
>> char cryptkey[CIFS_CRYPTO_KEY_SIZE]; /* used by ntlm, ntlmv2 etc */
>> /* 16th byte of RFC1001 workstation name is always null */
>> char workstation_RFC1001_name[RFC1001_NAME_LEN_WITH_NULL];
>> diff --git a/fs/cifs/cifsproto.h b/fs/cifs/cifsproto.h
>> index db38a40..8958721 100644
>> --- a/fs/cifs/cifsproto.h
>> +++ b/fs/cifs/cifsproto.h
>> @@ -115,7 +115,7 @@ extern int small_smb_init_no_tc(const int smb_cmd, const int wct,
>> void **request_buf);
>> extern int CIFS_SessSetup(unsigned int xid, struct cifs_ses *ses,
>> const struct nls_table *nls_cp);
>> -extern __u16 GetNextMid(struct TCP_Server_Info *server);
>> +extern __u64 GetNextMid(struct TCP_Server_Info *server);
>> extern struct timespec cifs_NTtimeToUnix(__le64 utc_nanoseconds_since_1601);
>> extern u64 cifs_UnixTimeToNT(struct timespec);
>> extern struct timespec cnvrtDosUnixTm(__le16 le_date, __le16 le_time,
>> diff --git a/fs/cifs/misc.c b/fs/cifs/misc.c
>> index 88459d0..0b743b7 100644
>> --- a/fs/cifs/misc.c
>> +++ b/fs/cifs/misc.c
>> @@ -213,54 +213,61 @@ cifs_small_buf_release(void *buf_to_free)
>> }
>>
>> /*
>> - Find a free multiplex id (SMB mid). Otherwise there could be
>> - mid collisions which might cause problems, demultiplexing the
>> - wrong response to this request. Multiplex ids could collide if
>> - one of a series requests takes much longer than the others, or
>> - if a very large number of long lived requests (byte range
>> - locks or FindNotify requests) are pending. No more than
>> - 64K-1 requests can be outstanding at one time. If no
>> - mids are available, return zero. A future optimization
>> - could make the combination of mids and uid the key we use
>> - to demultiplex on (rather than mid alone).
>> - In addition to the above check, the cifs demultiplex
>> - code already used the command code as a secondary
>> - check of the frame and if signing is negotiated the
>> - response would be discarded if the mid were the same
>> - but the signature was wrong. Since the mid is not put in the
>> - pending queue until later (when it is about to be dispatched)
>> - we do have to limit the number of outstanding requests
>> - to somewhat less than 64K-1 although it is hard to imagine
>> - so many threads being in the vfs at one time.
>> -*/
>> -__u16 GetNextMid(struct TCP_Server_Info *server)
>> + * Find a free multiplex id (SMB mid). Otherwise there could be
>> + * mid collisions which might cause problems, demultiplexing the
>> + * wrong response to this request. Multiplex ids could collide if
>> + * one of a series requests takes much longer than the others, or
>> + * if a very large number of long lived requests (byte range
>> + * locks or FindNotify requests) are pending. No more than
>> + * 64K-1 requests can be outstanding at one time. If no
>> + * mids are available, return zero. A future optimization
>> + * could make the combination of mids and uid the key we use
>> + * to demultiplex on (rather than mid alone).
>> + * In addition to the above check, the cifs demultiplex
>> + * code already used the command code as a secondary
>> + * check of the frame and if signing is negotiated the
>> + * response would be discarded if the mid were the same
>> + * but the signature was wrong. Since the mid is not put in the
>> + * pending queue until later (when it is about to be dispatched)
>> + * we do have to limit the number of outstanding requests
>> + * to somewhat less than 64K-1 although it is hard to imagine
>> + * so many threads being in the vfs at one time.
>> + */
>> +__u64 GetNextMid(struct TCP_Server_Info *server)
>> {
>> - __u16 mid = 0;
>> - __u16 last_mid;
>> + __u64 mid = 0;
>> + __u16 last_mid, cur_mid;
>> bool collision;
>>
>> spin_lock(&GlobalMid_Lock);
>> - last_mid = server->CurrentMid; /* we do not want to loop forever */
>> - server->CurrentMid++;
>> - /* This nested loop looks more expensive than it is.
>> - In practice the list of pending requests is short,
>> - fewer than 50, and the mids are likely to be unique
>> - on the first pass through the loop unless some request
>> - takes longer than the 64 thousand requests before it
>> - (and it would also have to have been a request that
>> - did not time out) */
>> - while (server->CurrentMid != last_mid) {
>> +
>> + /* mid is 16 bit only for CIFS/SMB */
>> + cur_mid = (__u16)((server->CurrentMid) & 0xffff);
>> + /* we do not want to loop forever */
>> + last_mid = cur_mid;
>> + cur_mid++;
>> +
>> + /*
>> + * This nested loop looks more expensive than it is.
>> + * In practice the list of pending requests is short,
>> + * fewer than 50, and the mids are likely to be unique
>> + * on the first pass through the loop unless some request
>> + * takes longer than the 64 thousand requests before it
>> + * (and it would also have to have been a request that
>> + * did not time out).
>> + */
>> + while (cur_mid != last_mid) {
>> struct mid_q_entry *mid_entry;
>> unsigned int num_mids;
>>
>> collision = false;
>> - if (server->CurrentMid == 0)
>> - server->CurrentMid++;
>> + if (cur_mid == 0)
>> + cur_mid++;
>>
>> num_mids = 0;
>> list_for_each_entry(mid_entry, &server->pending_mid_q, qhead) {
>> ++num_mids;
>> - if (mid_entry->mid == server->CurrentMid &&
>> + if (mid_entry->mid == cur_mid &&
>> mid_entry->midState == MID_REQUEST_SUBMITTED) {
>> /* This mid is in use, try a different one */
>> collision = true;
>> @@ -282,10 +289,11 @@ __u16 GetNextMid(struct TCP_Server_Info *server)
>> server->tcpStatus = CifsNeedReconnect;
>>
>> if (!collision) {
>> - mid = server->CurrentMid;
>> + mid = (__u64)cur_mid;
>> + server->CurrentMid = mid;
>> break;
>> }
>> - server->CurrentMid++;
>> + cur_mid++;
>> }
>> spin_unlock(&GlobalMid_Lock);
>> return mid;
>
> Not directly related to this patch, but should we move all of these mid
> operations under the req_lock instead of the GlobalMid_Lock? The global
> spinlock is a bottleneck and all of the structures involved should be
> per-server anyway.
>
> Anyway, I think this looks ok
>
> Reviewed-by: Jeff Layton <jlayton@xxxxxxxxxx>
The idea of a union for these two key fields is worth thinking about
more - any more opinions from others on this?
--
Thanks,
Steve
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