17 марта 2012 г. 14:32 пользователь Jeff Layton <jlayton@xxxxxxxxxx> написал:
> On Fri, 16 Mar 2012 18:09:26 +0300
> Pavel Shilovsky <piastry@xxxxxxxxxxx> wrote:
>
>> and send no more than credits value requests at once. For SMB/CIFS
>> it's trivial: increment this value by receiving any message and
>> decrement by sending one.
>>
>
> The existing code essentially "hardcodes" a value of 50 instead of
> using maxReq. While I think that's wrong, if you change that behavior
> in the first patch, it's going to make tracking down any regressions
> from this very difficult.
>
> I think it might be better to have this series introduce no behavioral
> changes at all, and simply reorganize the code around a credit-based
> model. Once that's complete and working, then do a patch that makes the
> code respect maxReq.
>
> I know that that's more work, but we do need to be careful when we're
> tinkering with the low-level plumbing like this...
>
>> Signed-off-by: Pavel Shilovsky <piastry@xxxxxxxxxxx>
>> ---
>> fs/cifs/cifsglob.h | 11 +++++++----
>> fs/cifs/cifsproto.h | 3 +++
>> fs/cifs/cifssmb.c | 10 +++++-----
>> fs/cifs/connect.c | 14 ++++++--------
>> fs/cifs/misc.c | 18 ++++++++++++++++++
>> fs/cifs/transport.c | 36 ++++++++++++++++++++----------------
>> 6 files changed, 59 insertions(+), 33 deletions(-)
>>
>> diff --git a/fs/cifs/cifsglob.h b/fs/cifs/cifsglob.h
>> index fb78bc9..d55de96 100644
>> --- a/fs/cifs/cifsglob.h
>> +++ b/fs/cifs/cifsglob.h
>> @@ -250,8 +250,9 @@ struct TCP_Server_Info {
>> bool noblocksnd; /* use blocking sendmsg */
>> bool noautotune; /* do not autotune send buf sizes */
>> bool tcp_nodelay;
>> + int credits; /* send no more requests at once */
>> unsigned int in_flight; /* number of requests on the wire to server */
>> - spinlock_t req_lock; /* protect the value above */
>> + spinlock_t req_lock; /* protect the two values above */
>> struct mutex srv_mutex;
>> struct task_struct *tsk;
>> char server_GUID[16];
>> @@ -314,12 +315,14 @@ in_flight(struct TCP_Server_Info *server)
>> return num;
>> }
>>
>> -static inline void
>> -dec_in_flight(struct TCP_Server_Info *server)
>> +static inline bool
>> +has_credits(struct TCP_Server_Info *server)
>> {
>> + int num;
>> spin_lock(&server->req_lock);
>> - server->in_flight--;
>> + num = server->credits;
>> spin_unlock(&server->req_lock);
>> + return num > 0;
>> }
>>
>> /*
>> diff --git a/fs/cifs/cifsproto.h b/fs/cifs/cifsproto.h
>> index 6f4e243..47a769e 100644
>> --- a/fs/cifs/cifsproto.h
>> +++ b/fs/cifs/cifsproto.h
>> @@ -88,6 +88,9 @@ extern int SendReceiveBlockingLock(const unsigned int xid,
>> struct smb_hdr *in_buf ,
>> struct smb_hdr *out_buf,
>> int *bytes_returned);
>> +extern void cifs_add_credits(struct TCP_Server_Info *server,
>> + const unsigned int add);
>> +extern void cifs_set_credits(struct TCP_Server_Info *server, const int val);
>> extern int checkSMB(struct smb_hdr *smb, __u16 mid, unsigned int length);
>> extern bool is_valid_oplock_break(struct smb_hdr *smb,
>> struct TCP_Server_Info *);
>> diff --git a/fs/cifs/cifssmb.c b/fs/cifs/cifssmb.c
>> index d7cbcfa..08c84a1 100644
>> --- a/fs/cifs/cifssmb.c
>> +++ b/fs/cifs/cifssmb.c
>> @@ -461,7 +461,7 @@ CIFSSMBNegotiate(unsigned int xid, struct cifs_ses *ses)
>> server->maxReq = min_t(unsigned int,
>> le16_to_cpu(rsp->MaxMpxCount),
>> cifs_max_pending);
>> - server->oplocks = server->maxReq > 1 ? enable_oplocks : false;
>> + cifs_set_credits(server, server->maxReq);
>> server->maxBuf = le16_to_cpu(rsp->MaxBufSize);
>> server->max_vcs = le16_to_cpu(rsp->MaxNumberVcs);
>> /* even though we do not use raw we might as well set this
>> @@ -569,7 +569,7 @@ CIFSSMBNegotiate(unsigned int xid, struct cifs_ses *ses)
>> little endian */
>> server->maxReq = min_t(unsigned int, le16_to_cpu(pSMBr->MaxMpxCount),
>> cifs_max_pending);
>> - server->oplocks = server->maxReq > 1 ? enable_oplocks : false;
>> + cifs_set_credits(server, server->maxReq);
>> /* probably no need to store and check maxvcs */
>> server->maxBuf = le32_to_cpu(pSMBr->MaxBufferSize);
>> server->max_rw = le32_to_cpu(pSMBr->MaxRawSize);
>> @@ -721,7 +721,7 @@ cifs_echo_callback(struct mid_q_entry *mid)
>> struct TCP_Server_Info *server = mid->callback_data;
>>
>> DeleteMidQEntry(mid);
>> - dec_in_flight(server);
>> + cifs_add_credits(server, 1);
>> wake_up(&server->request_q);
> ^^^^^^^^^
>
> The above wake_up always follows the call to cifs_add_credits. Should
> you go ahead and move it inside of cifs_add_credits?
That makes sense - will fix it when we decide what to do with the first patch.
>
>
>> }
>>
>> @@ -1674,7 +1674,7 @@ cifs_readv_callback(struct mid_q_entry *mid)
>>
>> queue_work(system_nrt_wq, &rdata->work);
>> DeleteMidQEntry(mid);
>> - dec_in_flight(server);
>> + cifs_add_credits(server, 1);
>> wake_up(&server->request_q);
>> }
>>
>> @@ -2115,7 +2115,7 @@ cifs_writev_callback(struct mid_q_entry *mid)
>>
>> queue_work(system_nrt_wq, &wdata->work);
>> DeleteMidQEntry(mid);
>> - dec_in_flight(tcon->ses->server);
>> + cifs_add_credits(tcon->ses->server, 1);
>> wake_up(&tcon->ses->server->request_q);
>> }
>>
>> diff --git a/fs/cifs/connect.c b/fs/cifs/connect.c
>> index a7627f2..f3a0c49 100644
>> --- a/fs/cifs/connect.c
>> +++ b/fs/cifs/connect.c
>> @@ -642,14 +642,10 @@ static void clean_demultiplex_info(struct TCP_Server_Info *server)
>> spin_unlock(&GlobalMid_Lock);
>> wake_up_all(&server->response_q);
>>
>> - /* Check if we have blocked requests that need to free. */
>> + /* check if we have blocked requests that need to free */
>> spin_lock(&server->req_lock);
>> - if (server->in_flight >= server->maxReq)
>> - server->in_flight = server->maxReq - 1;
>> - /*
>> - * We do not want to set the max_pending too low or we could end up
>> - * with the counter going negative.
>> - */
>> + if (server->credits <= 0)
>> + server->credits = 1;
>> spin_unlock(&server->req_lock);
>> /*
>> * Although there should not be any requests blocked on this queue it
>> @@ -1906,7 +1902,7 @@ cifs_get_tcp_session(struct smb_vol *volume_info)
>> tcp_ses->noautotune = volume_info->noautotune;
>> tcp_ses->tcp_nodelay = volume_info->sockopt_tcp_nodelay;
>> tcp_ses->in_flight = 0;
>> - tcp_ses->maxReq = 1; /* enough to send negotiate request */
>> + tcp_ses->credits = 1;
>> init_waitqueue_head(&tcp_ses->response_q);
>> init_waitqueue_head(&tcp_ses->request_q);
>> INIT_LIST_HEAD(&tcp_ses->pending_mid_q);
>> @@ -3756,9 +3752,11 @@ int cifs_negotiate_protocol(unsigned int xid, struct cifs_ses *ses)
>> if (server->maxBuf != 0)
>> return 0;
>>
>> + cifs_set_credits(server, 1);
>> rc = CIFSSMBNegotiate(xid, ses);
>> if (rc == -EAGAIN) {
>> /* retry only once on 1st time connection */
>> + cifs_set_credits(server, 1);
>> rc = CIFSSMBNegotiate(xid, ses);
>> if (rc == -EAGAIN)
>> rc = -EHOSTDOWN;
>> diff --git a/fs/cifs/misc.c b/fs/cifs/misc.c
>> index 703ef5c..5dc936b 100644
>> --- a/fs/cifs/misc.c
>> +++ b/fs/cifs/misc.c
>> @@ -690,3 +690,21 @@ backup_cred(struct cifs_sb_info *cifs_sb)
>>
>> return false;
>> }
>> +
>> +void
>> +cifs_add_credits(struct TCP_Server_Info *server, const unsigned int add)
>> +{
>> + spin_lock(&server->req_lock);
>> + server->credits += add;
>> + server->in_flight--;
>> + spin_unlock(&server->req_lock);
>> +}
>> +
>> +void
>> +cifs_set_credits(struct TCP_Server_Info *server, const int val)
>> +{
>> + spin_lock(&server->req_lock);
>> + server->credits = val;
>> + server->oplocks = val > 1 ? enable_oplocks : false;
>> + spin_unlock(&server->req_lock);
>> +}
>> diff --git a/fs/cifs/transport.c b/fs/cifs/transport.c
>> index e2673aa..e8a4fd3 100644
>> --- a/fs/cifs/transport.c
>> +++ b/fs/cifs/transport.c
>> @@ -262,16 +262,16 @@ wait_for_free_request(struct TCP_Server_Info *server, const int long_op)
>> if (long_op == CIFS_ASYNC_OP) {
>> /* oplock breaks must not be held up */
>> server->in_flight++;
>> + server->credits--;
>> spin_unlock(&server->req_lock);
>> return 0;
>> }
>>
>> while (1) {
>> - if (server->in_flight >= server->maxReq) {
>> + if (server->credits <= 0) {
>> spin_unlock(&server->req_lock);
>> cifs_num_waiters_inc(server);
>> - wait_event(server->request_q,
>> - in_flight(server) < server->maxReq);
>> + wait_event(server->request_q, has_credits(server));
>> cifs_num_waiters_dec(server);
>> spin_lock(&server->req_lock);
>> } else {
>> @@ -280,12 +280,16 @@ wait_for_free_request(struct TCP_Server_Info *server, const int long_op)
>> return -ENOENT;
>> }
>>
>> - /* can not count locking commands against total
>> - as they are allowed to block on server */
>> + /*
>> + * Can not count locking commands against total
>> + * as they are allowed to block on server.
>> + */
>>
>> /* update # of requests on the wire to server */
>> - if (long_op != CIFS_BLOCKING_OP)
>> + if (long_op != CIFS_BLOCKING_OP) {
>> + server->credits--;
>> server->in_flight++;
>> + }
>> spin_unlock(&server->req_lock);
>> break;
>> }
>> @@ -360,7 +364,7 @@ cifs_call_async(struct TCP_Server_Info *server, struct kvec *iov,
>> mid = AllocMidQEntry(hdr, server);
>> if (mid == NULL) {
>> mutex_unlock(&server->srv_mutex);
>> - dec_in_flight(server);
>> + cifs_add_credits(server, 1);
>> wake_up(&server->request_q);
>> return -ENOMEM;
>> }
>> @@ -393,7 +397,7 @@ cifs_call_async(struct TCP_Server_Info *server, struct kvec *iov,
>> return rc;
>> out_err:
>> delete_mid(mid);
>> - dec_in_flight(server);
>> + cifs_add_credits(server, 1);
>> wake_up(&server->request_q);
>> return rc;
>> }
>> @@ -565,7 +569,7 @@ SendReceive2(const unsigned int xid, struct cifs_ses *ses,
>> mutex_unlock(&ses->server->srv_mutex);
>> cifs_small_buf_release(in_buf);
>> /* Update # of requests on wire to server */
>> - dec_in_flight(ses->server);
>> + cifs_add_credits(ses->server, 1);
>> wake_up(&ses->server->request_q);
>> return rc;
>> }
>> @@ -602,7 +606,7 @@ SendReceive2(const unsigned int xid, struct cifs_ses *ses,
>> midQ->callback = DeleteMidQEntry;
>> spin_unlock(&GlobalMid_Lock);
>> cifs_small_buf_release(in_buf);
>> - dec_in_flight(ses->server);
>> + cifs_add_credits(ses->server, 1);
>> wake_up(&ses->server->request_q);
>> return rc;
>> }
>> @@ -613,7 +617,7 @@ SendReceive2(const unsigned int xid, struct cifs_ses *ses,
>>
>> rc = cifs_sync_mid_result(midQ, ses->server);
>> if (rc != 0) {
>> - dec_in_flight(ses->server);
>> + cifs_add_credits(ses->server, 1);
>> wake_up(&ses->server->request_q);
>> return rc;
>> }
>> @@ -638,7 +642,7 @@ SendReceive2(const unsigned int xid, struct cifs_ses *ses,
>> midQ->resp_buf = NULL;
>> out:
>> delete_mid(midQ);
>> - dec_in_flight(ses->server);
>> + cifs_add_credits(ses->server, 1);
>> wake_up(&ses->server->request_q);
>>
>> return rc;
>> @@ -689,7 +693,7 @@ SendReceive(const unsigned int xid, struct cifs_ses *ses,
>> if (rc) {
>> mutex_unlock(&ses->server->srv_mutex);
>> /* Update # of requests on wire to server */
>> - dec_in_flight(ses->server);
>> + cifs_add_credits(ses->server, 1);
>> wake_up(&ses->server->request_q);
>> return rc;
>> }
>> @@ -722,7 +726,7 @@ SendReceive(const unsigned int xid, struct cifs_ses *ses,
>> /* no longer considered to be "in-flight" */
>> midQ->callback = DeleteMidQEntry;
>> spin_unlock(&GlobalMid_Lock);
>> - dec_in_flight(ses->server);
>> + cifs_add_credits(ses->server, 1);
>> wake_up(&ses->server->request_q);
>> return rc;
>> }
>> @@ -731,7 +735,7 @@ SendReceive(const unsigned int xid, struct cifs_ses *ses,
>>
>> rc = cifs_sync_mid_result(midQ, ses->server);
>> if (rc != 0) {
>> - dec_in_flight(ses->server);
>> + cifs_add_credits(ses->server, 1);
>> wake_up(&ses->server->request_q);
>> return rc;
>> }
>> @@ -748,7 +752,7 @@ SendReceive(const unsigned int xid, struct cifs_ses *ses,
>> rc = cifs_check_receive(midQ, ses->server, 0);
>> out:
>> delete_mid(midQ);
>> - dec_in_flight(ses->server);
>> + cifs_add_credits(ses->server, 1);
>> wake_up(&ses->server->request_q);
>>
>> return rc;
>
> --
> Jeff Layton <jlayton@xxxxxxxxxx>
--
Best regards,
Pavel Shilovsky.
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