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?
> }
>
> @@ -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>
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