[linux-cifs] Re: [PATCH 01/11] CIFS: Simplify inFlight logic


I got a chance to look through this patch set in more detail on the way
to the SMB2.2 test event.  I liked many of the patches, but this one
seems to complicate, rather than simplify by adding a spinlock
to what used to be an atomic_inc.  There is also a possibility that this
spinlock will become hot.  I don't mind moving the atomic_inc inside the
new dec_in_flight macro though to make it easier in the future.

On Wed, Feb 22, 2012 at 1:32 AM, Pavel Shilovsky  wrote:
> by making it as unsigned integer and surround access with req_lock
> from server structure.
>
> Signed-off-by: Pavel Shilovsky 
> ---
> fs/cifs/cifs_debug.c |  3 +--
> fs/cifs/cifsglob.h  |  21 ++++++++++++++++++++-
> fs/cifs/cifssmb.c  |  6 +++---
> fs/cifs/connect.c  |  10 +++++-----
> fs/cifs/transport.c |  45 +++++++++++++++++++++++----------------------
> 5 files changed, 52 insertions(+), 33 deletions(-)
>
> diff --git a/fs/cifs/cifs_debug.c b/fs/cifs/cifs_debug.c
> index 24b3dfc..573b899 100644
> --- a/fs/cifs/cifs_debug.c
> +++ b/fs/cifs/cifs_debug.c
> @@ -171,8 +171,7 @@ static int cifs_debug_data_proc_show(struct seq_file *m, void *v)
>            seq_printf(m, "TCP status: %d\n\tLocal Users To "
>                  "Server: %d SecMode: 0x%x Req On Wire: %d",
>                  server->tcpStatus, server->srv_count,
> -                 server->sec_mode,
> -                 atomic_read(&server->inFlight));
> +                 server->sec_mode, in_flight(server));
>
> #ifdef CONFIG_CIFS_STATS2
>            seq_printf(m, " In Send: %d In MaxReq Wait: %d",
> diff --git a/fs/cifs/cifsglob.h b/fs/cifs/cifsglob.h
> index 76e7d8b..44cfc9a 100644
> --- a/fs/cifs/cifsglob.h
> +++ b/fs/cifs/cifsglob.h
> @@ -255,7 +255,8 @@ struct TCP_Server_Info {
>    bool noblocksnd;        /* use blocking sendmsg */
>    bool noautotune;        /* do not autotune send buf sizes */
>    bool tcp_nodelay;
> -    atomic_t inFlight; /* number of requests on the wire to server */
> +    unsigned int in_flight; /* number of requests on the wire to server */
> +    spinlock_t req_lock; /* protect the value above */
>    struct mutex srv_mutex;
>    struct task_struct *tsk;
>    char server_GUID[16];
> @@ -307,6 +308,24 @@ struct TCP_Server_Info {
> #endif
> };
>
> +static inline unsigned int
> +in_flight(struct TCP_Server_Info *server)
> +{
> +    unsigned int num;
> +    spin_lock(&server->req_lock);
> +    num = server->in_flight;
> +    spin_unlock(&server->req_lock);
> +    return num;
> +}
> +
> +static inline void
> +dec_in_flight(struct TCP_Server_Info *server)
> +{
> +    spin_lock(&server->req_lock);
> +    server->in_flight--;
> +    spin_unlock(&server->req_lock);
> +}
> +
> /*
> * Macros to allow the TCP_Server_Info->net field and related code to drop out
> * when CONFIG_NET_NS isn't set.
> diff --git a/fs/cifs/cifssmb.c b/fs/cifs/cifssmb.c
> index 8b7794c..0b50551 100644
> --- a/fs/cifs/cifssmb.c
> +++ b/fs/cifs/cifssmb.c
> @@ -716,7 +716,7 @@ cifs_echo_callback(struct mid_q_entry *mid)
>    struct TCP_Server_Info *server = mid->callback_data;
>
>    DeleteMidQEntry(mid);
> -    atomic_dec(&server->inFlight);
> +    dec_in_flight(server);
>    wake_up(&server->request_q);
> }
>
> @@ -1669,7 +1669,7 @@ cifs_readv_callback(struct mid_q_entry *mid)
>
>    queue_work(system_nrt_wq, &rdata->work);
>    DeleteMidQEntry(mid);
> -    atomic_dec(&server->inFlight);
> +    dec_in_flight(server);
>    wake_up(&server->request_q);
> }
>
> @@ -2110,7 +2110,7 @@ cifs_writev_callback(struct mid_q_entry *mid)
>
>    queue_work(system_nrt_wq, &wdata->work);
>    DeleteMidQEntry(mid);
> -    atomic_dec(&tcon->ses->server->inFlight);
> +    dec_in_flight(tcon->ses->server);
>    wake_up(&tcon->ses->server->request_q);
> }
>
> diff --git a/fs/cifs/connect.c b/fs/cifs/connect.c
> index 602f77c..12286d0 100644
> --- a/fs/cifs/connect.c
> +++ b/fs/cifs/connect.c
> @@ -647,14 +647,14 @@ static void clean_demultiplex_info(struct TCP_Server_Info *server)
>     * cifs_max_pending is normally 50, but can be set at module install
>     * time to as little as two.
>     */
> -    spin_lock(&GlobalMid_Lock);
> -    if (atomic_read(&server->inFlight) >= cifs_max_pending)
> -        atomic_set(&server->inFlight, cifs_max_pending - 1);
> +    spin_lock(&server->req_lock);
> +    if (server->in_flight >= cifs_max_pending)
> +        server->in_flight = cifs_max_pending - 1;
>    /*
>     * We do not want to set the max_pending too low or we could end up
>     * with the counter going negative.
>     */
> -    spin_unlock(&GlobalMid_Lock);
> +    spin_unlock(&server->req_lock);
>    /*
>     * Although there should not be any requests blocked on this queue it
>     * can not hurt to be paranoid and try to wake up requests that may
> @@ -1909,7 +1909,7 @@ cifs_get_tcp_session(struct smb_vol *volume_info)
>    tcp_ses->noblocksnd = volume_info->noblocksnd;
>    tcp_ses->noautotune = volume_info->noautotune;
>    tcp_ses->tcp_nodelay = volume_info->sockopt_tcp_nodelay;
> -    atomic_set(&tcp_ses->inFlight, 0);
> +    tcp_ses->in_flight = 0;
>    init_waitqueue_head(&tcp_ses->response_q);
>    init_waitqueue_head(&tcp_ses->request_q);
>    INIT_LIST_HEAD(&tcp_ses->pending_mid_q);
> diff --git a/fs/cifs/transport.c b/fs/cifs/transport.c
> index 0cc9584..fc1904f 100644
> --- a/fs/cifs/transport.c
> +++ b/fs/cifs/transport.c
> @@ -254,28 +254,29 @@ smb_send(struct TCP_Server_Info *server, struct smb_hdr *smb_buffer,
>    return smb_sendv(server, &iov, 1);
> }
>
> -static int wait_for_free_request(struct TCP_Server_Info *server,
> -                const int long_op)
> +static int
> +wait_for_free_request(struct TCP_Server_Info *server, const int long_op)
> {
> +    spin_lock(&server->req_lock);
> +
>    if (long_op == CIFS_ASYNC_OP) {
>        /* oplock breaks must not be held up */
> -        atomic_inc(&server->inFlight);
> +        server->in_flight++;
> +        spin_unlock(&server->req_lock);
>        return 0;
>    }
>
> -    spin_lock(&GlobalMid_Lock);
>    while (1) {
> -        if (atomic_read(&server->inFlight) >= cifs_max_pending) {
> -            spin_unlock(&GlobalMid_Lock);
> +        if (server->in_flight >= cifs_max_pending) {
> +            spin_unlock(&server->req_lock);
>            cifs_num_waiters_inc(server);
>            wait_event(server->request_q,
> -                 atomic_read(&server->inFlight)
> -                  < cifs_max_pending);
> +                 in_flight(server) < cifs_max_pending);
>            cifs_num_waiters_dec(server);
> -            spin_lock(&GlobalMid_Lock);
> +            spin_lock(&server->req_lock);
>        } else {
>            if (server->tcpStatus == CifsExiting) {
> -                spin_unlock(&GlobalMid_Lock);
> +                spin_unlock(&server->req_lock);
>                return -ENOENT;
>            }
>
> @@ -284,8 +285,8 @@ static int wait_for_free_request(struct TCP_Server_Info *server,
>
>            /* update # of requests on the wire to server */
>            if (long_op != CIFS_BLOCKING_OP)
> -                atomic_inc(&server->inFlight);
> -            spin_unlock(&GlobalMid_Lock);
> +                server->in_flight++;
> +            spin_unlock(&server->req_lock);
>            break;
>        }
>    }
> @@ -359,7 +360,7 @@ cifs_call_async(struct TCP_Server_Info *server, struct kvec *iov,
>    mid = AllocMidQEntry(hdr, server);
>    if (mid == NULL) {
>        mutex_unlock(&server->srv_mutex);
> -        atomic_dec(&server->inFlight);
> +        dec_in_flight(server);
>        wake_up(&server->request_q);
>        return -ENOMEM;
>    }
> @@ -392,7 +393,7 @@ cifs_call_async(struct TCP_Server_Info *server, struct kvec *iov,
>    return rc;
> out_err:
>    delete_mid(mid);
> -    atomic_dec(&server->inFlight);
> +    dec_in_flight(server);
>    wake_up(&server->request_q);
>    return rc;
> }
> @@ -564,7 +565,7 @@ 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 */
> -        atomic_dec(&ses->server->inFlight);
> +        dec_in_flight(ses->server);
>        wake_up(&ses->server->request_q);
>        return rc;
>    }
> @@ -601,7 +602,7 @@ SendReceive2(const unsigned int xid, struct cifs_ses *ses,
>            midQ->callback = DeleteMidQEntry;
>            spin_unlock(&GlobalMid_Lock);
>            cifs_small_buf_release(in_buf);
> -            atomic_dec(&ses->server->inFlight);
> +            dec_in_flight(ses->server);
>            wake_up(&ses->server->request_q);
>            return rc;
>        }
> @@ -612,7 +613,7 @@ SendReceive2(const unsigned int xid, struct cifs_ses *ses,
>
>    rc = cifs_sync_mid_result(midQ, ses->server);
>    if (rc != 0) {
> -        atomic_dec(&ses->server->inFlight);
> +        dec_in_flight(ses->server);
>        wake_up(&ses->server->request_q);
>        return rc;
>    }
> @@ -637,7 +638,7 @@ SendReceive2(const unsigned int xid, struct cifs_ses *ses,
>        midQ->resp_buf = NULL;
> out:
>    delete_mid(midQ);
> -    atomic_dec(&ses->server->inFlight);
> +    dec_in_flight(ses->server);
>    wake_up(&ses->server->request_q);
>
>    return rc;
> @@ -688,7 +689,7 @@ SendReceive(const unsigned int xid, struct cifs_ses *ses,
>    if (rc) {
>        mutex_unlock(&ses->server->srv_mutex);
>        /* Update # of requests on wire to server */
> -        atomic_dec(&ses->server->inFlight);
> +        dec_in_flight(ses->server);
>        wake_up(&ses->server->request_q);
>        return rc;
>    }
> @@ -721,7 +722,7 @@ SendReceive(const unsigned int xid, struct cifs_ses *ses,
>            /* no longer considered to be "in-flight" */
>            midQ->callback = DeleteMidQEntry;
>            spin_unlock(&GlobalMid_Lock);
> -            atomic_dec(&ses->server->inFlight);
> +            dec_in_flight(ses->server);
>            wake_up(&ses->server->request_q);
>            return rc;
>        }
> @@ -730,7 +731,7 @@ SendReceive(const unsigned int xid, struct cifs_ses *ses,
>
>    rc = cifs_sync_mid_result(midQ, ses->server);
>    if (rc != 0) {
> -        atomic_dec(&ses->server->inFlight);
> +        dec_in_flight(ses->server);
>        wake_up(&ses->server->request_q);
>        return rc;
>    }
> @@ -747,7 +748,7 @@ SendReceive(const unsigned int xid, struct cifs_ses *ses,
>    rc = cifs_check_receive(midQ, ses->server, 0);
> out:
>    delete_mid(midQ);
> -    atomic_dec(&ses->server->inFlight);
> +    dec_in_flight(ses->server);
>    wake_up(&ses->server->request_q);
>
>    return rc;
> --
> 1.7.1
>
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-- 
Thanks,

Steve

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