On Fri, 28 Oct 2011 23:54:16 +0400
Pavel Shilovsky <piastry@xxxxxxxxxxx> wrote:
> From: Steve French <sfrench@xxxxxxxxxx>
>
> wait_for_free_request is called to ensure that we don't have more than the
> configured maximum of requests in flight on the wire (for cifs), but for SMB2,
> the number of requests that can be in flight varies dynamically (the client
> may request that the server grant more "credits" in a request, and each
> request uses at least one credit). Instead of migrating over the original
> smb2_wait_for_free_request function, simply add a check in cifs's original
> wait_for_free_request for the is_smb2 case to make sure that we don't go
> beyond the number of allocated "credits" (ie those that remain from those
> the server has allocated for this tcp session). Otherwise the logic is unchanged
> (other than to make it extern so that the next function to be added, smb2_sendrcv2
> in smbtransport.c can call it - smb2_sendrcv2 will be migrated over in the next patch).
>
> Note that smb2 servers will typically allow many more requests in flight at one time
> than cifs servers (which usually default to only 50) and can adjust this as needed.
> This should provide significant performance benefit in some workloads (ie smb2
> in many cases will get more parallelism than cifs and some other protocols
> since some artificially constrain the maximum number of requests).
>
> Signed-off-by: Steve French <sfrench@xxxxxxxxxx>
> Signed-off-by: Pavel Shilovsky <piastry@xxxxxxxxxxx>
> ---
> fs/cifs/cifsglob.h | 1 +
> fs/cifs/cifsproto.h | 3 ++-
> fs/cifs/transport.c | 22 +++++++++++++++++++---
> 3 files changed, 22 insertions(+), 4 deletions(-)
>
> diff --git a/fs/cifs/cifsglob.h b/fs/cifs/cifsglob.h
> index 179b784..b440329 100644
> --- a/fs/cifs/cifsglob.h
> +++ b/fs/cifs/cifsglob.h
> @@ -311,6 +311,7 @@ struct TCP_Server_Info {
> wait_queue_head_t read_q; /* used by readpages */
> atomic_t active_readpage_req; /* used by readpages */
> atomic_t resp_rdy; /* used by readpages and demultiplex */
> + atomic_t credits; /* send no more simultaneous requests than this */
> __le16 smb2_dialect_revision; /* SMB2.0 implemented, 2.1 recognized */
> struct task_struct *observe;
> char smb2_crypt_key[CIFS_CRYPTO_KEY_SIZE]; /* BB can we use cifs key */
> diff --git a/fs/cifs/cifsproto.h b/fs/cifs/cifsproto.h
> index ef4f631..84d1e4c 100644
> --- a/fs/cifs/cifsproto.h
> +++ b/fs/cifs/cifsproto.h
> @@ -1,7 +1,7 @@
> /*
> * fs/cifs/cifsproto.h
> *
> - * Copyright (c) International Business Machines Corp., 2002,2008
> + * Copyright (c) International Business Machines Corp., 2002,2011
> * Author(s): Steve French (sfrench@xxxxxxxxxx)
> *
> * This library is free software; you can redistribute it and/or modify
> @@ -68,6 +68,7 @@ extern char *cifs_compose_mount_options(const char *sb_mountdata,
> extern struct mid_q_entry *AllocMidQEntry(const struct smb_hdr *smb_buffer,
> struct TCP_Server_Info *server);
> extern void DeleteMidQEntry(struct mid_q_entry *midEntry);
> +extern int wait_for_free_request(struct TCP_Server_Info *sv, const int long_op);
> extern int cifs_call_async(struct TCP_Server_Info *server, struct kvec *iov,
> unsigned int nvec, mid_receive_t *receive,
> mid_callback_t *callback, void *cbdata,
> diff --git a/fs/cifs/transport.c b/fs/cifs/transport.c
> index 0cc9584..25d04df 100644
> --- a/fs/cifs/transport.c
> +++ b/fs/cifs/transport.c
> @@ -254,7 +254,7 @@ 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,
> +int wait_for_free_request(struct TCP_Server_Info *server,
> const int long_op)
> {
> if (long_op == CIFS_ASYNC_OP) {
> @@ -265,7 +265,8 @@ static int wait_for_free_request(struct TCP_Server_Info *server,
>
> spin_lock(&GlobalMid_Lock);
> while (1) {
> - if (atomic_read(&server->inFlight) >= cifs_max_pending) {
> + if ((server->is_smb2 == false) &&
> + atomic_read(&server->inFlight) >= cifs_max_pending) {
> spin_unlock(&GlobalMid_Lock);
> cifs_num_waiters_inc(server);
> wait_event(server->request_q,
> @@ -273,6 +274,16 @@ static int wait_for_free_request(struct TCP_Server_Info *server,
> < cifs_max_pending);
> cifs_num_waiters_dec(server);
> spin_lock(&GlobalMid_Lock);
> +#ifdef CONFIG_CIFS_SMB2
> + } else if (server->is_smb2 &&
> + (atomic_read(&server->credits) < 1)) {
> + spin_unlock(&GlobalMid_Lock);
> + cifs_num_waiters_inc(server);
> + wait_event(server->request_q,
> + atomic_read(&server->credits) > 0);
> + cifs_num_waiters_dec(server);
> + spin_lock(&GlobalMid_Lock);
> +#endif /* CONFIG_CIFS_SMB2 */
> } else {
> if (server->tcpStatus == CifsExiting) {
> spin_unlock(&GlobalMid_Lock);
> @@ -283,8 +294,13 @@ static int wait_for_free_request(struct TCP_Server_Info *server,
> as they are allowed to block on server */
>
> /* update # of requests on the wire to server */
> - if (long_op != CIFS_BLOCKING_OP)
> + if (server->is_smb2 == false &&
> + long_op != CIFS_BLOCKING_OP)
> atomic_inc(&server->inFlight);
> +#ifdef CONFIG_CIFS_SMB2
> + else if (server->is_smb2)
> + atomic_dec(&server->credits);
> +#endif
> spin_unlock(&GlobalMid_Lock);
> break;
> }
This patch doesn't make much sense...
"credits" gets initialized to 0, then on the first request, you'll
decrement it which will make it go negative. I then don't see any place
where credits is ever incremented.
Maybe that happens in a different patch, but splitting your patches out
this way makes no sense. No one can reasonably review this patch for
sanity since the lifecycle of "credits" is incomplete.
--
Jeff Layton <jlayton@xxxxxxxxx>
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