2011/10/29 Jeff Layton <jlayton@xxxxxxxxx>:
> 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.
In this case we should move this patch after we add smb2_sendrcv
function (where credits are increased). Make sense?
--
Best regards,
Pavel Shilovsky.
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