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From: Chuck Lever III <chuck.lever@oracle.com>
To: Trond Myklebust <trondmy@hammerspace.com>
Cc: Linux NFS Mailing List <linux-nfs@vger.kernel.org>,
	"linux-rdma@vger.kernel.org" <linux-rdma@vger.kernel.org>
Subject: Re: [PATCH v3 07/26] xprtrdma: Improve locking around rpcrdma_rep destruction
Date: Sat, 24 Apr 2021 17:39:15 +0000
Message-ID: <0DA1937B-3EA1-45A9-BD37-F7426764F83D@oracle.com> (raw)
In-Reply-To: <89d2e2bbc40d953e28c4e4d56be0b5c83c25dc23.camel@hammerspace.com>



> On Apr 23, 2021, at 5:06 PM, Trond Myklebust <trondmy@hammerspace.com> wrote:
> 
> On Mon, 2021-04-19 at 14:02 -0400, Chuck Lever wrote:
>> Currently rpcrdma_reps_destroy() assumes that, at transport
>> tear-down, the content of the rb_free_reps list is the same as the
>> content of the rb_all_reps list. Although that is usually true,
>> using the rb_all_reps list should be more reliable because of
>> the way it's managed. And, rpcrdma_reps_unmap() uses rb_all_reps;
>> these two functions should both traverse the "all" list.
>> 
>> Ensure that all rpcrdma_reps are always destroyed whether they are
>> on the rep free list or not.
>> 
>> Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
>> ---
>>  net/sunrpc/xprtrdma/verbs.c |   31 ++++++++++++++++++++++++-------
>>  1 file changed, 24 insertions(+), 7 deletions(-)
>> 
>> diff --git a/net/sunrpc/xprtrdma/verbs.c
>> b/net/sunrpc/xprtrdma/verbs.c
>> index 1b599a623eea..482fdc9e25c2 100644
>> --- a/net/sunrpc/xprtrdma/verbs.c
>> +++ b/net/sunrpc/xprtrdma/verbs.c
>> @@ -1007,16 +1007,23 @@ struct rpcrdma_rep *rpcrdma_rep_create(struct
>> rpcrdma_xprt *r_xprt,
>>         return NULL;
>>  }
>>  
>> -/* No locking needed here. This function is invoked only by the
>> - * Receive completion handler, or during transport shutdown.
>> - */
>> -static void rpcrdma_rep_destroy(struct rpcrdma_rep *rep)
>> +static void rpcrdma_rep_destroy_locked(struct rpcrdma_rep *rep)
> 
> The name here is extremely confusing. As far as I can tell, this isn't
> called with any lock?

Fair enough.

I renamed it rpcrdma_rep_free() and it doesn't seem to have
any consequences for downstream commits in this series.

You could do a global edit, I can resend you this patch with
the change, or I can post a v4 of this series. Let me know
your preference.


>>  {
>> -       list_del(&rep->rr_all);
>>         rpcrdma_regbuf_free(rep->rr_rdmabuf);
>>         kfree(rep);
>>  }
>>  
>> +static void rpcrdma_rep_destroy(struct rpcrdma_rep *rep)
>> +{
>> +       struct rpcrdma_buffer *buf = &rep->rr_rxprt->rx_buf;
>> +
>> +       spin_lock(&buf->rb_lock);
>> +       list_del(&rep->rr_all);
>> +       spin_unlock(&buf->rb_lock);
>> +
>> +       rpcrdma_rep_destroy_locked(rep);
>> +}
>> +
>>  static struct rpcrdma_rep *rpcrdma_rep_get_locked(struct
>> rpcrdma_buffer *buf)
>>  {
>>         struct llist_node *node;
>> @@ -1049,8 +1056,18 @@ static void rpcrdma_reps_destroy(struct
>> rpcrdma_buffer *buf)
>>  {
>>         struct rpcrdma_rep *rep;
>>  
>> -       while ((rep = rpcrdma_rep_get_locked(buf)) != NULL)
>> -               rpcrdma_rep_destroy(rep);
>> +       spin_lock(&buf->rb_lock);
>> +       while ((rep = list_first_entry_or_null(&buf->rb_all_reps,
>> +                                              struct rpcrdma_rep,
>> +                                              rr_all)) != NULL) {
>> +               list_del(&rep->rr_all);
>> +               spin_unlock(&buf->rb_lock);
>> +
>> +               rpcrdma_rep_destroy_locked(rep);
>> +
>> +               spin_lock(&buf->rb_lock);
>> +       }
>> +       spin_unlock(&buf->rb_lock);
>>  }
>>  
>>  /**
>> 
>> 
> 
> -- 
> Trond Myklebust
> Linux NFS client maintainer, Hammerspace
> trond.myklebust@hammerspace.com

--
Chuck Lever




  reply index

Thread overview: 34+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-04-19 18:01 [PATCH v3 00/26] NFS/RDMA client patches for next Chuck Lever
2021-04-19 18:01 ` [PATCH v3 01/26] SUNRPC: Move fault injection call sites Chuck Lever
2021-04-19 18:05   ` Chuck Lever III
2021-04-19 18:01 ` [PATCH v3 02/26] SUNRPC: Remove trace_xprt_transmit_queued Chuck Lever
2021-04-19 18:01 ` [PATCH v3 03/26] SUNRPC: Add tracepoint that fires when an RPC is retransmitted Chuck Lever
2021-04-19 18:02 ` [PATCH v3 04/26] xprtrdma: Avoid Receive Queue wrapping Chuck Lever
2021-04-19 18:02 ` [PATCH v3 05/26] xprtrdma: Do not refresh Receive Queue while it is draining Chuck Lever
2021-04-19 18:02 ` [PATCH v3 06/26] xprtrdma: Put flushed Receives on free list instead of destroying them Chuck Lever
2021-04-19 18:02 ` [PATCH v3 07/26] xprtrdma: Improve locking around rpcrdma_rep destruction Chuck Lever
2021-04-23 21:06   ` Trond Myklebust
2021-04-24 17:39     ` Chuck Lever III [this message]
2021-04-24 17:59       ` Trond Myklebust
2021-04-19 18:02 ` [PATCH v3 08/26] xprtrdma: Improve commentary around rpcrdma_reps_unmap() Chuck Lever
2021-04-19 18:02 ` [PATCH v3 09/26] xprtrdma: Improve locking around rpcrdma_rep creation Chuck Lever
2021-04-19 18:02 ` [PATCH v3 10/26] xprtrdma: Fix cwnd update ordering Chuck Lever
2021-04-19 18:02 ` [PATCH v3 11/26] xprtrdma: Delete rpcrdma_recv_buffer_put() Chuck Lever
2021-04-19 18:02 ` [PATCH v3 12/26] xprtrdma: rpcrdma_mr_pop() already does list_del_init() Chuck Lever
2021-04-19 18:03 ` [PATCH v3 13/26] xprtrdma: Rename frwr_release_mr() Chuck Lever
2021-04-19 18:03 ` [PATCH v3 14/26] xprtrdma: Clarify use of barrier in frwr_wc_localinv_done() Chuck Lever
2021-04-19 18:03 ` [PATCH v3 15/26] xprtrdma: Do not recycle MR after FastReg/LocalInv flushes Chuck Lever
2021-04-25 14:19   ` Dan Aloni
2021-04-25 16:21     ` Chuck Lever III
2021-04-25 17:00       ` Dan Aloni
2021-04-19 18:03 ` [PATCH v3 16/26] xprtrdma: Do not wake RPC consumer on a failed LocalInv Chuck Lever
2021-04-19 18:03 ` [PATCH v3 17/26] xprtrdma: Avoid Send Queue wrapping Chuck Lever
2021-04-19 18:03 ` [PATCH v3 18/26] xprtrdma: Add tracepoints showing FastReg WRs and remote invalidation Chuck Lever
2021-04-19 18:03 ` [PATCH v3 19/26] xprtrdma: Add an rpcrdma_mr_completion_class Chuck Lever
2021-04-19 18:03 ` [PATCH v3 20/26] xprtrdma: Don't display r_xprt memory addresses in tracepoints Chuck Lever
2021-04-19 18:03 ` [PATCH v3 21/26] xprtrdma: Remove the RPC/RDMA QP event handler Chuck Lever
2021-04-19 18:03 ` [PATCH v3 22/26] xprtrdma: Move fr_cid to struct rpcrdma_mr Chuck Lever
2021-04-19 18:04 ` [PATCH v3 23/26] xprtrdma: Move cqe " Chuck Lever
2021-04-19 18:04 ` [PATCH v3 24/26] xprtrdma: Move fr_linv_done field " Chuck Lever
2021-04-19 18:04 ` [PATCH v3 25/26] xprtrdma: Move the Work Request union " Chuck Lever
2021-04-19 18:04 ` [PATCH v3 26/26] xprtrdma: Move fr_mr field " Chuck Lever

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