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From: Trond Myklebust <trondmy@hammerspace.com>
To: "chuck.lever@oracle.com" <chuck.lever@oracle.com>
Cc: "linux-nfs@vger.kernel.org" <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 17:59:25 +0000
Message-ID: <4975b75027b5407c5fef961f9be123b781b40559.camel@hammerspace.com> (raw)
In-Reply-To: <0DA1937B-3EA1-45A9-BD37-F7426764F83D@oracle.com>

On Sat, 2021-04-24 at 17:39 +0000, Chuck Lever III wrote:
> 
> 
> > 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.

Sounds good.

> 
> 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.
> 

Can you please just resend this patch with the update, unless there are
repercussions for the other patches? (in which case a v4 would be
welcome)

> 
> > >  {
> > > -       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
> 
> 
> 

-- 
Trond Myklebust
Linux NFS client maintainer, Hammerspace
trond.myklebust@hammerspace.com



  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
2021-04-24 17:59       ` Trond Myklebust [this message]
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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