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Date:   Sun, 25 Apr 2021 17:19:14 +0300
From:   Dan Aloni <dan@kernelim.com>
To:     Chuck Lever <chuck.lever@oracle.com>
Cc:     trondmy@hammerspace.com, linux-nfs@vger.kernel.org,
        linux-rdma@vger.kernel.org
Subject: Re: [PATCH v3 15/26] xprtrdma: Do not recycle MR after
 FastReg/LocalInv flushes
Message-ID: <20210425141914.6govk2lm2hfosdie@gmail.com>
References: <161885481568.38598.16682844600209775665.stgit@manet.1015granger.net>
 <161885539285.38598.13978652738422395833.stgit@manet.1015granger.net>
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On Mon, Apr 19, 2021 at 02:03:12PM -0400, Chuck Lever wrote:
> Better not to touch MRs involved in a flush or post error until the
> Send and Receive Queues are drained and the transport is fully
> quiescent. Simply don't insert such MRs back onto the free list.
> They remain on mr_all and will be released when the connection is
> torn down.
> 
> I had thought that recycling would prevent hardware resources from
> being tied up for a long time. However, since v5.7, a transport
> disconnect destroys the QP and other hardware-owned resources. The
> MRs get cleaned up nicely at that point.
> 
> Signed-off-by: Chuck Lever <chuck.lever@oracle.com>

Is this a fix for the crash below?  I just wonder if it appeared for
others in the wild, and the fix is not just theoretical.

    WARNING: CPU: 5 PID: 20312 at lib/list_debug.c:53 __list_del_entry+0x63/0xd0
    list_del corruption, ffff9df150b06768->next is LIST_POISON1 (dead000000000100)

    Call Trace:
     [<ffffffff99764147>] dump_stack+0x19/0x1b
     [<ffffffff99098848>] __warn+0xd8/0x100
     [<ffffffff990988cf>] warn_slowpath_fmt+0x5f/0x80
     [<ffffffff9921d5f6>] ? kfree+0x106/0x140
     [<ffffffff99396953>] __list_del_entry+0x63/0xd0
     [<ffffffff993969cd>] list_del+0xd/0x30
     [<ffffffffc0bb307f>] frwr_mr_recycle+0xaf/0x150 [rpcrdma]
     [<ffffffffc0bb3264>] frwr_wc_localinv+0x94/0xa0 [rpcrdma]
     [<ffffffffc067d20e>] __ib_process_cq+0x8e/0x100 [ib_core]
     [<ffffffffc067d2f9>] ib_cq_poll_work+0x29/0x70 [ib_core]
     [<ffffffff990baf9f>] process_one_work+0x17f/0x440
     [<ffffffff990bc036>] worker_thread+0x126/0x3c0
     [<ffffffff990bbf10>] ? manage_workers.isra.25+0x2a0/0x2a0
     [<ffffffff990c2e81>] kthread+0xd1/0xe0
     [<ffffffff990c2db0>] ? insert_kthread_work+0x40/0x40
     [<ffffffff99776c37>] ret_from_fork_nospec_begin+0x21/0x21
     [<ffffffff990c2db0>] ? insert_kthread_work+0x40/0x40

-- 
Dan Aloni