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Date:   Mon, 21 Jan 2019 11:12:02 -0800
From:   Davidlohr Bueso <dave@stgolabs.net>
To:     Jason Gunthorpe <jgg@mellanox.com>
Cc:     "akpm@linux-foundation.org" <akpm@linux-foundation.org>,
        "dledford@redhat.com" <dledford@redhat.com>,
        "jack@suse.de" <jack@suse.de>,
        "ira.weiny@intel.com" <ira.weiny@intel.com>,
        "linux-rdma@vger.kernel.org" <linux-rdma@vger.kernel.org>,
        "linux-mm@kvack.org" <linux-mm@kvack.org>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
        Davidlohr Bueso <dbueso@suse.de>, willy@infradead.org
Subject: Re: [PATCH 6/6] drivers/IB,core: reduce scope of mmap_sem
Message-ID: <20190121191202.xygjopuuifyepd63@linux-r8p5>
Mail-Followup-To: Jason Gunthorpe <jgg@mellanox.com>,
        "akpm@linux-foundation.org" <akpm@linux-foundation.org>,
        "dledford@redhat.com" <dledford@redhat.com>,
        "jack@suse.de" <jack@suse.de>,
        "ira.weiny@intel.com" <ira.weiny@intel.com>,
        "linux-rdma@vger.kernel.org" <linux-rdma@vger.kernel.org>,
        "linux-mm@kvack.org" <linux-mm@kvack.org>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
        Davidlohr Bueso <dbueso@suse.de>, willy@infradead.org
References: <20190121174220.10583-1-dave@stgolabs.net>
 <20190121174220.10583-7-dave@stgolabs.net>
 <20190121183218.GK25149@mellanox.com>
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On Mon, 21 Jan 2019, Jason Gunthorpe wrote:

>On Mon, Jan 21, 2019 at 09:42:20AM -0800, Davidlohr Bueso wrote:
>> ib_umem_get() uses gup_longterm() and relies on the lock to
>> stabilze the vma_list, so we cannot really get rid of mmap_sem
>> altogether, but now that the counter is atomic, we can get of
>> some complexity that mmap_sem brings with only pinned_vm.
>>
>> Reviewed-by: Ira Weiny <ira.weiny@intel.com>
>> Signed-off-by: Davidlohr Bueso <dbueso@suse.de>
>> ---
>>  drivers/infiniband/core/umem.c | 41 ++---------------------------------------
>>  1 file changed, 2 insertions(+), 39 deletions(-)
>
>I think this addresses my comment..
>
>Considering that it is almost all infiniband, I'd rather it go it go
>through the RDMA tree with an ack from mm people? Please advise..

Yeah also Cc'ing Willy who I forgot to add for v2.

>
>Thanks,
>Jason