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Date:   Mon, 5 Apr 2021 14:58:37 +0300
From:   Leon Romanovsky <leon@kernel.org>
To:     Gal Pressman <galpress@amazon.com>
Cc:     Jason Gunthorpe <jgg@nvidia.com>,
        Doug Ledford <dledford@redhat.com>, linux-rdma@vger.kernel.org,
        Alexander Matushevsky <matua@amazon.com>,
        Yossi Leybovich <sleybo@amazon.com>,
        Jason Gunthorpe <jgg@ziepe.ca>
Subject: Re: [PATCH for-next] RDMA/nldev: Add copy-on-fork attribute to get
 sys command
Message-ID: <YGr7bY9CcQoDXSb2@unreal>
References: <20210405114722.98904-1-galpress@amazon.com>
 <YGr7EajqXvSGyZfy@unreal>
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On Mon, Apr 05, 2021 at 02:57:05PM +0300, Leon Romanovsky wrote:
> On Mon, Apr 05, 2021 at 02:47:21PM +0300, Gal Pressman wrote:
> > The new attribute indicates that the kernel copies DMA pages on fork,
> > hence libibverbs' fork support through madvise and MADV_DONTFORK is not
> > needed.
> > 
> > The introduced attribute is always reported as supported since the
> > kernel has the patch that added the copy-on-fork behavior. This allows
> > the userspace library to identify older vs newer kernel versions.
> > Extra care should be taken when backporting this patch as it relies on
> > the fact that the copy-on-fork patch is merged, hence no check for
> > support is added.
> 
> Please be more specific, add SHA-1 of that patch and wrote the same
> comment near "err = nla_put_u8(msg, RDMA_NLDEV_SYS_ATTR_COPY_ON_FORK,
> 1);" line.

And rdmatool should be updated too.

Thanks