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From: Jason Gunthorpe <jgg@nvidia.com>
To: Gal Pressman <galpress@amazon.com>
Cc: Doug Ledford <dledford@redhat.com>,
	linux-rdma@vger.kernel.org,
	Alexander Matushevsky <matua@amazon.com>,
	Yossi Leybovich <sleybo@amazon.com>,
	Leon Romanovsky <leonro@nvidia.com>, Peter Xu <peterx@redhat.com>,
	Andrew Morton <akpm@linux-foundation.org>,
	Mike Kravetz <mike.kravetz@oracle.com>
Subject: Re: [PATCH for-next v4] RDMA/nldev: Add copy-on-fork attribute to get sys command
Date: Tue, 27 Apr 2021 15:37:10 -0300
Message-ID: <20210427183710.GA3259427@nvidia.com> (raw)
In-Reply-To: <20210418121025.66849-1-galpress@amazon.com>

On Sun, Apr 18, 2021 at 03:10:25PM +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.
> 
> Don't backport this patch unless you also have the following series:
> 70e806e4e645 ("mm: Do early cow for pinned pages during fork() for ptes")
> and 4eae4efa2c29 ("hugetlb: do early cow when page pinned on src mm").
> 
> Fixes: 70e806e4e645 ("mm: Do early cow for pinned pages during fork() for ptes")
> Fixes: 4eae4efa2c29 ("hugetlb: do early cow when page pinned on src mm")
> Signed-off-by: Gal Pressman <galpress@amazon.com>
> Reviewed-by: Leon Romanovsky <leonro@nvidia.com>
> ---
> PR was sent:
> https://github.com/linux-rdma/rdma-core/pull/975
> 
> Changelog -
> v3->v4: https://lore.kernel.org/linux-rdma/20210412064150.40064-1-galpress@amazon.com/
> * Mention that nla_put_u8() return value is ignored on purpose
> 
> v2->v3: https://lore.kernel.org/linux-rdma/21317d2c-9a8e-0dd7-3678-d2933c5053c4@amazon.com/
> * Remove check if copy-on-fork attribute was provided from nldev_set_sys_set_doit()
> 
> v1->v2: https://lore.kernel.org/linux-rdma/20210405114722.98904-1-galpress@amazon.com/
> * Remove nla_put_u8() return value check
> * Add commit hashes to commit message and code comment
> ---
>  drivers/infiniband/core/nldev.c  | 14 ++++++++++++++
>  include/uapi/rdma/rdma_netlink.h |  2 ++
>  2 files changed, 16 insertions(+)

Applied to for-next, not the enum number will have changed compared to
what you sent

Thanks,
Jason

      reply index

Thread overview: 2+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-04-18 12:10 Gal Pressman
2021-04-27 18:37 ` Jason Gunthorpe [this message]

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