linux-kernel - Re: [PATCH 31/34] nfs: convert put_page() to put_user

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Date:   Sat, 3 Aug 2019 02:27:55 +0100
From:   Calum Mackay <calum.mackay@...cle.com>
To:     john.hubbard@...il.com, Andrew Morton <akpm@...ux-foundation.org>
Cc:     calum.mackay@...cle.com, Christoph Hellwig <hch@...radead.org>,
        Dan Williams <dan.j.williams@...el.com>,
        Dave Chinner <david@...morbit.com>,
        Dave Hansen <dave.hansen@...ux.intel.com>,
        Ira Weiny <ira.weiny@...el.com>, Jan Kara <jack@...e.cz>,
        Jason Gunthorpe <jgg@...pe.ca>,
        Jérôme Glisse <jglisse@...hat.com>,
        LKML <linux-kernel@...r.kernel.org>,
        amd-gfx@...ts.freedesktop.org, ceph-devel@...r.kernel.org,
        devel@...verdev.osuosl.org, devel@...ts.orangefs.org,
        dri-devel@...ts.freedesktop.org, intel-gfx@...ts.freedesktop.org,
        kvm@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
        linux-block@...r.kernel.org, linux-crypto@...r.kernel.org,
        linux-fbdev@...r.kernel.org, linux-fsdevel@...r.kernel.org,
        linux-media@...r.kernel.org, linux-mm@...ck.org,
        linux-nfs@...r.kernel.org, linux-rdma@...r.kernel.org,
        linux-rpi-kernel@...ts.infradead.org, linux-xfs@...r.kernel.org,
        netdev@...r.kernel.org, rds-devel@....oracle.com,
        sparclinux@...r.kernel.org, x86@...nel.org,
        xen-devel@...ts.xenproject.org, John Hubbard <jhubbard@...dia.com>,
        Trond Myklebust <trond.myklebust@...merspace.com>,
        Anna Schumaker <anna.schumaker@...app.com>
Subject: Re: [PATCH 31/34] nfs: convert put_page() to put_user_page*()

On 02/08/2019 3:20 am, john.hubbard@...il.com wrote:
> From: John Hubbard <jhubbard@...dia.com>
> 
> For pages that were retained via get_user_pages*(), release those pages
> via the new put_user_page*() routines, instead of via put_page() or
> release_pages().
> 
> This is part a tree-wide conversion, as described in commit fc1d8e7cca2d
> ("mm: introduce put_user_page*(), placeholder versions").
> 
> Cc: Trond Myklebust <trond.myklebust@...merspace.com>
> Cc: Anna Schumaker <anna.schumaker@...app.com>
> Cc: linux-nfs@...r.kernel.org
> Signed-off-by: John Hubbard <jhubbard@...dia.com>
> ---
>   fs/nfs/direct.c | 4 +---
>   1 file changed, 1 insertion(+), 3 deletions(-)
> 
> diff --git a/fs/nfs/direct.c b/fs/nfs/direct.c
> index 0cb442406168..b00b89dda3c5 100644
> --- a/fs/nfs/direct.c
> +++ b/fs/nfs/direct.c
> @@ -278,9 +278,7 @@ ssize_t nfs_direct_IO(struct kiocb *iocb, struct iov_iter *iter)
>   
>   static void nfs_direct_release_pages(struct page **pages, unsigned int npages)
>   {
> -	unsigned int i;
> -	for (i = 0; i < npages; i++)
> -		put_page(pages[i]);
> +	put_user_pages(pages, npages);
>   }

Since it's static, and only called twice, might it be better to change 
its two callers [nfs_direct_{read,write}_schedule_iovec()] to call 
put_user_pages() directly, and remove nfs_direct_release_pages() entirely?

thanks,
calum.


>   
>   void nfs_init_cinfo_from_dreq(struct nfs_commit_info *cinfo,
>