linux-kernel - Re: [PATCH 3/3] net/xdp: convert put_page() to put_user

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Message-ID: <20190723124707.GB15357@ziepe.ca>
Date:   Tue, 23 Jul 2019 09:47:07 -0300
From:   Jason Gunthorpe <jgg@...pe.ca>
To:     John Hubbard <jhubbard@...dia.com>
Cc:     Ira Weiny <ira.weiny@...el.com>, john.hubbard@...il.com,
        Andrew Morton <akpm@...ux-foundation.org>,
        Alexander Viro <viro@...iv.linux.org.uk>,
        Björn Töpel <bjorn.topel@...el.com>,
        Boaz Harrosh <boaz@...xistor.com>,
        Christoph Hellwig <hch@....de>,
        Daniel Vetter <daniel@...ll.ch>,
        Dan Williams <dan.j.williams@...el.com>,
        Dave Chinner <david@...morbit.com>,
        David Airlie <airlied@...ux.ie>,
        "David S . Miller" <davem@...emloft.net>,
        Ilya Dryomov <idryomov@...il.com>, Jan Kara <jack@...e.cz>,
        Jens Axboe <axboe@...nel.dk>,
        Jérôme Glisse <jglisse@...hat.com>,
        Johannes Thumshirn <jthumshirn@...e.de>,
        Magnus Karlsson <magnus.karlsson@...el.com>,
        Matthew Wilcox <willy@...radead.org>,
        Miklos Szeredi <miklos@...redi.hu>,
        Ming Lei <ming.lei@...hat.com>, Sage Weil <sage@...hat.com>,
        Santosh Shilimkar <santosh.shilimkar@...cle.com>,
        Yan Zheng <zyan@...hat.com>, netdev@...r.kernel.org,
        dri-devel@...ts.freedesktop.org, linux-mm@...ck.org,
        linux-rdma@...r.kernel.org, bpf@...r.kernel.org,
        LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 3/3] net/xdp: convert put_page() to put_user_page*()

On Mon, Jul 22, 2019 at 09:41:34PM -0700, John Hubbard wrote:

> * The leading underscores are often used for the more elaborate form of the
> call (as oppposed to decorating the core function name with "_flags", for
> example).

IMHO usually the __ version of a public symbol means something like
'why are you using this? you probably should not'

Often because the __ version has no locking or some other dangerous
configuration like that.

Jason