linux-kernel - Re: [PATCH] mm/gup: Use put_user_page*() instead of put

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Date:   Mon, 15 Jul 2019 12:29:17 +0530
From:   Bharath Vedartham <linux.bhar@...il.com>
To:     Jens Axboe <axboe@...nel.dk>
Cc:     akpm@...ux-foundation.org, ira.weiny@...el.com,
        jhubbard@...dia.com, Mauro Carvalho Chehab <mchehab@...nel.org>,
        Dimitri Sivanich <sivanich@....com>,
        Arnd Bergmann <arnd@...db.de>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Alex Williamson <alex.williamson@...hat.com>,
        Cornelia Huck <cohuck@...hat.com>,
        Alexander Viro <viro@...iv.linux.org.uk>,
        Björn Töpel <bjorn.topel@...el.com>,
        Magnus Karlsson <magnus.karlsson@...el.com>,
        "David S. Miller" <davem@...emloft.net>,
        Alexei Starovoitov <ast@...nel.org>,
        Daniel Borkmann <daniel@...earbox.net>,
        Jakub Kicinski <jakub.kicinski@...ronome.com>,
        Jesper Dangaard Brouer <hawk@...nel.org>,
        John Fastabend <john.fastabend@...il.com>,
        Enrico Weigelt <info@...ux.net>,
        Thomas Gleixner <tglx@...utronix.de>,
        Alexios Zavras <alexios.zavras@...el.com>,
        Dan Carpenter <dan.carpenter@...cle.com>,
        Max Filippov <jcmvbkbc@...il.com>,
        Matt Sickler <Matt.Sickler@...tronics.com>,
        "Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>,
        Keith Busch <keith.busch@...el.com>,
        YueHaibing <yuehaibing@...wei.com>, linux-media@...r.kernel.org,
        linux-kernel@...r.kernel.org, devel@...verdev.osuosl.org,
        kvm@...r.kernel.org, linux-block@...r.kernel.org,
        linux-fsdevel@...r.kernel.org, linux-mm@...ck.org,
        netdev@...r.kernel.org, bpf@...r.kernel.org,
        xdp-newbies@...r.kernel.org
Subject: Re: [PATCH] mm/gup: Use put_user_page*() instead of put_page*()

On Sun, Jul 14, 2019 at 08:33:57PM -0600, Jens Axboe wrote:
> On 7/14/19 1:08 PM, Bharath Vedartham wrote:
> > diff --git a/fs/io_uring.c b/fs/io_uring.c
> > index 4ef62a4..b4a4549 100644
> > --- a/fs/io_uring.c
> > +++ b/fs/io_uring.c
> > @@ -2694,10 +2694,9 @@ static int io_sqe_buffer_register(struct io_ring_ctx *ctx, void __user *arg,
> >   			 * if we did partial map, or found file backed vmas,
> >   			 * release any pages we did get
> >   			 */
> > -			if (pret > 0) {
> > -				for (j = 0; j < pret; j++)
> > -					put_page(pages[j]);
> > -			}
> > +			if (pret > 0)
> > +				put_user_pages(pages, pret);
> > +
> >   			if (ctx->account_mem)
> >   				io_unaccount_mem(ctx->user, nr_pages);
> >   			kvfree(imu->bvec);
> 
> You handled just the failure case of the buffer registration, but not
> the actual free in io_sqe_buffer_unregister().
> 
> -- 
> Jens Axboe
Yup got it! Thanks! I won't be sending a patch again as fs/io_uring.c
may have larger local changes for put_user_pages.

Thanks