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Date:   Thu, 20 Aug 2020 13:55:15 -0700
From:   Andrew Morton <akpm@linux-foundation.org>
To:     Naresh Kamboju <naresh.kamboju@linaro.org>
Cc:     Linux-Next Mailing List <linux-next@vger.kernel.org>,
        open list <linux-kernel@vger.kernel.org>,
        linux-mm <linux-mm@kvack.org>, lkft-triage@lists.linaro.org,
        linuxarm@huawei.com, Barry Song <song.bao.hua@hisilicon.com>,
        John Hubbard <jhubbard@nvidia.com>, Jan Kara <jack@suse.cz>,
        =?UTF-8?B?SsOpcsO0bWU=?= Glisse <jglisse@redhat.com>,
        "Matthew Wilcox (Oracle)" <willy@infradead.org>,
        Al Viro <viro@zeniv.linux.org.uk>,
        Christoph Hellwig <hch@infradead.org>,
        Dan Williams <dan.j.williams@intel.com>,
        Dave Chinner <david@fromorbit.com>,
        Jason Gunthorpe <jgg@ziepe.ca>,
        Jonathan Corbet <corbet@lwn.net>,
        Michal Hocko <mhocko@suse.com>,
        Mike Kravetz <mike.kravetz@oracle.com>,
        Shuah Khan <shuah@kernel.org>, Vlastimil Babka <vbabka@suse.cz>
Subject: Re: mm/gup.c:1922:7: error: implicit declaration of function
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On Thu, 20 Aug 2020 14:59:52 +0530 Naresh Kamboju <naresh.kamboju@linaro.org> wrote:

> arm and riscv architecture build failed on linux next 20200820 tag.
> 
> make -sk KBUILD_BUILD_USER=TuxBuild -C/linux -j16 ARCH=arm
> CROSS_COMPILE=arm-linux-gnueabihf- HOSTCC=gcc CC="sccache
> arm-linux-gnueabihf-gcc" O=build zImage
> 
> 348#
> 349../mm/gup.c: In function ‘get_user_pages’:
> 350../mm/gup.c:1922:7: error: implicit declaration of function
> ‘is_valid_gup_flags’ [-Werror=implicit-function-declaration]
> 351 1922 | if (!is_valid_gup_flags(gup_flags))
> 352 | ^~~~~~~~~~~~~~~~~~
> 353cc1: some warnings being treated as errors
> 

Yes, thanks.

From: Andrew Morton <akpm@linux-foundation.org>
Subject: mm-gup-dont-permit-users-to-call-get_user_pages-with-foll_longterm-fix

fix CONFIG_MMU=n build

Link: https://lkml.kernel.org/r/CA+G9fYuNS3k0DVT62twfV746pfNhCSrk5sVMcOcQ1PGGnEseyw@mail.gmail.com
Reported-by: Naresh Kamboju <naresh.kamboju@linaro.org>
Cc: Barry Song <song.bao.hua@hisilicon.com>
Cc: Stephen Rothwell <sfr@canb.auug.org.au>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---

 mm/gup.c |   38 +++++++++++++++++++-------------------
 1 file changed, 19 insertions(+), 19 deletions(-)

--- a/mm/gup.c~mm-gup-dont-permit-users-to-call-get_user_pages-with-foll_longterm-fix
+++ a/mm/gup.c
@@ -1759,6 +1759,25 @@ static __always_inline long __gup_longte
 }
 #endif /* CONFIG_FS_DAX || CONFIG_CMA */
 
+static bool is_valid_gup_flags(unsigned int gup_flags)
+{
+	/*
+	 * FOLL_PIN must only be set internally by the pin_user_pages*() APIs,
+	 * never directly by the caller, so enforce that with an assertion:
+	 */
+	if (WARN_ON_ONCE(gup_flags & FOLL_PIN))
+		return false;
+	/*
+	 * FOLL_PIN is a prerequisite to FOLL_LONGTERM. Another way of saying
+	 * that is, FOLL_LONGTERM is a specific case, more restrictive case of
+	 * FOLL_PIN.
+	 */
+	if (WARN_ON_ONCE(gup_flags & FOLL_LONGTERM))
+		return false;
+
+	return true;
+}
+
 #ifdef CONFIG_MMU
 static long __get_user_pages_remote(struct mm_struct *mm,
 				    unsigned long start, unsigned long nr_pages,
@@ -1789,25 +1808,6 @@ static long __get_user_pages_remote(stru
 				       gup_flags | FOLL_TOUCH | FOLL_REMOTE);
 }
 
-static bool is_valid_gup_flags(unsigned int gup_flags)
-{
-	/*
-	 * FOLL_PIN must only be set internally by the pin_user_pages*() APIs,
-	 * never directly by the caller, so enforce that with an assertion:
-	 */
-	if (WARN_ON_ONCE(gup_flags & FOLL_PIN))
-		return false;
-	/*
-	 * FOLL_PIN is a prerequisite to FOLL_LONGTERM. Another way of saying
-	 * that is, FOLL_LONGTERM is a specific case, more restrictive case of
-	 * FOLL_PIN.
-	 */
-	if (WARN_ON_ONCE(gup_flags & FOLL_LONGTERM))
-		return false;
-
-	return true;
-}
-
 /**
  * get_user_pages_remote() - pin user pages in memory
  * @mm:		mm_struct of target mm
_