Re: [next] x86: fs/hugetlbfs/inode.c:673:16: error: variable 'm_index' is uninitialized when used here [-Werror,-Wuninitialized]

From: Mike Kravetz <mike.kravetz@oracle.com>
To: Naresh Kamboju <naresh.kamboju@linaro.org>,
	Andrew Morton <akpm@linux-foundation.org>
Cc: linux-mm <linux-mm@kvack.org>,
	open list <linux-kernel@vger.kernel.org>,
	regressions@lists.linux.dev,
	Nathan Chancellor <nathan@kernel.org>,
	clang-built-linux <clang-built-linux@googlegroups.com>,
	Muchun Song <songmuchun@bytedance.com>,
	Andrea Arcangeli <aarcange@redhat.com>,
	"Aneesh Kumar K.V" <aneesh.kumar@linux.vnet.ibm.com>,
	Axel Rasmussen <axelrasmussen@google.com>,
	David Hildenbrand <david@redhat.com>,
	Davidlohr Bueso <dave@stgolabs.net>,
	James Houghton <jthoughton@google.com>,
	"Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>,
	Miaohe Lin <linmiaohe@huawei.com>, Michal Hocko <mhocko@suse.com>,
	Mina Almasry <almasrymina@google.com>,
	Naoya Horiguchi <naoya.horiguchi@linux.dev>,
	Pasha Tatashin <pasha.tatashin@soleen.com>,
	Peter Xu <peterx@redhat.com>,
	Prakash Sangappa <prakash.sangappa@oracle.com>
Subject: Re: [next] x86: fs/hugetlbfs/inode.c:673:16: error: variable 'm_index' is uninitialized when used here [-Werror,-Wuninitialized]
Date: Thu, 25 Aug 2022 09:56:15 -0700	[thread overview]
Message-ID: <Ywepr7C2X20ZvLdn@monkey> (raw)
In-Reply-To: <CA+G9fYsHVdu0toduQqk6vsR8Z8mOVzZ9-_p3O5fjQ5mOpSxsDA@mail.gmail.com>

On 08/25/22 16:13, Naresh Kamboju wrote:
> The x86_64 and i386 clang builds failed due to these warnings / errors
> on Linux next-20220825.
> 
> Reported-by: Linux Kernel Functional Testing <lkft@linaro.org>
> 
> fs/hugetlbfs/inode.c:673:16: error: variable 'm_index' is
> uninitialized when used here [-Werror,-Wuninitialized]
>                                                 m_start, m_index, truncate_op);
>                                                          ^~~~~~~
> fs/hugetlbfs/inode.c:651:26: note: initialize the variable 'm_index'

Thanks!  That really should be 'index' and not 'm_index'.  The variable
m_index was used in a previous version of the code and should have been
deleted.  Depending on the uninitialized value of m_index, this could
cause long delays as the called routine checks the range m_start to m_index.

Andrew, how would you like to address in your tree?  The following patch
can be applied on top of the original (next commit fcc0d3d00d74 "hugetlb:
handle truncate racing with page faults").  Or, I could squash and
resend the original, or resend the entire series.


From 99aae359c3a744e6718045d2f24b55c84bed4d56 Mon Sep 17 00:00:00 2001
From: Mike Kravetz <mike.kravetz@oracle.com>
Date: Thu, 25 Aug 2022 09:49:08 -0700
Subject: [PATCH] hugetlb: fix/remove uninitialized variable in
 remove_inode_hugepages

Code introduced for the routine remove_inode_hugepages by patch "hugetlb:
handle truncate racing with page faults", incorrectly uses a variable
m_index.  This is a remnant from a previous version of the code when
under development.  Use the correct variable 'index' and remove
'm_index' from the routine.

Signed-off-by: Mike Kravetz <mike.kravetz@oracle.com>
---
 fs/hugetlbfs/inode.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/fs/hugetlbfs/inode.c b/fs/hugetlbfs/inode.c
index 52d9b390389b..2f1d6da1bafb 100644
--- a/fs/hugetlbfs/inode.c
+++ b/fs/hugetlbfs/inode.c
@@ -648,7 +648,7 @@ static void remove_inode_hugepages(struct inode *inode, loff_t lstart,
 	const pgoff_t start = lstart >> huge_page_shift(h);
 	const pgoff_t end = lend >> huge_page_shift(h);
 	pgoff_t m_end = lm_end >> huge_page_shift(h);
-	pgoff_t m_start, m_index;
+	pgoff_t m_start;
 	struct folio_batch fbatch;
 	struct folio *folio;
 	pgoff_t next, index;
@@ -670,7 +670,7 @@ static void remove_inode_hugepages(struct inode *inode, loff_t lstart,
 			 * due to a race with fault code.
 			 */
 			freed += fault_lock_inode_indicies(h, inode, mapping,
-						m_start, m_index, truncate_op);
+						m_start, index, truncate_op);
 
 			/*
 			 * Remove folio that was part of folio_batch.
-- 
2.37.1


