linux-kernel - [PATCH] mm/hugetlb: i_mmap_lock_write before unmapping in remove_inode

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Date:	Wed, 21 Oct 2015 18:42:27 -0700
From:	Mike Kravetz <mike.kravetz@...cle.com>
To:	linux-mm@...ck.org, linux-kernel@...r.kernel.org
Cc:	Dave Hansen <dave.hansen@...ux.intel.com>,
	Naoya Horiguchi <n-horiguchi@...jp.nec.com>,
	Hugh Dickins <hughd@...gle.com>,
	Davidlohr Bueso <dave@...olabs.net>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Mike Kravetz <mike.kravetz@...cle.com>
Subject: [PATCH] mm/hugetlb: i_mmap_lock_write before unmapping in remove_inode_hugepages

Code was added to remove_inode_hugepages that will unmap a page if
it is mapped.  i_mmap_lock_write() must be taken during the call
to hugetlb_vmdelete_list().  This is to prevent mappings(vmas) from
being added or deleted while the list of vmas is being examined.

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

diff --git a/fs/hugetlbfs/inode.c b/fs/hugetlbfs/inode.c
index f25b72f..0f3999d 100644
--- a/fs/hugetlbfs/inode.c
+++ b/fs/hugetlbfs/inode.c
@@ -428,9 +428,11 @@ static void remove_inode_hugepages(struct inode *inode, loff_t lstart,
 			 * until we finish removing the page.
 			 */
 			if (page_mapped(page)) {
+				i_mmap_lock_write(mapping);
 				hugetlb_vmdelete_list(&mapping->i_mmap,
 					next * pages_per_huge_page(h),
 					(next + 1) * pages_per_huge_page(h));
+				i_mmap_unlock_write(mapping);
 			}
 
 			lock_page(page);
-- 
2.4.3

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