[PATCH] hugetlbfs: move resv_map to hugetlbfs_inode_info

[Yufen Yu <yuyufen@huawei.com>]

Commit 58b6e5e8f1ad ("hugetlbfs: fix memory leak for resv_map")
fix memory leak for resv_map. It only allocate resv_map for inode mode
is 'S_ISREG' and 'S_ISLNK', avoiding i_mapping->private_data be set as
bdev_inode private_data.

However, for inode mode that is 'S_ISBLK', hugetlbfs_evict_inode() may
free or modify i_mapping->private_data that is owned by bdev inode,
which is not expected!

Fortunately, bdev filesystem have not actually use i_mapping->private_data.
Thus, this bug has not caused serious impact. But, we can not ensure
bdev will not use that field in the furture. And hugetlbfs should not
depend on bdev filesystem implementation.

We fix the problem by moving resv_map to hugetlbfs_inode_info. It may
be more reasonable.

Fixes: 58b6e5e8f1ad ("hugetlbfs: fix memory leak for resv_map")
Cc: Michal Hocko <mhocko@kernel.org>
Cc: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Cc: Naoya Horiguchi <n-horiguchi@ah.jp.nec.com>
Signed-off-by: Yufen Yu <yuyufen@huawei.com>
---
 fs/hugetlbfs/inode.c    | 11 ++++++++---
 include/linux/hugetlb.h |  1 +
 mm/hugetlb.c            |  2 +-
 3 files changed, 10 insertions(+), 4 deletions(-)

diff --git a/fs/hugetlbfs/inode.c b/fs/hugetlbfs/inode.c
index 9285dd4f4b1c..f1342a3fa716 100644
--- a/fs/hugetlbfs/inode.c
+++ b/fs/hugetlbfs/inode.c
@@ -497,12 +497,15 @@ static void remove_inode_hugepages(struct inode *inode, loff_t lstart,
 static void hugetlbfs_evict_inode(struct inode *inode)
 {
 	struct resv_map *resv_map;
+	struct hugetlbfs_inode_info *info = HUGETLBFS_I(inode);
 
 	remove_inode_hugepages(inode, 0, LLONG_MAX);
-	resv_map = (struct resv_map *)inode->i_mapping->private_data;
+	resv_map = info->resv_map;
 	/* root inode doesn't have the resv_map, so we should check it */
-	if (resv_map)
+	if (resv_map) {
 		resv_map_release(&resv_map->refs);
+		info->resv_map = NULL;
+	}
 	clear_inode(inode);
 }
 
@@ -777,7 +780,7 @@ static struct inode *hugetlbfs_get_inode(struct super_block *sb,
 				&hugetlbfs_i_mmap_rwsem_key);
 		inode->i_mapping->a_ops = &hugetlbfs_aops;
 		inode->i_atime = inode->i_mtime = inode->i_ctime = current_time(inode);
-		inode->i_mapping->private_data = resv_map;
+		info->resv_map = resv_map;
 		info->seals = F_SEAL_SEAL;
 		switch (mode & S_IFMT) {
 		default:
@@ -1047,6 +1050,7 @@ static struct inode *hugetlbfs_alloc_inode(struct super_block *sb)
 	 * private inode.  This simplifies hugetlbfs_destroy_inode.
 	 */
 	mpol_shared_policy_init(&p->policy, NULL);
+	p->resv_map = NULL;
 
 	return &p->vfs_inode;
 }
@@ -1061,6 +1065,7 @@ static void hugetlbfs_destroy_inode(struct inode *inode)
 {
 	hugetlbfs_inc_free_inodes(HUGETLBFS_SB(inode->i_sb));
 	mpol_free_shared_policy(&HUGETLBFS_I(inode)->policy);
+	HUGETLBFS_I(inode)->resv_map = NULL;
 	call_rcu(&inode->i_rcu, hugetlbfs_i_callback);
 }
 
diff --git a/include/linux/hugetlb.h b/include/linux/hugetlb.h
index 11943b60f208..584030631045 100644
--- a/include/linux/hugetlb.h
+++ b/include/linux/hugetlb.h
@@ -297,6 +297,7 @@ struct hugetlbfs_inode_info {
 	struct shared_policy policy;
 	struct inode vfs_inode;
 	unsigned int seals;
+	struct resv_map *resv_map;
 };
 
 static inline struct hugetlbfs_inode_info *HUGETLBFS_I(struct inode *inode)
diff --git a/mm/hugetlb.c b/mm/hugetlb.c
index fe74f94e5327..a2648edffb02 100644
--- a/mm/hugetlb.c
+++ b/mm/hugetlb.c
@@ -740,7 +740,7 @@ void resv_map_release(struct kref *ref)
 
 static inline struct resv_map *inode_resv_map(struct inode *inode)
 {
-	return inode->i_mapping->private_data;
+	return HUGETLBFS_I(inode)->resv_map;
 }
 
 static struct resv_map *vma_resv_map(struct vm_area_struct *vma)
-- 
2.16.2.dirty