hugetlb: fix lockdep splat caused by pmd sharing

[~andy/linux] / fs / hugetlbfs / inode.c

diff --git a/fs/hugetlbfs/inode.c b/fs/hugetlbfs/inode.c
index a3f868ae3fd48f043f91a059ede274b20b431c3b..34423978b17083d73b038d360d72b47dc08c6693 100644 (file)
--- a/fs/hugetlbfs/inode.c
+++ b/fs/hugetlbfs/inode.c
@@ -463,6 +463,14 @@ static struct inode *hugetlbfs_get_root(struct super_block *sb,
        return inode;
 }
 
+/*
+ * Hugetlbfs is not reclaimable; therefore its i_mmap_mutex will never
+ * be taken from reclaim -- unlike regular filesystems. This needs an
+ * annotation because huge_pmd_share() does an allocation under
+ * i_mmap_mutex.
+ */
+struct lock_class_key hugetlbfs_i_mmap_mutex_key;
+
 static struct inode *hugetlbfs_get_inode(struct super_block *sb,
                                        struct inode *dir,
                                        umode_t mode, dev_t dev)
@@ -474,6 +482,8 @@ static struct inode *hugetlbfs_get_inode(struct super_block *sb,
                struct hugetlbfs_inode_info *info;
                inode->i_ino = get_next_ino();
                inode_init_owner(inode, dir, mode);
+               lockdep_set_class(&inode->i_mapping->i_mmap_mutex,
+                               &hugetlbfs_i_mmap_mutex_key);
                inode->i_mapping->a_ops = &hugetlbfs_aops;
                inode->i_mapping->backing_dev_info =&hugetlbfs_backing_dev_info;
                inode->i_atime = inode->i_mtime = inode->i_ctime = CURRENT_TIME;