1 files changed, 81 insertions, 0 deletions

diff --git a/mm/shmem.c b/mm/shmem.c
index bb8ca7ef7094..b378f66cf2f9 100644
--- a/mm/shmem.c
+++ b/mm/shmem.c
@@ -1362,6 +1362,7 @@ shmem_get_inode(struct super_block *sb, int mode, dev_t dev)
 		inode->i_mapping->a_ops = &shmem_aops;
 		inode->i_mapping->backing_dev_info = &shmem_backing_dev_info;
 		inode->i_atime = inode->i_mtime = inode->i_ctime = CURRENT_TIME;
+		inode->i_generation = get_seconds();
 		info = SHMEM_I(inode);
 		memset(info, 0, (char *)inode - (char *)info);
 		spin_lock_init(&info->lock);
@@ -1956,6 +1957,85 @@ static struct xattr_handler *shmem_xattr_handlers[] = {
 };
 #endif
 
+static struct dentry *shmem_get_parent(struct dentry *child)
+{
+	return ERR_PTR(-ESTALE);
+}
+
+static int shmem_match(struct inode *ino, void *vfh)
+{
+	__u32 *fh = vfh;
+	__u64 inum = fh[2];
+	inum = (inum << 32) | fh[1];
+	return ino->i_ino == inum && fh[0] == ino->i_generation;
+}
+
+static struct dentry *shmem_get_dentry(struct super_block *sb, void *vfh)
+{
+	struct dentry *de = NULL;
+	struct inode *inode;
+	__u32 *fh = vfh;
+	__u64 inum = fh[2];
+	inum = (inum << 32) | fh[1];
+
+	inode = ilookup5(sb, (unsigned long)(inum+fh[0]), shmem_match, vfh);
+	if (inode) {
+		de = d_find_alias(inode);
+		iput(inode);
+	}
+
+	return de? de: ERR_PTR(-ESTALE);
+}
+
+static struct dentry *shmem_decode_fh(struct super_block *sb, __u32 *fh,
+		int len, int type,
+		int (*acceptable)(void *context, struct dentry *de),
+		void *context)
+{
+	if (len < 3)
+		return ERR_PTR(-ESTALE);
+
+	return sb->s_export_op->find_exported_dentry(sb, fh, NULL, acceptable,
+							context);
+}
+
+static int shmem_encode_fh(struct dentry *dentry, __u32 *fh, int *len,
+				int connectable)
+{
+	struct inode *inode = dentry->d_inode;
+
+	if (*len < 3)
+		return 255;
+
+	if (hlist_unhashed(&inode->i_hash)) {
+		/* Unfortunately insert_inode_hash is not idempotent,
+		 * so as we hash inodes here rather than at creation
+		 * time, we need a lock to ensure we only try
+		 * to do it once
+		 */
+		static DEFINE_SPINLOCK(lock);
+		spin_lock(&lock);
+		if (hlist_unhashed(&inode->i_hash))
+			__insert_inode_hash(inode,
+					    inode->i_ino + inode->i_generation);
+		spin_unlock(&lock);
+	}
+
+	fh[0] = inode->i_generation;
+	fh[1] = inode->i_ino;
+	fh[2] = ((__u64)inode->i_ino) >> 32;
+
+	*len = 3;
+	return 1;
+}
+
+static struct export_operations shmem_export_ops = {
+	.get_parent     = shmem_get_parent,
+	.get_dentry     = shmem_get_dentry,
+	.encode_fh      = shmem_encode_fh,
+	.decode_fh      = shmem_decode_fh,
+};
+
 static int shmem_parse_options(char *options, int *mode, uid_t *uid,
 	gid_t *gid, unsigned long *blocks, unsigned long *inodes,
 	int *policy, nodemask_t *policy_nodes)
@@ -2128,6 +2208,7 @@ static int shmem_fill_super(struct super_block *sb,
 					&inodes, &policy, &policy_nodes))
 			return -EINVAL;
 	}
+	sb->s_export_op = &shmem_export_ops;
 #else
 	sb->s_flags |= MS_NOUSER;
 #endif