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