ocfs2: Add ioctl for reflink.

The ioctl will take 3 parameters: old_path, new_path and
preserve and call vfs_reflink. It is useful when we backport
reflink features to old kernels.

Signed-off-by: Tao Ma <tao.ma@oracle.com>

1 files changed, 166 insertions, 0 deletions

diff --git a/fs/ocfs2/refcounttree.c b/fs/ocfs2/refcounttree.c
index 7a8a384d8ad1..60287fc56bcb 100644
--- a/fs/ocfs2/refcounttree.c
+++ b/fs/ocfs2/refcounttree.c
@@ -42,6 +42,11 @@
 #include <linux/writeback.h>
 #include <linux/pagevec.h>
 #include <linux/swap.h>
+#include <linux/security.h>
+#include <linux/fsnotify.h>
+#include <linux/quotaops.h>
+#include <linux/namei.h>
+#include <linux/mount.h>
 
 struct ocfs2_cow_context {
         struct inode *inode;
@@ -4145,3 +4150,164 @@ out:
 
         return error;
 }
+
+/*
+ * Below here are the bits used by OCFS2_IOC_REFLINK() to fake
+ * sys_reflink().  This will go away when vfs_reflink() exists in
+ * fs/namei.c.
+ */
+
+/* copied from may_create in VFS. */
+static inline int ocfs2_may_create(struct inode *dir, struct dentry *child)
+{
+        if (child->d_inode)
+                return -EEXIST;
+        if (IS_DEADDIR(dir))
+                return -ENOENT;
+        return inode_permission(dir, MAY_WRITE | MAY_EXEC);
+}
+
+/* copied from user_path_parent. */
+static int ocfs2_user_path_parent(const char __user *path,
+                                  struct nameidata *nd, char **name)
+{
+        char *s = getname(path);
+        int error;
+
+        if (IS_ERR(s))
+                return PTR_ERR(s);
+
+        error = path_lookup(s, LOOKUP_PARENT, nd);
+        if (error)
+                putname(s);
+        else
+                *name = s;
+
+        return error;
+}
+
+/**
+ * ocfs2_vfs_reflink - Create a reference-counted link
+ *
+ * @old_dentry:        source dentry + inode
+ * @dir:       directory to create the target
+ * @new_dentry:        target dentry
+ * @preserve:  if true, preserve all file attributes
+ */
+int ocfs2_vfs_reflink(struct dentry *old_dentry, struct inode *dir,
+                      struct dentry *new_dentry, bool preserve)
+{
+        struct inode *inode = old_dentry->d_inode;
+        int error;
+
+        if (!inode)
+                return -ENOENT;
+
+        error = ocfs2_may_create(dir, new_dentry);
+        if (error)
+                return error;
+
+        if (dir->i_sb != inode->i_sb)
+                return -EXDEV;
+
+        /*
+         * A reflink to an append-only or immutable file cannot be created.
+         */
+        if (IS_APPEND(inode) || IS_IMMUTABLE(inode))
+                return -EPERM;
+
+        /* Only regular files can be reflinked. */
+        if (!S_ISREG(inode->i_mode))
+                return -EPERM;
+
+        /*
+         * If the caller wants to preserve ownership, they require the
+         * rights to do so.
+         */
+        if (preserve) {
+                if ((current_fsuid() != inode->i_uid) && !capable(CAP_CHOWN))
+                        return -EPERM;
+                if (!in_group_p(inode->i_gid) && !capable(CAP_CHOWN))
+                        return -EPERM;
+        }
+
+        /*
+         * If the caller is modifying any aspect of the attributes, they
+         * are not creating a snapshot.  They need read permission on the
+         * file.
+         */
+        if (!preserve) {
+                error = inode_permission(inode, MAY_READ);
+                if (error)
+                        return error;
+        }
+
+        mutex_lock(&inode->i_mutex);
+        vfs_dq_init(dir);
+        error = ocfs2_reflink(old_dentry, dir, new_dentry, preserve);
+        mutex_unlock(&inode->i_mutex);
+        if (!error)
+                fsnotify_create(dir, new_dentry);
+        return error;
+}
+/*
+ * Most codes are copied from sys_linkat.
+ */
+int ocfs2_reflink_ioctl(struct inode *inode,
+                        const char __user *oldname,
+                        const char __user *newname,
+                        bool preserve)
+{
+        struct dentry *new_dentry;
+        struct nameidata nd;
+        struct path old_path;
+        int error;
+        char *to = NULL;
+
+        if (!ocfs2_refcount_tree(OCFS2_SB(inode->i_sb)))
+                return -EOPNOTSUPP;
+
+        error = user_path_at(AT_FDCWD, oldname, 0, &old_path);
+        if (error) {
+                mlog_errno(error);
+                return error;
+        }
+
+        error = ocfs2_user_path_parent(newname, &nd, &to);
+        if (error) {
+                mlog_errno(error);
+                goto out;
+        }
+
+        error = -EXDEV;
+        if (old_path.mnt != nd.path.mnt)
+                goto out_release;
+        new_dentry = lookup_create(&nd, 0);
+        error = PTR_ERR(new_dentry);
+        if (IS_ERR(new_dentry)) {
+                mlog_errno(error);
+                goto out_unlock;
+        }
+
+        error = mnt_want_write(nd.path.mnt);
+        if (error) {
+                mlog_errno(error);
+                goto out_dput;
+        }
+
+        error = ocfs2_vfs_reflink(old_path.dentry,
+                                  nd.path.dentry->d_inode,
+                                  new_dentry, preserve);
+        mnt_drop_write(nd.path.mnt);
+out_dput:
+        dput(new_dentry);
+out_unlock:
+        mutex_unlock(&nd.path.dentry->d_inode->i_mutex);
+out_release:
+        path_put(&nd.path);
+        putname(to);
+out:
+        path_put(&old_path);
+
+        return error;
+}