shmem: support RENAME_EXCHANGE

This is really simple in tmpfs since the VFS already takes care of
shuffling the dentries.  Just adjust nlink on parent directories and touch
c & mtimes.

Signed-off-by: Miklos Szeredi <mszeredi@suse.cz>
Acked-by: Hugh Dickins <hughd@google.com>
Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

diff --git a/mm/shmem.c b/mm/shmem.c
index fe959181f9950ebc5c4bcb980edf8997d1e2c6e5..0f018002dd64ebe81bb857c2cf640ae7e5dc6cd1 100644 (file)
--- a/mm/shmem.c
+++ b/mm/shmem.c
@@ -2048,6 +2048,28 @@ static int shmem_rmdir(struct inode *dir, struct dentry *dentry)
        return shmem_unlink(dir, dentry);
 }
 
+static int shmem_exchange(struct inode *old_dir, struct dentry *old_dentry, struct inode *new_dir, struct dentry *new_dentry)
+{
+       bool old_is_dir = S_ISDIR(old_dentry->d_inode->i_mode);
+       bool new_is_dir = S_ISDIR(new_dentry->d_inode->i_mode);
+
+       if (old_dir != new_dir && old_is_dir != new_is_dir) {
+               if (old_is_dir) {
+                       drop_nlink(old_dir);
+                       inc_nlink(new_dir);
+               } else {
+                       drop_nlink(new_dir);
+                       inc_nlink(old_dir);
+               }
+       }
+       old_dir->i_ctime = old_dir->i_mtime =
+       new_dir->i_ctime = new_dir->i_mtime =
+       old_dentry->d_inode->i_ctime =
+       new_dentry->d_inode->i_ctime = CURRENT_TIME;
+
+       return 0;
+}
+
 /*
  * The VFS layer already does all the dentry stuff for rename,
  * we just have to decrement the usage count for the target if
@@ -2059,9 +2081,12 @@ static int shmem_rename2(struct inode *old_dir, struct dentry *old_dentry, struc
        struct inode *inode = old_dentry->d_inode;
        int they_are_dirs = S_ISDIR(inode->i_mode);
 
-       if (flags & ~(RENAME_NOREPLACE))
+       if (flags & ~(RENAME_NOREPLACE | RENAME_EXCHANGE))
                return -EINVAL;
 
+       if (flags & RENAME_EXCHANGE)
+               return shmem_exchange(old_dir, old_dentry, new_dir, new_dentry);
+
        if (!simple_empty(new_dentry))
                return -ENOTEMPTY;