On Wed, Sep 05, 2012 at 04:55:15PM -0400, J. Bruce Fields wrote:
> From: "J. Bruce Fields" <bfields@xxxxxxxxxx>
> diff --git a/fs/namei.c b/fs/namei.c
> index 1b46439..6156135 100644
> --- a/fs/namei.c
> +++ b/fs/namei.c
> @@ -3658,6 +3658,7 @@ static int vfs_rename_other(struct inode *old_dir, struct dentry *old_dentry,
> struct inode *new_dir, struct dentry *new_dentry)
> {
> struct inode *target = new_dentry->d_inode;
> + struct inode *source = old_dentry->d_inode;
> int error;
>
> error = security_inode_rename(old_dir, old_dentry, new_dir, new_dentry);
> @@ -3665,8 +3666,7 @@ static int vfs_rename_other(struct inode *old_dir, struct dentry *old_dentry,
> return error;
>
> dget(new_dentry);
> - if (target)
> - mutex_lock(&target->i_mutex);
> + lock_two_nondirectories(source, target);
>
> error = -EBUSY;
> if (d_mountpoint(old_dentry)||d_mountpoint(new_dentry))
> @@ -3681,8 +3681,7 @@ static int vfs_rename_other(struct inode *old_dir, struct dentry *old_dentry,
> if (!(old_dir->i_sb->s_type->fs_flags & FS_RENAME_DOES_D_MOVE))
> d_move(old_dentry, new_dentry);
> out:
> - if (target)
> - mutex_unlock(&target->i_mutex);
> + unlock_two_nondirectories(source, target);
> dput(new_dentry);
> return error;
> }
>
This change also fixes a race between rename and mount.
Apparently we avoid to rename source or target if they are
mountpoint. But nothing prevents source being the mountpoint
after d_mountpoint check because we do not hold its i_mutex.
Thus we are actually able to rename a mountpoint.
Rename directory should also need this care.
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