On Fri, 11 Jul 2008, Miklos Szeredi wrote:
> On Fri, 11 Jul 2008, Sage Weil wrote:
> > However, vfs_rename_dir() doesn't properly account for filesystems with
> > FS_RENAME_DOES_D_MOVE. If new_dentry has a target inode attached, it
> > unhashes the new_dentry prior to the rename() iop and rehashes it after,
> > but doesn't account for the possibility that rename() may have swapped
> > {old,new}_dentry. For FS_RENAME_DOES_D_MOVE filesystems, it rehashes
> > new_dentry (now the old renamed-from name, which d_move() expected to go
> > away), such that a subsequent lookup will find it.
> >
> > To correct this, move vfs_rename_dir()'s call to d_move() _before_ the
> > target inode mutex is dealt with. Since d_move() will have been called
> > for all filesystems at this point, there is no need to rehash new_dentry
> > unless the rename failed. (If the rename succeeded, old_dentry should
> > already be rehashed in the new location.)
>
> I think rehashing the new dentry is bogus, even on error. And it
> looks racy with lookup as well.
>
> I wonder what the original reason for that was? Git history doesn't
> tell...
I assume just to leave the dentry in the same stat we originally found it
in?
> So a better fix would be just to remove the rehashing completely.
> Does the below patch work for you?
This would work as well, yeah. I've no real preference, here...
thanks-
sage
>
> Thanks,
> Miklos
>
> ---
> fs/namei.c | 2 --
> 1 file changed, 2 deletions(-)
>
> Index: linux-2.6/fs/namei.c
> ===================================================================
> --- linux-2.6.orig/fs/namei.c 2008-07-11 22:09:32.000000000 +0200
> +++ linux-2.6/fs/namei.c 2008-07-11 22:40:16.000000000 +0200
> @@ -2643,8 +2643,6 @@ static int vfs_rename_dir(struct inode *
> if (!error)
> target->i_flags |= S_DEAD;
> mutex_unlock(&target->i_mutex);
> - if (d_unhashed(new_dentry))
> - d_rehash(new_dentry);
> dput(new_dentry);
> }
> if (!error)
> --
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