On Tue, Jul 13, 2010 at 12:49:10PM +0800, Ian Kent wrote:
> On Tue, Jun 15, 2010 at 11:39:52AM -0700, Valerie Aurora wrote:
> > Implement unioned directories, whiteouts, and fallthrus in pathname
> > lookup routines. do_lookup() and lookup_hash() call lookup_union()
> > after looking up the dentry from the top-level file system.
> > lookup_union() is centered around __lookup_hash(), which does cached
> > and/or real lookups and revalidates each dentry in the union stack.
> >
> > XXX - implement negative union cache entries
> >
> > XXX - What about different permissions on different layers on the same
> > directory name? Should complain, fail, test permissions on all
> > layers, what?
> > ---
> > fs/namei.c | 171 +++++++++++++++++++++++++++++++++++++++++++++++++++++++++++-
> > fs/union.c | 94 +++++++++++++++++++++++++++++++++
> > fs/union.h | 7 +++
> > 3 files changed, 271 insertions(+), 1 deletions(-)
> >
> > diff --git a/fs/namei.c b/fs/namei.c
> > index 06aad7e..45be5e5 100644
> > --- a/fs/namei.c
> > +++ b/fs/namei.c
> > @@ -35,6 +35,7 @@
> > #include <asm/uaccess.h>
> >
> > #include "internal.h"
> > +#include "union.h"
> >
> > /* [Feb-1997 T. Schoebel-Theuer]
> > * Fundamental changes in the pathname lookup mechanisms (namei)
> > @@ -722,6 +723,160 @@ static __always_inline void follow_dotdot(struct nameidata *nd)
> > follow_mount(&nd->path);
> > }
> >
> > +static struct dentry *__lookup_hash(struct qstr *name, struct dentry *base,
> > + struct nameidata *nd);
> > +
> > +/*
> > + * __lookup_union - Given a path from the topmost layer, lookup and
> > + * revalidate each dentry in its union stack, building it if necessary
> > + *
> > + * @nd - nameidata for the parent of @topmost
> > + * @name - pathname from this element on
> > + * @topmost - path of the topmost matching dentry
> > + *
> > + * Given the nameidata and the path of the topmost dentry for this
> > + * pathname, lookup, revalidate, and build the associated union stack.
> > + * @topmost must be either a negative dentry or a directory, and not a
> > + * whiteout.
> > + *
> > + * This function may stomp nd->path with the path of the parent
> > + * directory of lower layer, so the caller must save nd->path and
> > + * restore it afterwards. You probably want to use lookup_union(),
> > + * not __lookup_union().
> > + */
> > +
> > +static int __lookup_union(struct nameidata *nd, struct qstr *name,
> > + struct path *topmost)
> > +{
> > + struct path parent = nd->path;
> > + struct path lower, upper;
> > + struct union_dir *ud;
> > + /* new_ud is the tail of the list of union dirs for this dentry */
>
> Should new_ud be next_ud, since there is no new_ud defined?
It's also the head of the list. Good anti-comment, there. Fixed, thanks!
-VAL
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