Re: [PATCH 11/14] audit: Drop all unused chunk nodes during deletion

[Jan Kara <jack@suse.cz>]

On Tue 06-11-18 09:14:55, Paul Moore wrote:
> On Wed, Oct 17, 2018 at 6:15 AM Jan Kara <jack@suse.cz> wrote:
> > When deleting chunk from a tree, drop all unused nodes in a chunk
> > instead of just the one used by the tree. This gets rid of possibly
> > lingering unused nodes (created due to fallback path in untag_chunk())
> > and also removes some special cases and will allow us to simplify
> > locking in untag_chunk().
> >
> > Signed-off-by: Jan Kara <jack@suse.cz>
> > ---
> >  kernel/audit_tree.c | 27 ++++++++++++++++++---------
> >  1 file changed, 18 insertions(+), 9 deletions(-)
> 
> Hmmm, it looks like this is the patch which makes the list
> replace->splice change okay, yes?  If so, should this change be
> squashed into the replace_chunk() patch?

No, this change is completely unrelated to that. This is really only about
making untag_chunk() cleanup less dependent on previous context so we can
simplify the code and locking.

								Honza

> 
> > diff --git a/kernel/audit_tree.c b/kernel/audit_tree.c
> > index ca2b6baff7aa..145e8c92dd31 100644
> > --- a/kernel/audit_tree.c
> > +++ b/kernel/audit_tree.c
> > @@ -277,8 +277,7 @@ static struct audit_chunk *find_chunk(struct node *p)
> >         return container_of(p, struct audit_chunk, owners[0]);
> >  }
> >
> > -static void replace_chunk(struct audit_chunk *new, struct audit_chunk *old,
> > -                         struct node *skip)
> > +static void replace_chunk(struct audit_chunk *new, struct audit_chunk *old)
> >  {
> >         struct audit_tree *owner;
> >         int i, j;
> > @@ -288,7 +287,7 @@ static void replace_chunk(struct audit_chunk *new, struct audit_chunk *old,
> >         list_for_each_entry(owner, &new->trees, same_root)
> >                 owner->root = new;
> >         for (i = j = 0; j < old->count; i++, j++) {
> > -               if (&old->owners[j] == skip) {
> > +               if (!old->owners[j].owner) {
> >                         i--;
> >                         continue;
> >                 }
> > @@ -322,20 +321,28 @@ static void remove_chunk_node(struct audit_chunk *chunk, struct node *p)
> >         put_tree(owner);
> >  }
> >
> > +static int chunk_count_trees(struct audit_chunk *chunk)
> > +{
> > +       int i;
> > +       int ret = 0;
> > +
> > +       for (i = 0; i < chunk->count; i++)
> > +               if (chunk->owners[i].owner)
> > +                       ret++;
> > +       return ret;
> > +}
> > +
> >  static void untag_chunk(struct node *p)
> >  {
> >         struct audit_chunk *chunk = find_chunk(p);
> >         struct fsnotify_mark *entry = chunk->mark;
> >         struct audit_chunk *new = NULL;
> > -       int size = chunk->count - 1;
> > +       int size;
> >
> >         remove_chunk_node(chunk, p);
> >         fsnotify_get_mark(entry);
> >         spin_unlock(&hash_lock);
> >
> > -       if (size)
> > -               new = alloc_chunk(size);
> > -
> >         mutex_lock(&entry->group->mark_mutex);
> >         /*
> >          * mark_mutex protects mark from getting detached and thus also from
> > @@ -348,6 +355,7 @@ static void untag_chunk(struct node *p)
> >                 goto out;
> >         }
> >
> > +       size = chunk_count_trees(chunk);
> >         if (!size) {
> >                 chunk->dead = 1;
> >                 spin_lock(&hash_lock);
> > @@ -360,6 +368,7 @@ static void untag_chunk(struct node *p)
> >                 goto out;
> >         }
> >
> > +       new = alloc_chunk(size);
> >         if (!new)
> >                 goto out_mutex;
> >
> > @@ -375,7 +384,7 @@ static void untag_chunk(struct node *p)
> >          * This has to go last when updating chunk as once replace_chunk() is
> >          * called, new RCU readers can see the new chunk.
> >          */
> > -       replace_chunk(new, chunk, p);
> > +       replace_chunk(new, chunk);
> >         spin_unlock(&hash_lock);
> >         fsnotify_detach_mark(entry);
> >         mutex_unlock(&entry->group->mark_mutex);
> > @@ -520,7 +529,7 @@ static int tag_chunk(struct inode *inode, struct audit_tree *tree)
> >          * This has to go last when updating chunk as once replace_chunk() is
> >          * called, new RCU readers can see the new chunk.
> >          */
> > -       replace_chunk(chunk, old, NULL);
> > +       replace_chunk(chunk, old);
> >         spin_unlock(&hash_lock);
> >         fsnotify_detach_mark(old_entry);
> >         mutex_unlock(&audit_tree_group->mark_mutex);
> > --
> > 2.16.4
> >
> 
> 
> -- 
> paul moore
> www.paul-moore.com
-- 
Jan Kara <jack@suse.com>
SUSE Labs, CR