Re: [PATCH 06/10] audit: Factor out chunk replacement code

[Jan Kara <jack@suse.cz>]

On Wed 11-07-18 10:58:24, Amir Goldstein wrote:
> On Tue, Jul 10, 2018 at 1:02 PM, Jan Kara <jack@suse.cz> wrote:
> > Chunk replacement code is very similar for the cases where we grow or
> > shrink chunk. Factor the code out into a common helper function.
> >
> > Signed-off-by: Jan Kara <jack@suse.cz>
> 
> Ack. Nice re-factoring.

Thanks. BTW, I didn't add your Acked-by tags because it wasn't obvious to
me whether you meant them as an official tag-worthy statement. So do want
me to add the tags or do you prefer to stay "anonymous reviewer" ;)?

								Honza

> 
> Thanks,
> Amir.
> 
> > ---
> >  kernel/audit_tree.c | 86 +++++++++++++++++++++++++----------------------------
> >  1 file changed, 40 insertions(+), 46 deletions(-)
> >
> > diff --git a/kernel/audit_tree.c b/kernel/audit_tree.c
> > index 6a01738d1ac2..f419fdfc25b4 100644
> > --- a/kernel/audit_tree.c
> > +++ b/kernel/audit_tree.c
> > @@ -235,6 +235,38 @@ 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)
> > +{
> > +       struct audit_tree *owner;
> > +       int i, j;
> > +
> > +       new->key = old->key;
> > +       list_replace_init(&old->trees, &new->trees);
> > +       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) {
> > +                       i--;
> > +                       continue;
> > +               }
> > +               owner = old->owners[j].owner;
> > +               new->owners[i].owner = owner;
> > +               new->owners[i].index = old->owners[j].index - j + i;
> > +               if (!owner) /* result of earlier fallback */
> > +                       continue;
> > +               get_tree(owner);
> > +               list_replace_init(&old->owners[j].list, &new->owners[i].list);
> > +       }
> > +       /*
> > +        * Make sure chunk is fully initialized before making it visible in the
> > +        * hash. Pairs with a data dependency barrier in READ_ONCE() in
> > +        * audit_tree_lookup().
> > +        */
> > +       smp_wmb();
> > +       list_replace_rcu(&old->hash, &new->hash);
> > +}
> > +
> >  static void untag_chunk(struct node *p)
> >  {
> >         struct audit_chunk *chunk = find_chunk(p);
> > @@ -242,7 +274,6 @@ static void untag_chunk(struct node *p)
> >         struct audit_chunk *new = NULL;
> >         struct audit_tree *owner;
> >         int size = chunk->count - 1;
> > -       int i, j;
> >
> >         fsnotify_get_mark(entry);
> >
> > @@ -291,38 +322,16 @@ static void untag_chunk(struct node *p)
> >
> >         chunk->dead = 1;
> >         spin_lock(&hash_lock);
> > -       new->key = chunk->key;
> > -       list_replace_init(&chunk->trees, &new->trees);
> >         if (owner->root == chunk) {
> >                 list_del_init(&owner->same_root);
> >                 owner->root = NULL;
> >         }
> > -
> > -       for (i = j = 0; j <= size; i++, j++) {
> > -               struct audit_tree *s;
> > -               if (&chunk->owners[j] == p) {
> > -                       list_del_init(&p->list);
> > -                       i--;
> > -                       continue;
> > -               }
> > -               s = chunk->owners[j].owner;
> > -               new->owners[i].owner = s;
> > -               new->owners[i].index = chunk->owners[j].index - j + i;
> > -               if (!s) /* result of earlier fallback */
> > -                       continue;
> > -               get_tree(s);
> > -               list_replace_init(&chunk->owners[j].list, &new->owners[i].list);
> > -       }
> > -
> > -       list_for_each_entry(owner, &new->trees, same_root)
> > -               owner->root = new;
> > +       list_del_init(&p->list);
> >         /*
> > -        * Make sure chunk is fully initialized before making it visible in the
> > -        * hash. Pairs with a data dependency barrier in READ_ONCE() in
> > -        * audit_tree_lookup().
> > +        * This has to go last when updating chunk as once replace_chunk() is
> > +        * called, new RCU readers can see the new chunk.
> >          */
> > -       smp_wmb();
> > -       list_replace_rcu(&chunk->hash, &new->hash);
> > +       replace_chunk(new, chunk, p);
> >         spin_unlock(&hash_lock);
> >         fsnotify_detach_mark(entry);
> >         mutex_unlock(&entry->group->mark_mutex);
> > @@ -399,7 +408,6 @@ static int create_chunk(struct inode *inode, struct audit_tree *tree)
> >  static int tag_chunk(struct inode *inode, struct audit_tree *tree)
> >  {
> >         struct fsnotify_mark *old_entry, *chunk_entry;
> > -       struct audit_tree *owner;
> >         struct audit_chunk *chunk, *old;
> >         struct node *p;
> >         int n;
> > @@ -464,35 +472,21 @@ static int tag_chunk(struct inode *inode, struct audit_tree *tree)
> >                 fsnotify_put_mark(old_entry);
> >                 return 0;
> >         }
> > -       chunk->key = old->key;
> > -       list_replace_init(&old->trees, &chunk->trees);
> > -       for (n = 0, p = chunk->owners; n < old->count; n++, p++) {
> > -               struct audit_tree *s = old->owners[n].owner;
> > -               p->owner = s;
> > -               p->index = old->owners[n].index;
> > -               if (!s) /* result of fallback in untag */
> > -                       continue;
> > -               get_tree(s);
> > -               list_replace_init(&old->owners[n].list, &p->list);
> > -       }
> > +       p = &chunk->owners[chunk->count - 1];
> >         p->index = (chunk->count - 1) | (1U<<31);
> >         p->owner = tree;
> >         get_tree(tree);
> >         list_add(&p->list, &tree->chunks);
> > -       list_for_each_entry(owner, &chunk->trees, same_root)
> > -               owner->root = chunk;
> >         old->dead = 1;
> >         if (!tree->root) {
> >                 tree->root = chunk;
> >                 list_add(&tree->same_root, &chunk->trees);
> >         }
> >         /*
> > -        * Make sure chunk is fully initialized before making it visible in the
> > -        * hash. Pairs with a data dependency barrier in READ_ONCE() in
> > -        * audit_tree_lookup().
> > +        * This has to go last when updating chunk as once replace_chunk() is
> > +        * called, new RCU readers can see the new chunk.
> >          */
> > -       smp_wmb();
> > -       list_replace_rcu(&old->hash, &chunk->hash);
> > +       replace_chunk(chunk, old, NULL);
> >         spin_unlock(&hash_lock);
> >         fsnotify_detach_mark(old_entry);
> >         mutex_unlock(&audit_tree_group->mark_mutex);
> > --
> > 2.16.4
> >
-- 
Jan Kara <jack@suse.com>
SUSE Labs, CR