Re: [PATCH 06/14] audit: Factor out chunk replacement code

On 2018-10-17 12:14, Jan Kara 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. Noting just the switch from list_replace_init() to list_splice_init().

Reviewed-by: Richard Guy Briggs <rgb(a)redhat.com&gt; > Signed-off-by: Jan Kara <jack(a)suse.cz&gt; > --- > 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 307749d6773c..d8f6cfa0005b 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_splice_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 > - RGB -- Richard Guy Briggs <rgb(a)redhat.com&gt; Sr. S/W Engineer, Kernel Security, Base Operating Systems Remote, Ottawa, Red Hat Canada IRC: rgb, SunRaycer Voice: +1.647.777.2635, Internal: (81) 32635