On Thu, Oct 18, 2018 at 3:27 PM Richard Guy Briggs <[email protected]> wrote: > 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().
Yeah, I wasn't expecting to see that, maybe it will make sense as I work through the rest of the patchset. Jan, can you explain the reason behind the change? I'm a little nervous that this is simply hiding a problem (e.g. the list_empty() check in splice). > Reviewed-by: Richard Guy Briggs <[email protected]> > > > Signed-off-by: Jan Kara <[email protected]> > > --- > > 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 <[email protected]> > 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 -- paul moore www.paul-moore.com -- Linux-audit mailing list [email protected] https://www.redhat.com/mailman/listinfo/linux-audit
