[01/10] audit_tree: Remove mark->lock locking
diff mbox

Message ID 20180710100217.12866-2-jack@suse.cz
State New
Headers show

Commit Message

Jan Kara July 10, 2018, 10:02 a.m. UTC
Currently, audit_tree code uses mark->lock to protect against detaching
of mark from an inode. In most places it however also uses
mark->group->mark_mutex (as we need to atomically replace attached
marks) and this provides protection against mark detaching as well. So
just remove protection with mark->lock from audit tree code and replace
it with mark->group->mark_mutex protection in all the places. It
simplifies the code and gets rid of some ugly catches like calling
fsnotify_add_mark_locked() with mark->lock held (which cannot sleep only
because we hold a reference to another mark attached to the same inode).

Signed-off-by: Jan Kara <jack@suse.cz>
---
 kernel/audit_tree.c | 24 ++++--------------------
 1 file changed, 4 insertions(+), 20 deletions(-)

Comments

Paul Moore July 27, 2018, 4:47 a.m. UTC | #1
On Tue, Jul 10, 2018 at 6:02 AM Jan Kara <jack@suse.cz> wrote:
> Currently, audit_tree code uses mark->lock to protect against detaching
> of mark from an inode. In most places it however also uses
> mark->group->mark_mutex (as we need to atomically replace attached
> marks) and this provides protection against mark detaching as well. So
> just remove protection with mark->lock from audit tree code and replace
> it with mark->group->mark_mutex protection in all the places. It
> simplifies the code and gets rid of some ugly catches like calling
> fsnotify_add_mark_locked() with mark->lock held (which cannot sleep only
> because we hold a reference to another mark attached to the same inode).
>
> Signed-off-by: Jan Kara <jack@suse.cz>
> ---
>  kernel/audit_tree.c | 24 ++++--------------------
>  1 file changed, 4 insertions(+), 20 deletions(-)

...

> diff --git a/kernel/audit_tree.c b/kernel/audit_tree.c
> index 02feef939560..1c82eb6674c4 100644
> --- a/kernel/audit_tree.c
> +++ b/kernel/audit_tree.c
> @@ -360,12 +355,12 @@ static int create_chunk(struct inode *inode, struct audit_tree *tree)
>                 return -ENOSPC;
>         }
>
> -       spin_lock(&entry->lock);
> +       mutex_lock(&entry->group->mark_mutex);

I wonder if we could move the lock up above the
fsnotify_add_inode_mark() earlier in create_chunk() and use
fsnotify_add_mark_locked()?

--
paul moore
www.paul-moore.com
Jan Kara Sept. 4, 2018, 9:53 a.m. UTC | #2
Hi,

sorry for getting to this so late but I was catching up after vacation and
your replies got burried in my inbox.

On Fri 27-07-18 00:47:04, Paul Moore wrote:
> On Tue, Jul 10, 2018 at 6:02 AM Jan Kara <jack@suse.cz> wrote:
> > Currently, audit_tree code uses mark->lock to protect against detaching
> > of mark from an inode. In most places it however also uses
> > mark->group->mark_mutex (as we need to atomically replace attached
> > marks) and this provides protection against mark detaching as well. So
> > just remove protection with mark->lock from audit tree code and replace
> > it with mark->group->mark_mutex protection in all the places. It
> > simplifies the code and gets rid of some ugly catches like calling
> > fsnotify_add_mark_locked() with mark->lock held (which cannot sleep only
> > because we hold a reference to another mark attached to the same inode).
> >
> > Signed-off-by: Jan Kara <jack@suse.cz>
> > ---
> >  kernel/audit_tree.c | 24 ++++--------------------
> >  1 file changed, 4 insertions(+), 20 deletions(-)
> 
> ...
> 
> > diff --git a/kernel/audit_tree.c b/kernel/audit_tree.c
> > index 02feef939560..1c82eb6674c4 100644
> > --- a/kernel/audit_tree.c
> > +++ b/kernel/audit_tree.c
> > @@ -360,12 +355,12 @@ static int create_chunk(struct inode *inode, struct audit_tree *tree)
> >                 return -ENOSPC;
> >         }
> >
> > -       spin_lock(&entry->lock);
> > +       mutex_lock(&entry->group->mark_mutex);
> 
> I wonder if we could move the lock up above the
> fsnotify_add_inode_mark() earlier in create_chunk() and use
> fsnotify_add_mark_locked()?

Possibly, but I didn't want to do this in this patch as that's a separate
change. Also this is what in fact happens in later patches.

								Honza

Patch
diff mbox

diff --git a/kernel/audit_tree.c b/kernel/audit_tree.c
index 02feef939560..1c82eb6674c4 100644
--- a/kernel/audit_tree.c
+++ b/kernel/audit_tree.c
@@ -193,7 +193,7 @@  static inline struct list_head *chunk_hash(unsigned long key)
 	return chunk_hash_heads + n % HASH_SIZE;
 }
 
-/* hash_lock & entry->lock is held by caller */
+/* hash_lock & entry->group->mark_mutex is held by caller */
 static void insert_hash(struct audit_chunk *chunk)
 {
 	unsigned long key = chunk_to_key(chunk);
@@ -256,13 +256,11 @@  static void untag_chunk(struct node *p)
 		new = alloc_chunk(size);
 
 	mutex_lock(&entry->group->mark_mutex);
-	spin_lock(&entry->lock);
 	/*
 	 * mark_mutex protects mark from getting detached and thus also from
 	 * mark->connector->obj getting NULL.
 	 */
 	if (chunk->dead || !(entry->flags & FSNOTIFY_MARK_FLAG_ATTACHED)) {
-		spin_unlock(&entry->lock);
 		mutex_unlock(&entry->group->mark_mutex);
 		if (new)
 			fsnotify_put_mark(&new->mark);
@@ -280,7 +278,6 @@  static void untag_chunk(struct node *p)
 		list_del_init(&p->list);
 		list_del_rcu(&chunk->hash);
 		spin_unlock(&hash_lock);
-		spin_unlock(&entry->lock);
 		mutex_unlock(&entry->group->mark_mutex);
 		fsnotify_destroy_mark(entry, audit_tree_group);
 		goto out;
@@ -323,7 +320,6 @@  static void untag_chunk(struct node *p)
 	list_for_each_entry(owner, &new->trees, same_root)
 		owner->root = new;
 	spin_unlock(&hash_lock);
-	spin_unlock(&entry->lock);
 	mutex_unlock(&entry->group->mark_mutex);
 	fsnotify_destroy_mark(entry, audit_tree_group);
 	fsnotify_put_mark(&new->mark);	/* drop initial reference */
@@ -340,7 +336,6 @@  static void untag_chunk(struct node *p)
 	p->owner = NULL;
 	put_tree(owner);
 	spin_unlock(&hash_lock);
-	spin_unlock(&entry->lock);
 	mutex_unlock(&entry->group->mark_mutex);
 out:
 	fsnotify_put_mark(entry);
@@ -360,12 +355,12 @@  static int create_chunk(struct inode *inode, struct audit_tree *tree)
 		return -ENOSPC;
 	}
 
-	spin_lock(&entry->lock);
+	mutex_lock(&entry->group->mark_mutex);
 	spin_lock(&hash_lock);
 	if (tree->goner) {
 		spin_unlock(&hash_lock);
 		chunk->dead = 1;
-		spin_unlock(&entry->lock);
+		mutex_unlock(&entry->group->mark_mutex);
 		fsnotify_destroy_mark(entry, audit_tree_group);
 		fsnotify_put_mark(entry);
 		return 0;
@@ -380,7 +375,7 @@  static int create_chunk(struct inode *inode, struct audit_tree *tree)
 	}
 	insert_hash(chunk);
 	spin_unlock(&hash_lock);
-	spin_unlock(&entry->lock);
+	mutex_unlock(&entry->group->mark_mutex);
 	fsnotify_put_mark(entry);	/* drop initial reference */
 	return 0;
 }
@@ -421,14 +416,12 @@  static int tag_chunk(struct inode *inode, struct audit_tree *tree)
 	chunk_entry = &chunk->mark;
 
 	mutex_lock(&old_entry->group->mark_mutex);
-	spin_lock(&old_entry->lock);
 	/*
 	 * mark_mutex protects mark from getting detached and thus also from
 	 * mark->connector->obj getting NULL.
 	 */
 	if (!(old_entry->flags & FSNOTIFY_MARK_FLAG_ATTACHED)) {
 		/* old_entry is being shot, lets just lie */
-		spin_unlock(&old_entry->lock);
 		mutex_unlock(&old_entry->group->mark_mutex);
 		fsnotify_put_mark(old_entry);
 		fsnotify_put_mark(&chunk->mark);
@@ -437,23 +430,16 @@  static int tag_chunk(struct inode *inode, struct audit_tree *tree)
 
 	if (fsnotify_add_mark_locked(chunk_entry, old_entry->connector->obj,
 				     FSNOTIFY_OBJ_TYPE_INODE, 1)) {
-		spin_unlock(&old_entry->lock);
 		mutex_unlock(&old_entry->group->mark_mutex);
 		fsnotify_put_mark(chunk_entry);
 		fsnotify_put_mark(old_entry);
 		return -ENOSPC;
 	}
 
-	/* even though we hold old_entry->lock, this is safe since chunk_entry->lock could NEVER have been grabbed before */
-	spin_lock(&chunk_entry->lock);
 	spin_lock(&hash_lock);
-
-	/* we now hold old_entry->lock, chunk_entry->lock, and hash_lock */
 	if (tree->goner) {
 		spin_unlock(&hash_lock);
 		chunk->dead = 1;
-		spin_unlock(&chunk_entry->lock);
-		spin_unlock(&old_entry->lock);
 		mutex_unlock(&old_entry->group->mark_mutex);
 
 		fsnotify_destroy_mark(chunk_entry, audit_tree_group);
@@ -485,8 +471,6 @@  static int tag_chunk(struct inode *inode, struct audit_tree *tree)
 		list_add(&tree->same_root, &chunk->trees);
 	}
 	spin_unlock(&hash_lock);
-	spin_unlock(&chunk_entry->lock);
-	spin_unlock(&old_entry->lock);
 	mutex_unlock(&old_entry->group->mark_mutex);
 	fsnotify_destroy_mark(old_entry, audit_tree_group);
 	fsnotify_put_mark(chunk_entry);	/* drop initial reference */