Re: [PATCH 01/10] audit_tree: Remove mark->lock locking

[Jan Kara <jack@suse.cz>]

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
-- 
Jan Kara <jack@suse.com>
SUSE Labs, CR