Re: [PATCH] mm: vmalloc: annotate find_vmap_area_exceed_addr_lock() for lockdep

[Uladzislau Rezki <urezki@gmail.com>]

On Wed, Mar 27, 2024 at 10:22:38AM -0700, Omar Sandoval wrote:
> On Wed, Mar 27, 2024 at 06:04:59PM +0100, Uladzislau Rezki wrote:
> > Hello, Jens, Omar!
> > 
> > > On Tue, Mar 26, 2024 at 04:24:01PM -0600, Jens Axboe wrote:
> > > > On 3/26/24 3:25 PM, Jens Axboe wrote:
> > > > > diff --git a/mm/vmalloc.c b/mm/vmalloc.c
> > > > > index 22aa63f4ef63..26a69fa6809c 100644
> > > > > --- a/mm/vmalloc.c
> > > > > +++ b/mm/vmalloc.c
> > > > > @@ -1032,7 +1032,7 @@ find_vmap_area_exceed_addr_lock(unsigned long addr, struct vmap_area **va)
> > > > >  	for (i = 0; i < nr_vmap_nodes; i++) {
> > > > >  		vn = &vmap_nodes[i];
> > > > >  
> > > > > -		spin_lock(&vn->busy.lock);
> > > > > +		spin_lock_nested(&vn->busy.lock, i);
> > > > >  		va_lowest = __find_vmap_area_exceed_addr(addr, &vn->busy.root);
> > > > >  		if (va_lowest) {
> > > > >  			if (!va_node || va_lowest->va_start < (*va)->va_start) {
> > > > 
> > > > Omar said he tested this and ran into lockdep complaining as it only
> > > > supports 8 subclasses. So this patch can't work, but that still leaves
> > > > the current kernel code buggy...
> > > > 	
> > > It is a bit tricky. Let me rewrite it so a lockdep does not complain.
> > > 
> > > Thank you for your report.
> > > 
> > 
> > Could you please check and test below? It is based on latest 6.9-rc1 tip.
> > I have reworked it a bit and now it does not hold two locks so the lockdep
> > should not complain.
> 
> Works here, too.
> 
> Tested-by: Omar Sandoval <osandov@fb.com>
>
Good!

I will send out the fix.

Thank you.

--
Uladzislau Rezki