linux-kernel - Re: [PATCH v6 10/16] mm: replace vm_lock and detached flag with a reference count

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite for Android: free password hash cracker in your pocket

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <CAJuCfpFeKd8T-HXx+iD3DDPe_k_vMZgDvxeVRiuHDGwwgUTfdA@mail.gmail.com>
Date: Mon, 16 Dec 2024 12:53:23 -0800
From: Suren Baghdasaryan <surenb@...gle.com>
To: Peter Zijlstra <peterz@...radead.org>
Cc: akpm@...ux-foundation.org, willy@...radead.org, liam.howlett@...cle.com, 
	lorenzo.stoakes@...cle.com, mhocko@...e.com, vbabka@...e.cz, 
	hannes@...xchg.org, mjguzik@...il.com, oliver.sang@...el.com, 
	mgorman@...hsingularity.net, david@...hat.com, peterx@...hat.com, 
	oleg@...hat.com, dave@...olabs.net, paulmck@...nel.org, brauner@...nel.org, 
	dhowells@...hat.com, hdanton@...a.com, hughd@...gle.com, 
	lokeshgidra@...gle.com, minchan@...gle.com, jannh@...gle.com, 
	shakeel.butt@...ux.dev, souravpanda@...gle.com, pasha.tatashin@...een.com, 
	klarasmodin@...il.com, corbet@....net, linux-doc@...r.kernel.org, 
	linux-mm@...ck.org, linux-kernel@...r.kernel.org, kernel-team@...roid.com
Subject: Re: [PATCH v6 10/16] mm: replace vm_lock and detached flag with a
 reference count

On Mon, Dec 16, 2024 at 12:42 PM Peter Zijlstra <peterz@...radead.org> wrote:
>
> On Mon, Dec 16, 2024 at 11:24:13AM -0800, Suren Baghdasaryan wrote:
> > @@ -734,10 +761,12 @@ static inline bool vma_start_read(struct vm_area_struct *vma)
> >        * after it has been unlocked.
> >        * This pairs with RELEASE semantics in vma_end_write_all().
> >        */
> > +     if (oldcnt & VMA_STATE_LOCKED ||
> > +         unlikely(vma->vm_lock_seq == raw_read_seqcount(&vma->vm_mm->mm_lock_seq))) {
>
> You likely want that unlikely to cover both conditions :-)

True. VMA_STATE_LOCKED is set only while the writer is updating the
vm_lock_seq and that's a narrow window. I'll make that change in the
next revision. Thanks!

>
> > +             vma_refcount_put(vma);
> >               return false;
> >       }
> > +
> >       return true;
> >  }