linux-kernel - Re: [PATCH 2/3] mm: Extract might

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Date:   Tue, 24 Nov 2020 11:27:39 -0400
From:   Jason Gunthorpe <jgg@...pe.ca>
To:     DRI Development <dri-devel@...ts.freedesktop.org>,
        Intel Graphics Development <intel-gfx@...ts.freedesktop.org>,
        linux-mm@...ck.org, linux-xfs@...r.kernel.org,
        linux-fsdevel@...r.kernel.org, LKML <linux-kernel@...r.kernel.org>,
        Vlastimil Babka <vbabka@...e.cz>,
        "Paul E . McKenney" <paulmck@...nel.org>,
        Christoph Lameter <cl@...ux.com>,
        Pekka Enberg <penberg@...nel.org>,
        David Rientjes <rientjes@...gle.com>,
        Joonsoo Kim <iamjoonsoo.kim@....com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Peter Zijlstra <peterz@...radead.org>,
        Ingo Molnar <mingo@...nel.org>,
        Mathieu Desnoyers <mathieu.desnoyers@...icios.com>,
        Sebastian Andrzej Siewior <bigeasy@...utronix.de>,
        Michel Lespinasse <walken@...gle.com>,
        Waiman Long <longman@...hat.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Randy Dunlap <rdunlap@...radead.org>,
        Dave Chinner <david@...morbit.com>, Qian Cai <cai@....pw>,
        "Matthew Wilcox (Oracle)" <willy@...radead.org>,
        Daniel Vetter <daniel.vetter@...el.com>
Subject: Re: [PATCH 2/3] mm: Extract might_alloc() debug check

On Tue, Nov 24, 2020 at 03:34:11PM +0100, Daniel Vetter wrote:
> On Fri, Nov 20, 2020 at 02:07:19PM -0400, Jason Gunthorpe wrote:
> > On Fri, Nov 20, 2020 at 10:54:43AM +0100, Daniel Vetter wrote:
> > > diff --git a/include/linux/sched/mm.h b/include/linux/sched/mm.h
> > > index d5ece7a9a403..f94405d43fd1 100644
> > > +++ b/include/linux/sched/mm.h
> > > @@ -180,6 +180,22 @@ static inline void fs_reclaim_acquire(gfp_t gfp_mask) { }
> > >  static inline void fs_reclaim_release(gfp_t gfp_mask) { }
> > >  #endif
> > >  
> > > +/**
> > > + * might_alloc - Marks possible allocation sites
> > > + * @gfp_mask: gfp_t flags that would be use to allocate
> > > + *
> > > + * Similar to might_sleep() and other annotations this can be used in functions
> > > + * that might allocate, but often dont. Compiles to nothing without
> > > + * CONFIG_LOCKDEP. Includes a conditional might_sleep() if @gfp allows blocking.
> > > + */
> > > +static inline void might_alloc(gfp_t gfp_mask)
> > > +{
> > > +	fs_reclaim_acquire(gfp_mask);
> > > +	fs_reclaim_release(gfp_mask);
> > > +
> > > +	might_sleep_if(gfpflags_allow_blocking(gfp_mask));
> > > +}
> > 
> > Reviewed-by: Jason Gunthorpe <jgg@...dia.com>
> > 
> > Oh, I just had a another thread with Matt about xarray, this would be
> > perfect to add before xas_nomem():
> 
> Yeah I think there's plenty of places where this will be useful. Want to
> slap a sob onto this diff so I can include it for the next round, or will
> you or Matt send this out when my might_alloc has landed?

When this is merged I can do this - just wanted to point out the API
is good and useful

Jason