Re: [PATCH 2/3] mm: Extract might_alloc() debug check

From: Jason Gunthorpe <jgg@ziepe.ca>
To: DRI Development <dri-devel@lists.freedesktop.org>,
	Intel Graphics Development <intel-gfx@lists.freedesktop.org>,
	linux-mm@kvack.org, linux-xfs@vger.kernel.org,
	linux-fsdevel@vger.kernel.org,
	LKML <linux-kernel@vger.kernel.org>,
	Vlastimil Babka <vbabka@suse.cz>,
	"Paul E . McKenney" <paulmck@kernel.org>,
	Christoph Lameter <cl@linux.com>,
	Pekka Enberg <penberg@kernel.org>,
	David Rientjes <rientjes@google.com>,
	Joonsoo Kim <iamjoonsoo.kim@lge.com>,
	Andrew Morton <akpm@linux-foundation.org>,
	Peter Zijlstra <peterz@infradead.org>,
	Ingo Molnar <mingo@kernel.org>,
	Mathieu Desnoyers <mathieu.desnoyers@efficios.com>,
	Sebastian Andrzej Siewior <bigeasy@linutronix.de>,
	Michel Lespinasse <walken@google.com>,
	Waiman Long <longman@redhat.com>,
	Thomas Gleixner <tglx@linutronix.de>,
	Randy Dunlap <rdunlap@infradead.org>,
	Dave Chinner <david@fromorbit.com>, Qian Cai <cai@lca.pw>,
	"Matthew Wilcox (Oracle)" <willy@infradead.org>,
	Daniel Vetter <daniel.vetter@intel.com>
Subject: Re: [PATCH 2/3] mm: Extract might_alloc() debug check
Date: Tue, 24 Nov 2020 11:27:39 -0400	[thread overview]
Message-ID: <20201124152739.GF5487@ziepe.ca> (raw)
In-Reply-To: <20201124143411.GN401619@phenom.ffwll.local>

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@nvidia.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