diff mbox series

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

Message ID 20201120095445.1195585-3-daniel.vetter@ffwll.ch (mailing list archive)
State New, archived
Headers show
Series mmu_notifier fs fs_reclaim lockdep annotations | expand

Commit Message

Daniel Vetter Nov. 20, 2020, 9:54 a.m. UTC 
Extracted from slab.h, which seems to have the most complete version
including the correct might_sleep() check. Roll it out to slob.c.

Motivated by a discussion with Paul about possibly changing call_rcu
behaviour to allocate memory, but only roughly every 500th call.

There are a lot fewer places in the kernel that care about whether
allocating memory is allowed or not (due to deadlocks with reclaim
code) than places that care whether sleeping is allowed. But debugging
these also tends to be a lot harder, so nice descriptive checks could
come in handy. I might have some use eventually for annotations in
drivers/gpu.

Note that unlike fs_reclaim_acquire/release gfpflags_allow_blocking
does not consult the PF_MEMALLOC flags. But there is no flag
equivalent for GFP_NOWAIT, hence this check can't go wrong due to
memalloc_no*_save/restore contexts. Willy is working on a patch series
which might change this:

https://lore.kernel.org/linux-mm/20200625113122.7540-7-willy@infradead.org/

I think best would be if that updates gfpflags_allow_blocking(), since
there's a ton of callers all over the place for that already.

Acked-by: Vlastimil Babka <vbabka@suse.cz>
Acked-by: Paul E. McKenney <paulmck@kernel.org>
Cc: Paul E. McKenney <paulmck@kernel.org>
Cc: Christoph Lameter <cl@linux.com>
Cc: Pekka Enberg <penberg@kernel.org>
Cc: David Rientjes <rientjes@google.com>
Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Vlastimil Babka <vbabka@suse.cz>
Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Cc: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Cc: Michel Lespinasse <walken@google.com>
Cc: Daniel Vetter <daniel.vetter@ffwll.ch>
Cc: Waiman Long <longman@redhat.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Randy Dunlap <rdunlap@infradead.org>
Cc: linux-mm@kvack.org
Cc: linux-fsdevel@vger.kernel.org
Cc: Dave Chinner <david@fromorbit.com>
Cc: Qian Cai <cai@lca.pw>
Cc: linux-xfs@vger.kernel.org
Cc: "Matthew Wilcox (Oracle)" <willy@infradead.org>
Signed-off-by: Daniel Vetter <daniel.vetter@intel.com>
---
 include/linux/sched/mm.h | 16 ++++++++++++++++
 mm/slab.h                |  5 +----
 mm/slob.c                |  6 ++----
 3 files changed, 19 insertions(+), 8 deletions(-)

Comments

Randy Dunlap Nov. 20, 2020, 5:19 p.m. UTC | #1 
Hi,

On 11/20/20 1:54 AM, Daniel Vetter wrote:
> diff --git a/include/linux/sched/mm.h b/include/linux/sched/mm.h
> index d5ece7a9a403..f94405d43fd1 100644
> --- a/include/linux/sched/mm.h
> +++ 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

                    Mark

> + * @gfp_mask: gfp_t flags that would be use to allocate

                                           used

> + *
> + * Similar to might_sleep() and other annotations this can be used in functions

                                         annotations,

> + * that might allocate, but often dont. Compiles to nothing without

                                     don't.

> + * CONFIG_LOCKDEP. Includes a conditional might_sleep() if @gfp allows blocking.

?                                            might_sleep_if() if

> + */
> +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));
> +}
Daniel Vetter Nov. 20, 2020, 5:31 p.m. UTC | #2 
On Fri, Nov 20, 2020 at 6:20 PM Randy Dunlap <rdunlap@infradead.org> wrote:
>
> Hi,
>
> On 11/20/20 1:54 AM, Daniel Vetter wrote:
> > diff --git a/include/linux/sched/mm.h b/include/linux/sched/mm.h
> > index d5ece7a9a403..f94405d43fd1 100644
> > --- a/include/linux/sched/mm.h
> > +++ 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
>
>                     Mark
>
> > + * @gfp_mask: gfp_t flags that would be use to allocate
>
>                                            used
>
> > + *
> > + * Similar to might_sleep() and other annotations this can be used in functions
>
>                                          annotations,
>
> > + * that might allocate, but often dont. Compiles to nothing without
>
>                                      don't.
>
> > + * CONFIG_LOCKDEP. Includes a conditional might_sleep() if @gfp allows blocking.
>
> ?                                            might_sleep_if() if

That's one if too many, I'll do the others for next round. Thanks for
taking a look.
-Daniel

>
> > + */
> > +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));
> > +}
>
>
> --
> ~Randy
>
Daniel Vetter Nov. 24, 2020, 2:34 p.m. UTC | #3 
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
> > --- a/include/linux/sched/mm.h
> > +++ 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?
-Daniel

> 
> diff --git a/lib/idr.c b/lib/idr.c
> index f4ab4f4aa3c7f5..722d9ddff53221 100644
> --- a/lib/idr.c
> +++ b/lib/idr.c
> @@ -391,6 +391,8 @@ int ida_alloc_range(struct ida *ida, unsigned int min, unsigned int max,
>  	if ((int)max < 0)
>  		max = INT_MAX;
>  
> +	might_alloc(gfp);
> +
>  retry:
>  	xas_lock_irqsave(&xas, flags);
>  next:
> diff --git a/lib/xarray.c b/lib/xarray.c
> index 5fa51614802ada..dd260ee7dcae9a 100644
> --- a/lib/xarray.c
> +++ b/lib/xarray.c
> @@ -1534,6 +1534,8 @@ void *__xa_store(struct xarray *xa, unsigned long index, void *entry, gfp_t gfp)
>  	XA_STATE(xas, xa, index);
>  	void *curr;
>  
> +	might_alloc(gfp);
> +
>  	if (WARN_ON_ONCE(xa_is_advanced(entry)))
>  		return XA_ERROR(-EINVAL);
>  	if (xa_track_free(xa) && !entry)
> @@ -1600,6 +1602,8 @@ void *__xa_cmpxchg(struct xarray *xa, unsigned long index,
>  	XA_STATE(xas, xa, index);
>  	void *curr;
>  
> +	might_alloc(gfp);
> +
>  	if (WARN_ON_ONCE(xa_is_advanced(entry)))
>  		return XA_ERROR(-EINVAL);
>  
> @@ -1637,6 +1641,8 @@ int __xa_insert(struct xarray *xa, unsigned long index, void *entry, gfp_t gfp)
>  	XA_STATE(xas, xa, index);
>  	void *curr;
>  
> +	might_alloc(gfp);
> +
>  	if (WARN_ON_ONCE(xa_is_advanced(entry)))
>  		return -EINVAL;
>  	if (!entry)
> @@ -1806,6 +1812,8 @@ int __xa_alloc(struct xarray *xa, u32 *id, void *entry,
>  {
>  	XA_STATE(xas, xa, 0);
>  
> +	might_alloc(gfp);
> +
>  	if (WARN_ON_ONCE(xa_is_advanced(entry)))
>  		return -EINVAL;
>  	if (WARN_ON_ONCE(!xa_track_free(xa)))
diff mbox series

Patch

diff --git a/include/linux/sched/mm.h b/include/linux/sched/mm.h
index d5ece7a9a403..f94405d43fd1 100644
--- a/include/linux/sched/mm.h
+++ 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));
+}
+
 /**
  * memalloc_noio_save - Marks implicit GFP_NOIO allocation scope.
  *
diff --git a/mm/slab.h b/mm/slab.h
index 6d7c6a5056ba..37b981247e5d 100644
--- a/mm/slab.h
+++ b/mm/slab.h
@@ -500,10 +500,7 @@  static inline struct kmem_cache *slab_pre_alloc_hook(struct kmem_cache *s,
 {
 	flags &= gfp_allowed_mask;
 
-	fs_reclaim_acquire(flags);
-	fs_reclaim_release(flags);
-
-	might_sleep_if(gfpflags_allow_blocking(flags));
+	might_alloc(flags);
 
 	if (should_failslab(s, flags))
 		return NULL;
diff --git a/mm/slob.c b/mm/slob.c
index 7cc9805c8091..8d4bfa46247f 100644
--- a/mm/slob.c
+++ b/mm/slob.c
@@ -474,8 +474,7 @@  __do_kmalloc_node(size_t size, gfp_t gfp, int node, unsigned long caller)
 
 	gfp &= gfp_allowed_mask;
 
-	fs_reclaim_acquire(gfp);
-	fs_reclaim_release(gfp);
+	might_alloc(gfp);
 
 	if (size < PAGE_SIZE - minalign) {
 		int align = minalign;
@@ -597,8 +596,7 @@  static void *slob_alloc_node(struct kmem_cache *c, gfp_t flags, int node)
 
 	flags &= gfp_allowed_mask;
 
-	fs_reclaim_acquire(flags);
-	fs_reclaim_release(flags);
+	might_alloc(flags);
 
 	if (c->size < PAGE_SIZE) {
 		b = slob_alloc(c->size, flags, c->align, node, 0);