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

[Daniel Vetter <daniel@ffwll.ch>]

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)))

-- 
Daniel Vetter
Software Engineer, Intel Corporation
http://blog.ffwll.ch