Re: [PATCH v3 3/3] iova: defer maple tree erase on GFP_ATOMIC failure

[Rik van Riel]

On Tue, 2026-06-09 at 10:04 -0300, Jason Gunthorpe wrote:
> On Tue, Jun 02, 2026 at 11:35:48PM -0400, Rik van Riel wrote:
> > +/*
> > + * Remove an IOVA entry from the maple tree. Returns true on
> > success.
> > + * On failure (maple tree node allocation under GFP_ATOMIC
> > failed),
> > + * returns false — the entry remains in the tree and the caller
> > must
> > + * not free the struct iova.
> > + */
> > +static bool remove_iova(struct iova_domain *iovad, struct iova
> > *iova)
> >  {
> >  	MA_STATE(mas, &iovad->mtree, iova->pfn_lo, iova->pfn_hi);
> >  
> > @@ -165,7 +175,36 @@ static void remove_iova(struct iova_domain
> > *iovad, struct iova *iova)
> >  	if (iova->pfn_lo < iovad->dma_32bit_pfn)
> >  		iovad->max32_alloc_size = iovad->dma_32bit_pfn;
> >  
> > -	mas_store_gfp(&mas, NULL, GFP_ATOMIC);
> > +	if (mas_store_gfp(&mas, NULL, GFP_ATOMIC))
> > +		return false;
> 
> But why does it use mas_store(NULL) instead of mas_erase()? I thought
> the iova alloc/free has to be pair wise, we don't split allocations?
> 
Mas_erase() would look cleaner, indeed, and it
looks like the mas_wr_preallocate() call is
safe from atomic context, as well!

Let me give that a try tomorrow.

I'll send a v4 if that cleanup works right.

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