linux-kernel - Re: [PATCH v9 19/20] fs/dax: Properly refcount fs dax pages

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Message-ID: <964e8991-44c0-4ff7-91cc-033ed7c09835@redhat.com>
Date: Mon, 3 Mar 2025 09:58:15 +0100
From: David Hildenbrand <david@...hat.com>
To: Alistair Popple <apopple@...dia.com>, akpm@...ux-foundation.org,
 dan.j.williams@...el.com, linux-mm@...ck.org
Cc: Alison Schofield <alison.schofield@...el.com>, lina@...hilina.net,
 zhang.lyra@...il.com, gerald.schaefer@...ux.ibm.com,
 vishal.l.verma@...el.com, dave.jiang@...el.com, logang@...tatee.com,
 bhelgaas@...gle.com, jack@...e.cz, jgg@...pe.ca, catalin.marinas@....com,
 will@...nel.org, mpe@...erman.id.au, npiggin@...il.com,
 dave.hansen@...ux.intel.com, ira.weiny@...el.com, willy@...radead.org,
 djwong@...nel.org, tytso@....edu, linmiaohe@...wei.com, peterx@...hat.com,
 linux-doc@...r.kernel.org, linux-kernel@...r.kernel.org,
 linux-arm-kernel@...ts.infradead.org, linuxppc-dev@...ts.ozlabs.org,
 nvdimm@...ts.linux.dev, linux-cxl@...r.kernel.org,
 linux-fsdevel@...r.kernel.org, linux-ext4@...r.kernel.org,
 linux-xfs@...r.kernel.org, jhubbard@...dia.com, hch@....de,
 david@...morbit.com, chenhuacai@...nel.org, kernel@...0n.name,
 loongarch@...ts.linux.dev
Subject: Re: [PATCH v9 19/20] fs/dax: Properly refcount fs dax pages


> -static inline unsigned long dax_folio_share_put(struct folio *folio)
> +static inline unsigned long dax_folio_put(struct folio *folio)
>   {
> -	return --folio->page.share;
> +	unsigned long ref;
> +	int order, i;
> +
> +	if (!dax_folio_is_shared(folio))
> +		ref = 0;
> +	else
> +		ref = --folio->share;
> +

It would still be good to learn how this non-atomic update here is safe 
(@Dan?), but that's independent of this series.

Staring at it, I would have thought we have to us an atomic_t here.

Acked-by: David Hildenbrand <david@...hat.com>

-- 
Cheers,

David / dhildenb