From: Helge Deller <deller@gmx.de>
To: Matthew Wilcox <willy@infradead.org>,
James Bottomley <James.Bottomley@hansenpartnership.com>
Cc: Linux FS-devel Mailing List <linux-fsdevel@vger.kernel.org>,
Parisc List <linux-parisc@vger.kernel.org>,
"Aneesh Kumar K.V" <aneesh.kumar@linux.ibm.com>,
linux-nvdimm@lists.01.org
Subject: Re: PATCH] fs/dax: fix compile problem on parisc and mips
Date: Fri, 4 Dec 2020 08:57:37 +0100 [thread overview]
Message-ID: <0f0ac7be-0108-0648-a4db-2f37db1c8114@gmx.de> (raw)
In-Reply-To: <20201204034843.GM11935@casper.infradead.org>
On 12/4/20 4:48 AM, Matthew Wilcox wrote:
> On Thu, Dec 03, 2020 at 04:33:10PM -0800, James Bottomley wrote:
>> These platforms define PMD_ORDER in asm/pgtable.h
>
> I think that's the real problem, though.
>
> #define PGD_ORDER 1 /* Number of pages per pgd */
> #define PMD_ORDER 1 /* Number of pages per pmd */
> #define PGD_ALLOC_ORDER (2 + 1) /* first pgd contains pmd */
> #else
> #define PGD_ORDER 1 /* Number of pages per pgd */
> #define PGD_ALLOC_ORDER (PGD_ORDER + 1)
>
> That should clearly be PMD_ALLOC_ORDER, not PMD_ORDER. Or even
> PAGES_PER_PMD like the comment calls it, because I really think
> that doing an order-3 (8 pages) allocation for the PGD is wrong.
We need a spinlock to protect parallel accesses to the PGD,
search for pgd_spinlock().
This spinlock is stored behind the memory used for the PGD, which
is why we allocate more memory (and waste 3 pages).
Helge
next prev parent reply other threads:[~2020-12-04 7:59 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-12-04 0:33 PATCH] fs/dax: fix compile problem on parisc and mips James Bottomley
2020-12-04 3:48 ` Matthew Wilcox
2020-12-04 7:57 ` Helge Deller [this message]
2020-12-04 12:44 ` Matthew Wilcox
2020-12-04 13:28 ` John David Anglin
2020-12-04 14:11 ` Matthew Wilcox
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