From: Dan Williams <dan.j.williams@intel.com>
To: Jason Gunthorpe <jgg@ziepe.ca>, Dan Williams <dan.j.williams@intel.com>
Cc: Alistair Popple <apopple@nvidia.com>, <linux-mm@kvack.org>,
<gerald.schaefer@linux.ibm.com>, <willy@infradead.org>,
<david@redhat.com>, <linux-kernel@vger.kernel.org>,
<nvdimm@lists.linux.dev>, <linux-fsdevel@vger.kernel.org>,
<linux-ext4@vger.kernel.org>, <linux-xfs@vger.kernel.org>,
<jhubbard@nvidia.com>, <hch@lst.de>, <zhang.lyra@gmail.com>,
<debug@rivosinc.com>, <bjorn@kernel.org>, <balbirs@nvidia.com>,
<lorenzo.stoakes@oracle.com>,
<linux-arm-kernel@lists.infradead.org>,
<loongarch@lists.linux.dev>, <linuxppc-dev@lists.ozlabs.org>,
<linux-riscv@lists.infradead.org>, <linux-cxl@vger.kernel.org>,
<dri-devel@lists.freedesktop.org>, <John@groves.net>
Subject: Re: [PATCH 07/12] mm: Remove redundant pXd_devmap calls
Date: Thu, 5 Jun 2025 09:22:52 -0700 [thread overview]
Message-ID: <6841c45c490e3_2491100c2@dwillia2-xfh.jf.intel.com.notmuch> (raw)
In-Reply-To: <20250605120909.GA44681@ziepe.ca>
Jason Gunthorpe wrote:
> On Wed, Jun 04, 2025 at 07:35:24PM -0700, Dan Williams wrote:
>
> > If all dax pages are special, then vm_normal_page() should never find
> > them and gup should fail.
> >
> > ...oh, but vm_normal_page_p[mu]d() is not used in the gup path, and
> > 'special' is not set in the pte path.
>
> That seems really suboptimal?? Why would pmd and pte be different?
>
> > I think for any p[mu]d where p[mu]d_page() is ok to use should never set
> > 'special', right?
>
> There should be dedicated functions for installing pages and PFNs,
> only the PFN one would set the special bit.
>
> And certainly your tests *should* be failing as special entries should
> never ever be converted to struct page.
That's the point, the pmd and pud special bit is not considered for gup.
So fixing that requires making it not break dax, but looks like David
has a cleanup for that.
next prev parent reply other threads:[~2025-06-05 16:26 UTC|newest]
Thread overview: 59+ messages / expand[flat|nested] mbox.gz Atom feed top
2025-05-29 6:32 [PATCH 00/12] mm: Remove pXX_devmap page table bit and pfn_t type Alistair Popple
2025-05-29 6:32 ` [PATCH 01/12] mm: Remove PFN_MAP, PFN_SG_CHAIN and PFN_SG_LAST Alistair Popple
2025-05-29 11:46 ` Jonathan Cameron
2025-06-04 3:22 ` Alistair Popple
2025-05-30 9:33 ` David Hildenbrand
2025-06-02 4:54 ` Christoph Hellwig
2025-06-04 3:23 ` Alistair Popple
2025-06-03 13:34 ` Jason Gunthorpe
2025-06-04 21:05 ` Dan Williams
2025-05-29 6:32 ` [PATCH 02/12] mm: Convert pXd_devmap checks to vma_is_dax Alistair Popple
2025-05-30 9:37 ` David Hildenbrand
2025-06-12 6:55 ` Alistair Popple
2025-06-03 13:35 ` Jason Gunthorpe
2025-06-05 1:37 ` Dan Williams
2025-05-29 6:32 ` [PATCH 03/12] mm/pagewalk: Skip dax pages in pagewalk Alistair Popple
2025-05-30 9:42 ` David Hildenbrand
2025-06-03 13:36 ` Jason Gunthorpe
2025-06-05 1:59 ` Dan Williams
2025-06-05 7:46 ` Christoph Hellwig
2025-06-05 7:49 ` David Hildenbrand
2025-06-05 16:21 ` Dan Williams
2025-06-12 7:02 ` Alistair Popple
2025-06-12 8:47 ` Alistair Popple
2025-06-12 14:15 ` Lorenzo Stoakes
2025-06-12 22:50 ` Alistair Popple
2025-05-29 6:32 ` [PATCH 04/12] mm: Convert vmf_insert_mixed() from using pte_devmap to pte_special Alistair Popple
2025-06-03 13:37 ` Jason Gunthorpe
2025-06-05 2:02 ` Dan Williams
2025-05-29 6:32 ` [PATCH 05/12] mm: Remove remaining uses of PFN_DEV Alistair Popple
2025-06-03 13:38 ` Jason Gunthorpe
2025-06-05 2:02 ` Dan Williams
2025-05-29 6:32 ` [PATCH 06/12] mm/gup: Remove pXX_devmap usage from get_user_pages() Alistair Popple
2025-06-03 13:47 ` Jason Gunthorpe
2025-06-05 2:04 ` Dan Williams
2025-05-29 6:32 ` [PATCH 07/12] mm: Remove redundant pXd_devmap calls Alistair Popple
2025-05-29 11:54 ` Jonathan Cameron
2025-06-02 9:33 ` David Hildenbrand
2025-06-02 12:20 ` David Hildenbrand
2025-06-03 13:48 ` Jason Gunthorpe
2025-06-05 2:35 ` Dan Williams
2025-06-05 12:09 ` Jason Gunthorpe
2025-06-05 12:21 ` David Hildenbrand
2025-06-05 16:30 ` Dan Williams
2025-06-05 17:04 ` David Hildenbrand
2025-06-05 16:22 ` Dan Williams [this message]
2025-05-29 6:32 ` [PATCH 08/12] mm/khugepaged: Remove redundant pmd_devmap() check Alistair Popple
2025-06-02 11:45 ` David Hildenbrand
2025-06-03 13:48 ` Jason Gunthorpe
2025-05-29 6:32 ` [PATCH 09/12] powerpc: Remove checks for devmap pages and PMDs/PUDs Alistair Popple
2025-06-03 13:49 ` Jason Gunthorpe
2025-05-29 6:32 ` [PATCH 10/12] mm: Remove devmap related functions and page table bits Alistair Popple
2025-06-03 13:50 ` Jason Gunthorpe
2025-05-29 6:32 ` [PATCH 11/12] mm: Remove callers of pfn_t functionality Alistair Popple
2025-06-02 4:44 ` Michael Kelley
2025-06-03 13:50 ` Jason Gunthorpe
2025-05-29 6:32 ` [PATCH 12/12] mm/memremap: Remove unused devmap_managed_key Alistair Popple
2025-06-03 13:51 ` Jason Gunthorpe
2025-06-02 10:31 ` [PATCH 00/12] mm: Remove pXX_devmap page table bit and pfn_t type David Hildenbrand
2025-06-05 1:39 ` Dan Williams
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