patches/old/proc-task_mmu-mark-devdax-and-fsdax-pages-as-always-unpinned.patch

From: Alistair Popple <apopple@nvidia.com>
Subject: proc/task_mmu: mark devdax and fsdax pages as always unpinned
Date: Tue, 7 Jan 2025 14:42:35 +1100

The procfs mmu files such as smaps and pagemap currently ignore devdax and
fsdax pages because these pages are considered special.  A future change
will start treating these as normal pages, meaning they can be exposed via
smaps and pagemap.

The only difference is that devdax and fsdax pages can never be pinned for
DMA via FOLL_LONGTERM, so add an explicit check in pte_is_pinned() to
reflect that.

Link: https://lkml.kernel.org/r/e17a04cf8feaa838e62d0c7d1de97444222b7956.1736221254.git-series.apopple@nvidia.com
Signed-off-by: Alistair Popple <apopple@nvidia.com>
Cc: Asahi Lina <lina@asahilina.net>
Cc: Bjorn Helgaas <bhelgaas@google.com>
Cc: Björn Töpel <bjorn@rivosinc.com>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Christoph Hellwig <hch@lst.de>
Cc: Chunyan Zhang <zhang.lyra@gmail.com>
Cc: Dan Wiliams <dan.j.williams@intel.com>
Cc: Darrick J. Wong <djwong@kernel.org>
Cc: Dave Chinner <david@fromorbit.com>
Cc: Dave Hansen <dave.hansen@linux.intel.com>
Cc: Dave Jiang <dave.jiang@intel.com>
Cc: David Hildenbrand <david@redhat.com>
Cc: Gerald Schaefer <gerald.schaefer@linux.ibm.com>
Cc: Ira Weiny <ira.weiny@intel.com>
Cc: Jan Kara <jack@suse.cz>
Cc: Jason Gunthorpe <jgg@nvidia.com>
Cc: Jason Gunthorpe <jgg@ziepe.ca>
Cc: John Hubbard <jhubbard@nvidia.com>
Cc: kernel test robot <lkp@intel.com>
Cc: Logan Gunthorpe <logang@deltatee.com>
Cc: Matthew Wilcox (Oracle) <willy@infradead.org>
Cc: Miaohe Lin <linmiaohe@huawei.com>
Cc: Michael Ellerman <mpe@ellerman.id.au>
Cc: Nicholas Piggin <npiggin@gmail.com>
Cc: Peter Xu <peterx@redhat.com>
Cc: Theodore Ts'o <tytso@mit.edu>
Cc: Vishal Verma <vishal.l.verma@intel.com>
Cc: Vivek Goyal <vgoyal@redhat.com>
Cc: Will Deacon <will@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---

 fs/proc/task_mmu.c |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

--- a/fs/proc/task_mmu.c~proc-task_mmu-mark-devdax-and-fsdax-pages-as-always-unpinned
+++ a/fs/proc/task_mmu.c
@@ -1378,7 +1378,7 @@ static inline bool pte_is_pinned(struct
 	if (likely(!test_bit(MMF_HAS_PINNED, &vma->vm_mm->flags)))
 		return false;
 	folio = vm_normal_folio(vma, addr, pte);
-	if (!folio)
+	if (!folio || folio_is_devdax(folio) || folio_is_fsdax(folio))
 		return false;
 	return folio_maybe_dma_pinned(folio);
 }
_