linux-kernel - [PATCH v2 12/14] mm: Remove PFN_MAP, PFN_SPECIAL, PFN_SG_CHAIN and PFN_SG

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Message-ID: <3a43a99bb4b34567bed3bfe60c9ae3533aac100d.1750075065.git-series.apopple@nvidia.com>
Date: Mon, 16 Jun 2025 21:58:14 +1000
From: Alistair Popple <apopple@...dia.com>
To: akpm@...ux-foundation.org
Cc: linux-mm@...ck.org,
	Alistair Popple <apopple@...dia.com>,
	gerald.schaefer@...ux.ibm.com,
	dan.j.williams@...el.com,
	jgg@...pe.ca,
	willy@...radead.org,
	david@...hat.com,
	linux-kernel@...r.kernel.org,
	nvdimm@...ts.linux.dev,
	linux-fsdevel@...r.kernel.org,
	linux-ext4@...r.kernel.org,
	linux-xfs@...r.kernel.org,
	jhubbard@...dia.com,
	hch@....de,
	zhang.lyra@...il.com,
	debug@...osinc.com,
	bjorn@...nel.org,
	balbirs@...dia.com,
	lorenzo.stoakes@...cle.com,
	linux-arm-kernel@...ts.infradead.org,
	loongarch@...ts.linux.dev,
	linuxppc-dev@...ts.ozlabs.org,
	linux-riscv@...ts.infradead.org,
	linux-cxl@...r.kernel.org,
	dri-devel@...ts.freedesktop.org,
	John@...ves.net,
	m.szyprowski@...sung.com,
	Jason Gunthorpe <jgg@...dia.com>
Subject: [PATCH v2 12/14] mm: Remove PFN_MAP, PFN_SPECIAL, PFN_SG_CHAIN and PFN_SG_LAST

The PFN_MAP flag is no longer used for anything, so remove it.
The PFN_SG_CHAIN and PFN_SG_LAST flags never appear to have been
used so also remove them. The last user of PFN_SPECIAL was removed
by 653d7825c149 ("dcssblk: mark DAX broken, remove FS_DAX_LIMITED
support").

Acked-by: David Hildenbrand <david@...hat.com>
Reviewed-by: Christoph Hellwig <hch@....de>
Reviewed-by: Jason Gunthorpe <jgg@...dia.com>
Reviewed-by: Dan Williams <dan.j.williams@...el.com>
Signed-off-by: Alistair Popple <apopple@...dia.com>

---

Changes since v1:

 - Moved this later in series, after PFN_DEV has been removed. This
   should solve an issue reported by Marek[1] on RISC-V (and probably
   Loongarch and others where pte_devmap() didn't imply pte_special())

[1] - https://lore.kernel.org/linux-mm/957c0d9d-2c37-4d5f-a8b8-8bf90cd0aedb@samsung.com/
---
 include/linux/pfn_t.h             | 27 ++-------------------------
 mm/memory.c                       |  2 --
 tools/testing/nvdimm/test/iomap.c |  4 ----
 3 files changed, 2 insertions(+), 31 deletions(-)

diff --git a/include/linux/pfn_t.h b/include/linux/pfn_t.h
index 2869095..2c00293 100644
--- a/include/linux/pfn_t.h
+++ b/include/linux/pfn_t.h
@@ -5,23 +5,11 @@
 
 /*
  * PFN_FLAGS_MASK - mask of all the possible valid pfn_t flags
- * PFN_SG_CHAIN - pfn is a pointer to the next scatterlist entry
- * PFN_SG_LAST - pfn references a page and is the last scatterlist entry
- * PFN_MAP - pfn has a dynamic page mapping established by a device driver
- * PFN_SPECIAL - for CONFIG_FS_DAX_LIMITED builds to allow XIP, but not
- *		 get_user_pages
  */
 #define PFN_FLAGS_MASK (((u64) (~PAGE_MASK)) << (BITS_PER_LONG_LONG - PAGE_SHIFT))
-#define PFN_SG_CHAIN (1ULL << (BITS_PER_LONG_LONG - 1))
-#define PFN_SG_LAST (1ULL << (BITS_PER_LONG_LONG - 2))
-#define PFN_MAP (1ULL << (BITS_PER_LONG_LONG - 4))
-#define PFN_SPECIAL (1ULL << (BITS_PER_LONG_LONG - 5))
 
 #define PFN_FLAGS_TRACE \
-	{ PFN_SPECIAL,	"SPECIAL" }, \
-	{ PFN_SG_CHAIN,	"SG_CHAIN" }, \
-	{ PFN_SG_LAST,	"SG_LAST" }, \
-	{ PFN_MAP,	"MAP" }
+	{ }
 
 static inline pfn_t __pfn_to_pfn_t(unsigned long pfn, u64 flags)
 {
@@ -43,7 +31,7 @@ static inline pfn_t phys_to_pfn_t(phys_addr_t addr, u64 flags)
 
 static inline bool pfn_t_has_page(pfn_t pfn)
 {
-	return (pfn.val & PFN_MAP) == PFN_MAP;
+	return true;
 }
 
 static inline unsigned long pfn_t_to_pfn(pfn_t pfn)
@@ -94,15 +82,4 @@ static inline pud_t pfn_t_pud(pfn_t pfn, pgprot_t pgprot)
 #endif
 #endif
 
-#ifdef CONFIG_ARCH_HAS_PTE_SPECIAL
-static inline bool pfn_t_special(pfn_t pfn)
-{
-	return (pfn.val & PFN_SPECIAL) == PFN_SPECIAL;
-}
-#else
-static inline bool pfn_t_special(pfn_t pfn)
-{
-	return false;
-}
-#endif /* CONFIG_ARCH_HAS_PTE_SPECIAL */
 #endif /* _LINUX_PFN_T_H_ */
diff --git a/mm/memory.c b/mm/memory.c
index f69e66d..f1d81ad 100644
--- a/mm/memory.c
+++ b/mm/memory.c
@@ -2581,8 +2581,6 @@ static bool vm_mixed_ok(struct vm_area_struct *vma, pfn_t pfn, bool mkwrite)
 	/* these checks mirror the abort conditions in vm_normal_page */
 	if (vma->vm_flags & VM_MIXEDMAP)
 		return true;
-	if (pfn_t_special(pfn))
-		return true;
 	if (is_zero_pfn(pfn_t_to_pfn(pfn)))
 		return true;
 	return false;
diff --git a/tools/testing/nvdimm/test/iomap.c b/tools/testing/nvdimm/test/iomap.c
index e431372..ddceb04 100644
--- a/tools/testing/nvdimm/test/iomap.c
+++ b/tools/testing/nvdimm/test/iomap.c
@@ -137,10 +137,6 @@ EXPORT_SYMBOL_GPL(__wrap_devm_memremap_pages);
 
 pfn_t __wrap_phys_to_pfn_t(phys_addr_t addr, unsigned long flags)
 {
-	struct nfit_test_resource *nfit_res = get_nfit_res(addr);
-
-	if (nfit_res)
-		flags &= ~PFN_MAP;
         return phys_to_pfn_t(addr, flags);
 }
 EXPORT_SYMBOL(__wrap_phys_to_pfn_t);
-- 
git-series 0.9.1