linux-kernel - [PATCH] mm: Remove PFN_MAP, PFN_SPECIAL, PFN_SG_CHAIN and PFN_SG

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Message-ID: <20250604032145.463934-1-apopple@nvidia.com>
Date: Wed,  4 Jun 2025 13:21:45 +1000
From: Alistair Popple <apopple@...dia.com>
To: linux-mm@...ck.org,
	akpm@...ux-foundation.org
Cc: Alistair Popple <apopple@...dia.com>,
	David Hildenbrand <david@...hat.com>,
	Christoph Hellwig <hch@....de>,
	Jason Gunthorpe <jgg@...dia.com>,
	gerald.schaefer@...ux.ibm.com,
	dan.j.williams@...el.com,
	jgg@...pe.ca,
	willy@...radead.org,
	linux-kernel@...r.kernel.org,
	nvdimm@...ts.linux.dev,
	jhubbard@...dia.com,
	zhang.lyra@...il.com,
	debug@...osinc.com,
	bjorn@...nel.org,
	balbirs@...dia.com,
	lorenzo.stoakes@...cle.com,
	John@...ves.net
Subject: [PATCH] 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").

Signed-off-by: Alistair Popple <apopple@...dia.com>
Acked-by: David Hildenbrand <david@...hat.com>
Reviewed-by: Christoph Hellwig <hch@....de>
Reviewed-by: Jason Gunthorpe <jgg@...dia.com>
Cc: gerald.schaefer@...ux.ibm.com
Cc: dan.j.williams@...el.com
Cc: jgg@...pe.ca
Cc: willy@...radead.org
Cc: david@...hat.com
Cc: linux-kernel@...r.kernel.org
Cc: nvdimm@...ts.linux.dev
Cc: jhubbard@...dia.com
Cc: hch@....de
Cc: zhang.lyra@...il.com
Cc: debug@...osinc.com
Cc: bjorn@...nel.org
Cc: balbirs@...dia.com
Cc: lorenzo.stoakes@...cle.com
Cc: John@...ves.net

---

Splitting this off from the rest of my series[1] as a separate clean-up
for consideration for the v6.16 merge window as suggested by Christoph.

[1] - https://lore.kernel.org/linux-mm/cover.541c2702181b7461b84f1a6967a3f0e823023fcc.1748500293.git-series.apopple@nvidia.com/
---
 include/linux/pfn_t.h             | 31 +++----------------------------
 mm/memory.c                       |  2 --
 tools/testing/nvdimm/test/iomap.c |  4 ----
 3 files changed, 3 insertions(+), 34 deletions(-)

diff --git a/include/linux/pfn_t.h b/include/linux/pfn_t.h
index 2d9148221e9a..46afa12eb33b 100644
--- a/include/linux/pfn_t.h
+++ b/include/linux/pfn_t.h
@@ -5,26 +5,13 @@
 
 /*
  * 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_DEV - pfn is not covered by system memmap by default
- * 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_DEV (1ULL << (BITS_PER_LONG_LONG - 3))
-#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_DEV,	"DEV" }, \
-	{ PFN_MAP,	"MAP" }
+	{ PFN_DEV,	"DEV" }
 
 static inline pfn_t __pfn_to_pfn_t(unsigned long pfn, u64 flags)
 {
@@ -46,7 +33,7 @@ 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 || (pfn.val & PFN_DEV) == 0;
+	return (pfn.val & PFN_DEV) == 0;
 }
 
 static inline unsigned long pfn_t_to_pfn(pfn_t pfn)
@@ -100,7 +87,7 @@ static inline pud_t pfn_t_pud(pfn_t pfn, pgprot_t pgprot)
 #ifdef CONFIG_ARCH_HAS_PTE_DEVMAP
 static inline bool pfn_t_devmap(pfn_t pfn)
 {
-	const u64 flags = PFN_DEV|PFN_MAP;
+	const u64 flags = PFN_DEV;
 
 	return (pfn.val & flags) == flags;
 }
@@ -116,16 +103,4 @@ pmd_t pmd_mkdevmap(pmd_t pmd);
 pud_t pud_mkdevmap(pud_t pud);
 #endif
 #endif /* CONFIG_ARCH_HAS_PTE_DEVMAP */
-
-#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 49199410805c..cc85f814bc1c 100644
--- a/mm/memory.c
+++ b/mm/memory.c
@@ -2569,8 +2569,6 @@ static bool vm_mixed_ok(struct vm_area_struct *vma, pfn_t pfn, bool mkwrite)
 		return true;
 	if (pfn_t_devmap(pfn))
 		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 e4313726fae3..ddceb04b4a9a 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);
-- 
2.47.2