mm: use single SWP_DEVICE_EXCLUSIVE entry type

There is no need for the distinction anymore; let's merge the readable and
writable device-exclusive entries into a single device-exclusive entry
type.

Link: https://lkml.kernel.org/r/20250210193801.781278-7-david@redhat.com
Signed-off-by: David Hildenbrand <david@redhat.com>
Acked-by: Simona Vetter <simona.vetter@ffwll.ch>
Reviewed-by: Alistair Popple <apopple@nvidia.com>
Tested-by: Alistair Popple <apopple@nvidia.com>
Cc: Alex Shi <alexs@kernel.org>
Cc: Danilo Krummrich <dakr@kernel.org>
Cc: Dave Airlie <airlied@gmail.com>
Cc: Jann Horn <jannh@google.com>
Cc: Jason Gunthorpe <jgg@nvidia.com>
Cc: Jerome Glisse <jglisse@redhat.com>
Cc: John Hubbard <jhubbard@nvidia.com>
Cc: Jonathan Corbet <corbet@lwn.net>
Cc: Karol Herbst <kherbst@redhat.com>
Cc: Liam Howlett <liam.howlett@oracle.com>
Cc: Lorenzo Stoakes <lorenzo.stoakes@oracle.com>
Cc: Lyude <lyude@redhat.com>
Cc: "Masami Hiramatsu (Google)" <mhiramat@kernel.org>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: Pasha Tatashin <pasha.tatashin@soleen.com>
Cc: Peter Xu <peterx@redhat.com>
Cc: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: SeongJae Park <sj@kernel.org>
Cc: Vlastimil Babka <vbabka@suse.cz>
Cc: Yanteng Si <si.yanteng@linux.dev>
Cc: Barry Song <v-songbaohua@oppo.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

5 files changed, 10 insertions, 39 deletions

diff --git a/include/linux/swap.h b/include/linux/swap.h
index 91b30701274e..9a48e79a0a52 100644
--- a/include/linux/swap.h
+++ b/include/linux/swap.h
@@ -74,14 +74,13 @@ static inline int current_is_kswapd(void)
  * to a special SWP_DEVICE_{READ|WRITE} entry.
  *
  * When a page is mapped by the device for exclusive access we set the CPU page
- * table entries to special SWP_DEVICE_EXCLUSIVE_* entries.
+ * table entries to a special SWP_DEVICE_EXCLUSIVE entry.
  */
 #ifdef CONFIG_DEVICE_PRIVATE
-#define SWP_DEVICE_NUM 4
+#define SWP_DEVICE_NUM 3
 #define SWP_DEVICE_WRITE (MAX_SWAPFILES+SWP_HWPOISON_NUM+SWP_MIGRATION_NUM)
 #define SWP_DEVICE_READ (MAX_SWAPFILES+SWP_HWPOISON_NUM+SWP_MIGRATION_NUM+1)
-#define SWP_DEVICE_EXCLUSIVE_WRITE (MAX_SWAPFILES+SWP_HWPOISON_NUM+SWP_MIGRATION_NUM+2)
-#define SWP_DEVICE_EXCLUSIVE_READ (MAX_SWAPFILES+SWP_HWPOISON_NUM+SWP_MIGRATION_NUM+3)
+#define SWP_DEVICE_EXCLUSIVE (MAX_SWAPFILES+SWP_HWPOISON_NUM+SWP_MIGRATION_NUM+2)
 #else
 #define SWP_DEVICE_NUM 0
 #endif
diff --git a/include/linux/swapops.h b/include/linux/swapops.h
index 96f26e29fefe..64ea151a7ae3 100644
--- a/include/linux/swapops.h
+++ b/include/linux/swapops.h
@@ -186,26 +186,16 @@ static inline bool is_writable_device_private_entry(swp_entry_t entry)
 	return unlikely(swp_type(entry) == SWP_DEVICE_WRITE);
 }
 
-static inline swp_entry_t make_readable_device_exclusive_entry(pgoff_t offset)
+static inline swp_entry_t make_device_exclusive_entry(pgoff_t offset)
 {
-	return swp_entry(SWP_DEVICE_EXCLUSIVE_READ, offset);
-}
-
-static inline swp_entry_t make_writable_device_exclusive_entry(pgoff_t offset)
-{
-	return swp_entry(SWP_DEVICE_EXCLUSIVE_WRITE, offset);
+	return swp_entry(SWP_DEVICE_EXCLUSIVE, offset);
 }
 
 static inline bool is_device_exclusive_entry(swp_entry_t entry)
 {
-	return swp_type(entry) == SWP_DEVICE_EXCLUSIVE_READ ||
-		swp_type(entry) == SWP_DEVICE_EXCLUSIVE_WRITE;
+	return swp_type(entry) == SWP_DEVICE_EXCLUSIVE;
 }
 
-static inline bool is_writable_device_exclusive_entry(swp_entry_t entry)
-{
-	return unlikely(swp_type(entry) == SWP_DEVICE_EXCLUSIVE_WRITE);
-}
 #else /* CONFIG_DEVICE_PRIVATE */
 static inline swp_entry_t make_readable_device_private_entry(pgoff_t offset)
 {
@@ -227,12 +217,7 @@ static inline bool is_writable_device_private_entry(swp_entry_t entry)
 	return false;
 }
 
-static inline swp_entry_t make_readable_device_exclusive_entry(pgoff_t offset)
-{
-	return swp_entry(0, 0);
-}
-
-static inline swp_entry_t make_writable_device_exclusive_entry(pgoff_t offset)
+static inline swp_entry_t make_device_exclusive_entry(pgoff_t offset)
 {
 	return swp_entry(0, 0);
 }
@@ -242,10 +227,6 @@ static inline bool is_device_exclusive_entry(swp_entry_t entry)
 	return false;
 }
 
-static inline bool is_writable_device_exclusive_entry(swp_entry_t entry)
-{
-	return false;
-}
 #endif /* CONFIG_DEVICE_PRIVATE */
 
 #ifdef CONFIG_MIGRATION
diff --git a/mm/mprotect.c b/mm/mprotect.c
index 516b1d847e2c..9cb6ab7c4048 100644
--- a/mm/mprotect.c
+++ b/mm/mprotect.c
@@ -225,14 +225,6 @@ static long change_pte_range(struct mmu_gather *tlb,
 				newpte = swp_entry_to_pte(entry);
 				if (pte_swp_uffd_wp(oldpte))
 					newpte = pte_swp_mkuffd_wp(newpte);
-			} else if (is_writable_device_exclusive_entry(entry)) {
-				entry = make_readable_device_exclusive_entry(
-							swp_offset(entry));
-				newpte = swp_entry_to_pte(entry);
-				if (pte_swp_soft_dirty(oldpte))
-					newpte = pte_swp_mksoft_dirty(newpte);
-				if (pte_swp_uffd_wp(oldpte))
-					newpte = pte_swp_mkuffd_wp(newpte);
 			} else if (is_pte_marker_entry(entry)) {
 				/*
 				 * Ignore error swap entries unconditionally,
diff --git a/mm/page_table_check.c b/mm/page_table_check.c
index 509c6ef8de40..c2b3600429a0 100644
--- a/mm/page_table_check.c
+++ b/mm/page_table_check.c
@@ -196,9 +196,8 @@ EXPORT_SYMBOL(__page_table_check_pud_clear);
 /* Whether the swap entry cached writable information */
 static inline bool swap_cached_writable(swp_entry_t entry)
 {
-	return is_writable_device_exclusive_entry(entry) ||
-	    is_writable_device_private_entry(entry) ||
-	    is_writable_migration_entry(entry);
+	return is_writable_device_private_entry(entry) ||
+	       is_writable_migration_entry(entry);
 }
 
 static inline void page_table_check_pte_flags(pte_t pte)
diff --git a/mm/rmap.c b/mm/rmap.c
index 0cd2a2d3de00..1129ed132af9 100644
--- a/mm/rmap.c
+++ b/mm/rmap.c
@@ -2492,7 +2492,7 @@ struct page *make_device_exclusive(struct mm_struct *mm, unsigned long addr,
 	 * do_swap_page() will trigger the conversion back while holding the
 	 * folio lock.
 	 */
-	entry = make_writable_device_exclusive_entry(page_to_pfn(page));
+	entry = make_device_exclusive_entry(page_to_pfn(page));
 	swp_pte = swp_entry_to_pte(entry);
 	if (pte_soft_dirty(fw.pte))
 		swp_pte = pte_swp_mksoft_dirty(swp_pte);