[PATCH 4/4] mm: remove ARCH_NEEDS_KMAP_HIGH_GET
Arnd Bergmann
arnd at kernel.org
Sat Dec 20 03:15:59 AEDT 2025
From: Arnd Bergmann <arnd at arndb.de>
Arm has stopped setting ARCH_NEEDS_KMAP_HIGH_GET, so this
is handled using the same wrappers across all architectures
now, which leaves room for simplification.
Replace lock_kmap()/unlock_kmap() with open-coded spinlocks
and drop the now empty arch_kmap_local_high_get() and
kmap_high_unmap_local() helpers.
Signed-off-by: Arnd Bergmann <arnd at arndb.de>
---
mm/highmem.c | 100 ++++++---------------------------------------------
1 file changed, 10 insertions(+), 90 deletions(-)
diff --git a/mm/highmem.c b/mm/highmem.c
index b5c8e4c2d5d4..bdeec56471c9 100644
--- a/mm/highmem.c
+++ b/mm/highmem.c
@@ -143,25 +143,6 @@ static __cacheline_aligned_in_smp DEFINE_SPINLOCK(kmap_lock);
pte_t *pkmap_page_table;
-/*
- * Most architectures have no use for kmap_high_get(), so let's abstract
- * the disabling of IRQ out of the locking in that case to save on a
- * potential useless overhead.
- */
-#ifdef ARCH_NEEDS_KMAP_HIGH_GET
-#define lock_kmap() spin_lock_irq(&kmap_lock)
-#define unlock_kmap() spin_unlock_irq(&kmap_lock)
-#define lock_kmap_any(flags) spin_lock_irqsave(&kmap_lock, flags)
-#define unlock_kmap_any(flags) spin_unlock_irqrestore(&kmap_lock, flags)
-#else
-#define lock_kmap() spin_lock(&kmap_lock)
-#define unlock_kmap() spin_unlock(&kmap_lock)
-#define lock_kmap_any(flags) \
- do { spin_lock(&kmap_lock); (void)(flags); } while (0)
-#define unlock_kmap_any(flags) \
- do { spin_unlock(&kmap_lock); (void)(flags); } while (0)
-#endif
-
struct page *__kmap_to_page(void *vaddr)
{
unsigned long base = (unsigned long) vaddr & PAGE_MASK;
@@ -237,9 +218,9 @@ static void flush_all_zero_pkmaps(void)
void __kmap_flush_unused(void)
{
- lock_kmap();
+ spin_lock(&kmap_lock);
flush_all_zero_pkmaps();
- unlock_kmap();
+ spin_unlock(&kmap_lock);
}
static inline unsigned long map_new_virtual(struct page *page)
@@ -273,10 +254,10 @@ static inline unsigned long map_new_virtual(struct page *page)
__set_current_state(TASK_UNINTERRUPTIBLE);
add_wait_queue(pkmap_map_wait, &wait);
- unlock_kmap();
+ spin_unlock(&kmap_lock);
schedule();
remove_wait_queue(pkmap_map_wait, &wait);
- lock_kmap();
+ spin_lock(&kmap_lock);
/* Somebody else might have mapped it while we slept */
if (page_address(page))
@@ -312,60 +293,32 @@ void *kmap_high(struct page *page)
* For highmem pages, we can't trust "virtual" until
* after we have the lock.
*/
- lock_kmap();
+ spin_lock(&kmap_lock);
vaddr = (unsigned long)page_address(page);
if (!vaddr)
vaddr = map_new_virtual(page);
pkmap_count[PKMAP_NR(vaddr)]++;
BUG_ON(pkmap_count[PKMAP_NR(vaddr)] < 2);
- unlock_kmap();
+ spin_unlock(&kmap_lock);
return (void *) vaddr;
}
EXPORT_SYMBOL(kmap_high);
-#ifdef ARCH_NEEDS_KMAP_HIGH_GET
-/**
- * kmap_high_get - pin a highmem page into memory
- * @page: &struct page to pin
- *
- * Returns the page's current virtual memory address, or NULL if no mapping
- * exists. If and only if a non null address is returned then a
- * matching call to kunmap_high() is necessary.
- *
- * This can be called from any context.
- */
-void *kmap_high_get(const struct page *page)
-{
- unsigned long vaddr, flags;
-
- lock_kmap_any(flags);
- vaddr = (unsigned long)page_address(page);
- if (vaddr) {
- BUG_ON(pkmap_count[PKMAP_NR(vaddr)] < 1);
- pkmap_count[PKMAP_NR(vaddr)]++;
- }
- unlock_kmap_any(flags);
- return (void *) vaddr;
-}
-#endif
-
/**
* kunmap_high - unmap a highmem page into memory
* @page: &struct page to unmap
*
- * If ARCH_NEEDS_KMAP_HIGH_GET is not defined then this may be called
- * only from user context.
+ * This may be called only from user context.
*/
void kunmap_high(const struct page *page)
{
unsigned long vaddr;
unsigned long nr;
- unsigned long flags;
int need_wakeup;
unsigned int color = get_pkmap_color(page);
wait_queue_head_t *pkmap_map_wait;
- lock_kmap_any(flags);
+ spin_lock(&kmap_lock);
vaddr = (unsigned long)page_address(page);
BUG_ON(!vaddr);
nr = PKMAP_NR(vaddr);
@@ -392,7 +345,7 @@ void kunmap_high(const struct page *page)
pkmap_map_wait = get_pkmap_wait_queue_head(color);
need_wakeup = waitqueue_active(pkmap_map_wait);
}
- unlock_kmap_any(flags);
+ spin_unlock(&kmap_lock);
/* do wake-up, if needed, race-free outside of the spin lock */
if (need_wakeup)
@@ -507,30 +460,11 @@ static inline void kmap_local_idx_pop(void)
#define arch_kmap_local_unmap_idx(idx, vaddr) kmap_local_calc_idx(idx)
#endif
-#ifndef arch_kmap_local_high_get
-static inline void *arch_kmap_local_high_get(const struct page *page)
-{
- return NULL;
-}
-#endif
-
#ifndef arch_kmap_local_set_pte
#define arch_kmap_local_set_pte(mm, vaddr, ptep, ptev) \
set_pte_at(mm, vaddr, ptep, ptev)
#endif
-/* Unmap a local mapping which was obtained by kmap_high_get() */
-static inline bool kmap_high_unmap_local(unsigned long vaddr)
-{
-#ifdef ARCH_NEEDS_KMAP_HIGH_GET
- if (vaddr >= PKMAP_ADDR(0) && vaddr < PKMAP_ADDR(LAST_PKMAP)) {
- kunmap_high(pte_page(ptep_get(&pkmap_page_table[PKMAP_NR(vaddr)])));
- return true;
- }
-#endif
- return false;
-}
-
static pte_t *__kmap_pte;
static pte_t *kmap_get_pte(unsigned long vaddr, int idx)
@@ -574,8 +508,6 @@ EXPORT_SYMBOL_GPL(__kmap_local_pfn_prot);
void *__kmap_local_page_prot(const struct page *page, pgprot_t prot)
{
- void *kmap;
-
/*
* To broaden the usage of the actual kmap_local() machinery always map
* pages when debugging is enabled and the architecture has no problems
@@ -584,11 +516,6 @@ void *__kmap_local_page_prot(const struct page *page, pgprot_t prot)
if (!IS_ENABLED(CONFIG_DEBUG_KMAP_LOCAL_FORCE_MAP) && !PageHighMem(page))
return page_address(page);
- /* Try kmap_high_get() if architecture has it enabled */
- kmap = arch_kmap_local_high_get(page);
- if (kmap)
- return kmap;
-
return __kmap_local_pfn_prot(page_to_pfn(page), prot);
}
EXPORT_SYMBOL(__kmap_local_page_prot);
@@ -606,14 +533,7 @@ void kunmap_local_indexed(const void *vaddr)
WARN_ON_ONCE(1);
return;
}
- /*
- * Handle mappings which were obtained by kmap_high_get()
- * first as the virtual address of such mappings is below
- * PAGE_OFFSET. Warn for all other addresses which are in
- * the user space part of the virtual address space.
- */
- if (!kmap_high_unmap_local(addr))
- WARN_ON_ONCE(addr < PAGE_OFFSET);
+ WARN_ON_ONCE(addr < PAGE_OFFSET);
return;
}
--
2.39.5
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