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Subject[PATCH] Rework kmap_high_get after kmap locking is gone
Date
This obsoletes ARCH_NEEDS_KMAP_HIGH_GET without introducing a big
overhead for the archs not having defined that symbol and removes some
duplicated code previously found in kmap_high_get and kmap_high.

Before this patch three ARM defconfigs (namely cm_x300, mv78xx0 and
stmp378x) failed to compile as the part protected by
ARCH_NEEDS_KMAP_HIGH_GET wasn't adapted by commit

b38cb5a (mm: remove kmap_lock)

Signed-off-by: Uwe Kleine-König <u.kleine-koenig@pengutronix.de>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: Thomas Gleixner <tglx@linutronix.de>
---
arch/arm/include/asm/highmem.h | 3 +-
arch/arm/mm/dma-mapping.c | 2 +-
mm/highmem.c | 89 ++++++++++++++++------------------------
3 files changed, 38 insertions(+), 56 deletions(-)

diff --git a/arch/arm/include/asm/highmem.h b/arch/arm/include/asm/highmem.h
index 7f36d00..2082ed8 100644
--- a/arch/arm/include/asm/highmem.h
+++ b/arch/arm/include/asm/highmem.h
@@ -15,10 +15,9 @@

extern pte_t *pkmap_page_table;

-#define ARCH_NEEDS_KMAP_HIGH_GET
-
extern void *kmap_high(struct page *page);
extern void *kmap_high_get(struct page *page);
+extern void kmap_high_put(struct page *page);
extern void kunmap_high(struct page *page);

extern void *kmap(struct page *page);
diff --git a/arch/arm/mm/dma-mapping.c b/arch/arm/mm/dma-mapping.c
index 1576176..4a166d9 100644
--- a/arch/arm/mm/dma-mapping.c
+++ b/arch/arm/mm/dma-mapping.c
@@ -551,7 +551,7 @@ static void dma_cache_maint_contiguous(struct page *page, unsigned long offset,
if (vaddr) {
vaddr += offset;
inner_op(vaddr, vaddr + size);
- kunmap_high(page);
+ kmap_high_put(page);
}
}

diff --git a/mm/highmem.c b/mm/highmem.c
index 446b75c..a3dd375 100644
--- a/mm/highmem.c
+++ b/mm/highmem.c
@@ -75,26 +75,6 @@ pte_t * pkmap_page_table;

static DECLARE_WAIT_QUEUE_HEAD(pkmap_wait);

-
-/*
- * 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
-
/*
* Try to free a given kmap slot.
*
@@ -313,12 +293,20 @@ static void kunmap_account(void)
wake_up(&pkmap_wait);
}

-void *kmap_high(struct page *page)
+/**
+ * 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. When and only when a non null address is returned then a
+ * matching call to kmap_high_put() is necessary.
+ *
+ * This can be called from any context.
+ */
+void *kmap_high_get(struct page *page)
{
unsigned long vaddr;

-
- kmap_account();
again:
vaddr = (unsigned long)page_address(page);
if (vaddr) {
@@ -345,6 +333,29 @@ again:
}
}

+ return NULL;
+}
+EXPORT_SYMBOL(kmap_high_get);
+
+void kmap_high_put(struct page *page)
+{
+ unsigned long vaddr = (unsigned long)page_address(page);
+
+ BUG_ON(!vaddr);
+ pkmap_put(&pkmap_count[PKMAP_NR(vaddr)]);
+}
+EXPORT_SYMBOL(kmap_high_put);
+
+void *kmap_high(struct page *page)
+{
+ unsigned long vaddr;
+
+ kmap_account();
+again:
+ vaddr = (unsigned long)kmap_high_get(page);
+ if (vaddr)
+ return (void *)vaddr;
+
vaddr = pkmap_insert(page);
if (!vaddr)
goto again;
@@ -354,37 +365,9 @@ again:

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. When and only when 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(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
-
- void kunmap_high(struct page *page)
+void kunmap_high(struct page *page)
{
- unsigned long vaddr = (unsigned long)page_address(page);
- BUG_ON(!vaddr);
- pkmap_put(&pkmap_count[PKMAP_NR(vaddr)]);
+ kmap_high_put(page);
kunmap_account();
}

--
1.6.6
--
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