[PATCH] [RFC, RT] fix kmap_high_get

Uwe Kleine-König
2009-08-13T21:34:03Z

This fixes the build failure with ARCH_NEEDS_KMAP_HIGH_GET.
This is only compile tested.

Signed-off-by: Uwe Kleine-König <u.kleine-koenig@pengutronix.de>
Cc: Nicolas Pitre <nico@marvell.com>
Cc: MinChan Kim <minchan.kim@gmail.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Li Zefan <lizf@cn.fujitsu.com>
Cc: Jens Axboe <jens.axboe@oracle.com>
Cc: linux-mm@kvack.org
Cc: linux-kernel@vger.kernel.org
---
Hello

this bases on the patch "[PATCH RT 9/6] [RFH] Build failure on
2.6.31-rc4-rt1 in mm/highmem.c" earlier in this thread.

I don't know if kmap_high_get() has to call kmap_account(). Anyone?

As I don't have any knowledge about highmem (or mm in general) I'll go into
hiding before tglx caughts me with his trout.

Best regards
Uwe

mm/highmem.c | 79 ++++++++++++++++++++-------------------------------------
1 files changed, 28 insertions(+), 51 deletions(-)

diff --git a/mm/highmem.c b/mm/highmem.c
index 4aa9eea..b5f5faf 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.
*
@@ -313,22 +293,32 @@ 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 kunmap_high() 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) {
atomic_t *counter = &pkmap_count[PKMAP_NR(vaddr)];
if (atomic_inc_not_zero(counter)) {
/*
- * atomic_inc_not_zero implies a (memory) barrier on success
- * so page address will be reloaded.
+ * atomic_inc_not_zero implies a (memory) barrier on
+ * success, so page address will be reloaded.
*/
- unsigned long vaddr2 = (unsigned long)page_address(page);
+ unsigned long vaddr2 =
+ (unsigned long)page_address(page);
+
if (likely(vaddr == vaddr2))
return (void *)vaddr;

@@ -344,6 +334,18 @@ again:
goto again;
}
}
+ return NULL;
+}
+
+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)
@@ -354,31 +356,6 @@ 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(atomic_read(&pkmap_count[PKMAP_NR(vaddr)]) < 1);
- atomic_add(1, pkmap_count[PKMAP_NR(vaddr)]);
- }
- unlock_kmap_any(flags);
- return (void*) vaddr;
-}
-#endif

void kunmap_high(struct page *page)
{
--
1.6.3.3

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