diff options
| -rw-r--r-- | mm/highmem.c | 65 |
1 files changed, 57 insertions, 8 deletions
diff --git a/mm/highmem.c b/mm/highmem.c index b36b83b920f..910198037bf 100644 --- a/mm/highmem.c +++ b/mm/highmem.c @@ -67,6 +67,25 @@ pte_t * pkmap_page_table; static DECLARE_WAIT_QUEUE_HEAD(pkmap_map_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 + static void flush_all_zero_pkmaps(void) { int i; @@ -113,9 +132,9 @@ static void flush_all_zero_pkmaps(void) */ void kmap_flush_unused(void) { - spin_lock(&kmap_lock); + lock_kmap(); flush_all_zero_pkmaps(); - spin_unlock(&kmap_lock); + unlock_kmap(); } static inline unsigned long map_new_virtual(struct page *page) @@ -145,10 +164,10 @@ start: __set_current_state(TASK_UNINTERRUPTIBLE); add_wait_queue(&pkmap_map_wait, &wait); - spin_unlock(&kmap_lock); + unlock_kmap(); schedule(); remove_wait_queue(&pkmap_map_wait, &wait); - spin_lock(&kmap_lock); + lock_kmap(); /* Somebody else might have mapped it while we slept */ if (page_address(page)) @@ -184,29 +203,59 @@ void *kmap_high(struct page *page) * For highmem pages, we can't trust "virtual" until * after we have the lock. */ - spin_lock(&kmap_lock); + lock_kmap(); 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); - spin_unlock(&kmap_lock); + unlock_kmap(); 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. 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 + /** * kunmap_high - map 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. */ void kunmap_high(struct page *page) { unsigned long vaddr; unsigned long nr; + unsigned long flags; int need_wakeup; - spin_lock(&kmap_lock); + lock_kmap_any(flags); vaddr = (unsigned long)page_address(page); BUG_ON(!vaddr); nr = PKMAP_NR(vaddr); @@ -232,7 +281,7 @@ void kunmap_high(struct page *page) */ need_wakeup = waitqueue_active(&pkmap_map_wait); } - spin_unlock(&kmap_lock); + unlock_kmap_any(flags); /* do wake-up, if needed, race-free outside of the spin lock */ if (need_wakeup) |