1 files changed, 455 insertions, 0 deletions
diff --git a/xenolinux-2.4.26-sparse/mm/highmem.c b/xenolinux-2.4.26-sparse/mm/highmem.c
new file mode 100644
index 0000000000..a68937452c
--- /dev/null
+++ b/xenolinux-2.4.26-sparse/mm/highmem.c
@@ -0,0 +1,455 @@
+/*
+ * High memory handling common code and variables.
+ *
+ * (C) 1999 Andrea Arcangeli, SuSE GmbH, andrea@suse.de
+ *          Gerhard Wichert, Siemens AG, Gerhard.Wichert@pdb.siemens.de
+ *
+ *
+ * Redesigned the x86 32-bit VM architecture to deal with
+ * 64-bit physical space. With current x86 CPUs this
+ * means up to 64 Gigabytes physical RAM.
+ *
+ * Rewrote high memory support to move the page cache into
+ * high memory. Implemented permanent (schedulable) kmaps
+ * based on Linus' idea.
+ *
+ * Copyright (C) 1999 Ingo Molnar <mingo@redhat.com>
+ */
+
+#include <linux/mm.h>
+#include <linux/pagemap.h>
+#include <linux/highmem.h>
+#include <linux/swap.h>
+#include <linux/slab.h>
+
+/*
+ * Virtual_count is not a pure "count".
+ *  0 means that it is not mapped, and has not been mapped
+ *    since a TLB flush - it is usable.
+ *  1 means that there are no users, but it has been mapped
+ *    since the last TLB flush - so we can't use it.
+ *  n means that there are (n-1) current users of it.
+ */
+static int pkmap_count[LAST_PKMAP];
+static unsigned int last_pkmap_nr;
+static spinlock_cacheline_t kmap_lock_cacheline = {SPIN_LOCK_UNLOCKED};
+#define kmap_lock  kmap_lock_cacheline.lock
+
+pte_t * pkmap_page_table;
+
+static DECLARE_WAIT_QUEUE_HEAD(pkmap_map_wait);
+
+static void flush_all_zero_pkmaps(void)
+{
+	int i;
+
+	flush_cache_all();
+
+	for (i = 0; i < LAST_PKMAP; i++) {
+		struct page *page;
+
+		/*
+		 * zero means we don't have anything to do,
+		 * >1 means that it is still in use. Only
+		 * a count of 1 means that it is free but
+		 * needs to be unmapped
+		 */
+		if (pkmap_count[i] != 1)
+			continue;
+		pkmap_count[i] = 0;
+
+		/* sanity check */
+		if (pte_none(pkmap_page_table[i]))
+			BUG();
+
+		/*
+		 * Don't need an atomic fetch-and-clear op here;
+		 * no-one has the page mapped, and cannot get at
+		 * its virtual address (and hence PTE) without first
+		 * getting the kmap_lock (which is held here).
+		 * So no dangers, even with speculative execution.
+		 */
+		page = pte_page(pkmap_page_table[i]);
+		pte_clear(&pkmap_page_table[i]);
+
+		page->virtual = NULL;
+	}
+	flush_tlb_all();
+}
+
+static inline unsigned long map_new_virtual(struct page *page, int nonblocking)
+{
+	unsigned long vaddr;
+	int count;
+
+start:
+	count = LAST_PKMAP;
+	/* Find an empty entry */
+	for (;;) {
+		last_pkmap_nr = (last_pkmap_nr + 1) & LAST_PKMAP_MASK;
+		if (!last_pkmap_nr) {
+			flush_all_zero_pkmaps();
+			count = LAST_PKMAP;
+		}
+		if (!pkmap_count[last_pkmap_nr])
+			break;	/* Found a usable entry */
+		if (--count)
+			continue;
+
+		if (nonblocking)
+			return 0;
+
+		/*
+		 * Sleep for somebody else to unmap their entries
+		 */
+		{
+			DECLARE_WAITQUEUE(wait, current);
+
+			current->state = TASK_UNINTERRUPTIBLE;
+			add_wait_queue(&pkmap_map_wait, &wait);
+			spin_unlock(&kmap_lock);
+			schedule();
+			remove_wait_queue(&pkmap_map_wait, &wait);
+			spin_lock(&kmap_lock);
+
+			/* Somebody else might have mapped it while we slept */
+			if (page->virtual)
+				return (unsigned long) page->virtual;
+
+			/* Re-start */
+			goto start;
+		}
+	}
+	vaddr = PKMAP_ADDR(last_pkmap_nr);
+	set_pte(&(pkmap_page_table[last_pkmap_nr]), mk_pte(page, kmap_prot));
+	XEN_flush_page_update_queue();
+
+	pkmap_count[last_pkmap_nr] = 1;
+	page->virtual = (void *) vaddr;
+
+	return vaddr;
+}
+
+void *kmap_high(struct page *page, int nonblocking)
+{
+	unsigned long vaddr;
+
+	/*
+	 * For highmem pages, we can't trust "virtual" until
+	 * after we have the lock.
+	 *
+	 * We cannot call this from interrupts, as it may block
+	 */
+	spin_lock(&kmap_lock);
+	vaddr = (unsigned long) page->virtual;
+	if (!vaddr) {
+		vaddr = map_new_virtual(page, nonblocking);
+		if (!vaddr)
+			goto out;
+	}
+	pkmap_count[PKMAP_NR(vaddr)]++;
+	if (pkmap_count[PKMAP_NR(vaddr)] < 2)
+		BUG();
+ out:
+	spin_unlock(&kmap_lock);
+	return (void*) vaddr;
+}
+
+void kunmap_high(struct page *page)
+{
+	unsigned long vaddr;
+	unsigned long nr;
+	int need_wakeup;
+
+	spin_lock(&kmap_lock);
+	vaddr = (unsigned long) page->virtual;
+	if (!vaddr)
+		BUG();
+	nr = PKMAP_NR(vaddr);
+
+	/*
+	 * A count must never go down to zero
+	 * without a TLB flush!
+	 */
+	need_wakeup = 0;
+	switch (--pkmap_count[nr]) {
+	case 0:
+		BUG();
+	case 1:
+		/*
+		 * Avoid an unnecessary wake_up() function call.
+		 * The common case is pkmap_count[] == 1, but
+		 * no waiters.
+		 * The tasks queued in the wait-queue are guarded
+		 * by both the lock in the wait-queue-head and by
+		 * the kmap_lock.  As the kmap_lock is held here,
+		 * no need for the wait-queue-head's lock.  Simply
+		 * test if the queue is empty.
+		 */
+		need_wakeup = waitqueue_active(&pkmap_map_wait);
+	}
+	spin_unlock(&kmap_lock);
+
+	/* do wake-up, if needed, race-free outside of the spin lock */
+	if (need_wakeup)
+		wake_up(&pkmap_map_wait);
+}
+
+#define POOL_SIZE 32
+
+/*
+ * This lock gets no contention at all, normally.
+ */
+static spinlock_t emergency_lock = SPIN_LOCK_UNLOCKED;
+
+int nr_emergency_pages;
+static LIST_HEAD(emergency_pages);
+
+int nr_emergency_bhs;
+static LIST_HEAD(emergency_bhs);
+
+/*
+ * Simple bounce buffer support for highmem pages.
+ * This will be moved to the block layer in 2.5.
+ */
+
+static inline void copy_from_high_bh (struct buffer_head *to,
+			 struct buffer_head *from)
+{
+	struct page *p_from;
+	char *vfrom;
+
+	p_from = from->b_page;
+
+	vfrom = kmap_atomic(p_from, KM_USER0);
+	memcpy(to->b_data, vfrom + bh_offset(from), to->b_size);
+	kunmap_atomic(vfrom, KM_USER0);
+}
+
+static inline void copy_to_high_bh_irq (struct buffer_head *to,
+			 struct buffer_head *from)
+{
+	struct page *p_to;
+	char *vto;
+	unsigned long flags;
+
+	p_to = to->b_page;
+	__save_flags(flags);
+	__cli();
+	vto = kmap_atomic(p_to, KM_BOUNCE_READ);
+	memcpy(vto + bh_offset(to), from->b_data, to->b_size);
+	kunmap_atomic(vto, KM_BOUNCE_READ);
+	__restore_flags(flags);
+}
+
+static inline void bounce_end_io (struct buffer_head *bh, int uptodate)
+{
+	struct page *page;
+	struct buffer_head *bh_orig = (struct buffer_head *)(bh->b_private);
+	unsigned long flags;
+
+	bh_orig->b_end_io(bh_orig, uptodate);
+
+	page = bh->b_page;
+
+	spin_lock_irqsave(&emergency_lock, flags);
+	if (nr_emergency_pages >= POOL_SIZE)
+		__free_page(page);
+	else {
+		/*
+		 * We are abusing page->list to manage
+		 * the highmem emergency pool:
+		 */
+		list_add(&page->list, &emergency_pages);
+		nr_emergency_pages++;
+	}
+	
+	if (nr_emergency_bhs >= POOL_SIZE) {
+#ifdef HIGHMEM_DEBUG
+		/* Don't clobber the constructed slab cache */
+		init_waitqueue_head(&bh->b_wait);
+#endif
+		kmem_cache_free(bh_cachep, bh);
+	} else {
+		/*
+		 * Ditto in the bh case, here we abuse b_inode_buffers:
+		 */
+		list_add(&bh->b_inode_buffers, &emergency_bhs);
+		nr_emergency_bhs++;
+	}
+	spin_unlock_irqrestore(&emergency_lock, flags);
+}
+
+static __init int init_emergency_pool(void)
+{
+	struct sysinfo i;
+        si_meminfo(&i);
+        si_swapinfo(&i);
+        
+        if (!i.totalhigh)
+        	return 0;
+
+	spin_lock_irq(&emergency_lock);
+	while (nr_emergency_pages < POOL_SIZE) {
+		struct page * page = alloc_page(GFP_ATOMIC);
+		if (!page) {
+			printk("couldn't refill highmem emergency pages");
+			break;
+		}
+		list_add(&page->list, &emergency_pages);
+		nr_emergency_pages++;
+	}
+	while (nr_emergency_bhs < POOL_SIZE) {
+		struct buffer_head * bh = kmem_cache_alloc(bh_cachep, SLAB_ATOMIC);
+		if (!bh) {
+			printk("couldn't refill highmem emergency bhs");
+			break;
+		}
+		list_add(&bh->b_inode_buffers, &emergency_bhs);
+		nr_emergency_bhs++;
+	}
+	spin_unlock_irq(&emergency_lock);
+	printk("allocated %d pages and %d bhs reserved for the highmem bounces\n",
+	       nr_emergency_pages, nr_emergency_bhs);
+
+	return 0;
+}
+
+__initcall(init_emergency_pool);
+
+static void bounce_end_io_write (struct buffer_head *bh, int uptodate)
+{
+	bounce_end_io(bh, uptodate);
+}
+
+static void bounce_end_io_read (struct buffer_head *bh, int uptodate)
+{
+	struct buffer_head *bh_orig = (struct buffer_head *)(bh->b_private);
+
+	if (uptodate)
+		copy_to_high_bh_irq(bh_orig, bh);
+	bounce_end_io(bh, uptodate);
+}
+
+struct page *alloc_bounce_page (void)
+{
+	struct list_head *tmp;
+	struct page *page;
+
+	page = alloc_page(GFP_NOHIGHIO);
+	if (page)
+		return page;
+	/*
+	 * No luck. First, kick the VM so it doesn't idle around while
+	 * we are using up our emergency rations.
+	 */
+	wakeup_bdflush();
+
+repeat_alloc:
+	/*
+	 * Try to allocate from the emergency pool.
+	 */
+	tmp = &emergency_pages;
+	spin_lock_irq(&emergency_lock);
+	if (!list_empty(tmp)) {
+		page = list_entry(tmp->next, struct page, list);
+		list_del(tmp->next);
+		nr_emergency_pages--;
+	}
+	spin_unlock_irq(&emergency_lock);
+	if (page)
+		return page;
+
+	/* we need to wait I/O completion */
+	run_task_queue(&tq_disk);
+
+	yield();
+	goto repeat_alloc;
+}
+
+struct buffer_head *alloc_bounce_bh (void)
+{
+	struct list_head *tmp;
+	struct buffer_head *bh;
+
+	bh = kmem_cache_alloc(bh_cachep, SLAB_NOHIGHIO);
+	if (bh)
+		return bh;
+	/*
+	 * No luck. First, kick the VM so it doesn't idle around while
+	 * we are using up our emergency rations.
+	 */
+	wakeup_bdflush();
+
+repeat_alloc:
+	/*
+	 * Try to allocate from the emergency pool.
+	 */
+	tmp = &emergency_bhs;
+	spin_lock_irq(&emergency_lock);
+	if (!list_empty(tmp)) {
+		bh = list_entry(tmp->next, struct buffer_head, b_inode_buffers);
+		list_del(tmp->next);
+		nr_emergency_bhs--;
+	}
+	spin_unlock_irq(&emergency_lock);
+	if (bh)
+		return bh;
+
+	/* we need to wait I/O completion */
+	run_task_queue(&tq_disk);
+
+	yield();
+	goto repeat_alloc;
+}
+
+struct buffer_head * create_bounce(int rw, struct buffer_head * bh_orig)
+{
+	struct page *page;
+	struct buffer_head *bh;
+
+	if (!PageHighMem(bh_orig->b_page))
+		return bh_orig;
+
+	bh = alloc_bounce_bh();
+	/*
+	 * This is wasteful for 1k buffers, but this is a stopgap measure
+	 * and we are being ineffective anyway. This approach simplifies
+	 * things immensly. On boxes with more than 4GB RAM this should
+	 * not be an issue anyway.
+	 */
+	page = alloc_bounce_page();
+
+	set_bh_page(bh, page, 0);
+
+	bh->b_next = NULL;
+	bh->b_blocknr = bh_orig->b_blocknr;
+	bh->b_size = bh_orig->b_size;
+	bh->b_list = -1;
+	bh->b_dev = bh_orig->b_dev;
+	bh->b_count = bh_orig->b_count;
+	bh->b_rdev = bh_orig->b_rdev;
+	bh->b_state = bh_orig->b_state;
+#ifdef HIGHMEM_DEBUG
+	bh->b_flushtime = jiffies;
+	bh->b_next_free = NULL;
+	bh->b_prev_free = NULL;
+	/* bh->b_this_page */
+	bh->b_reqnext = NULL;
+	bh->b_pprev = NULL;
+#endif
+	/* bh->b_page */
+	if (rw == WRITE) {
+		bh->b_end_io = bounce_end_io_write;
+		copy_from_high_bh(bh, bh_orig);
+	} else
+		bh->b_end_io = bounce_end_io_read;
+	bh->b_private = (void *)bh_orig;
+	bh->b_rsector = bh_orig->b_rsector;
+#ifdef HIGHMEM_DEBUG
+	memset(&bh->b_wait, -1, sizeof(bh->b_wait));
+#endif
+
+	return bh;
+}
+