patch-2.3.27 linux/mm/highmem.c

• Lines: 340
• Date: Thu Nov 11 10:33:42 1999
• Orig file: v2.3.26/linux/mm/highmem.c
• Orig date: Mon Nov 1 13:56:27 1999

diff -u --recursive --new-file v2.3.26/linux/mm/highmem.c linux/mm/highmem.c
@@ -4,19 +4,25 @@
  * (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>
 
 unsigned long highmem_mapnr;
-unsigned long nr_free_highpages = 0;
 
 struct page * prepare_highmem_swapout(struct page * page)
 {
@@ -34,9 +40,9 @@
 	if (!regular_page)
 		return NULL;
 
-	vaddr = kmap(page, KM_READ);
+	vaddr = kmap(page);
 	copy_page((void *)regular_page, (void *)vaddr);
-	kunmap(vaddr, KM_READ);
+	kunmap(page);
 
 	/*
 	 * ok, we can just forget about our highmem page since 
@@ -52,10 +58,10 @@
 	struct page *highpage;
 	unsigned long vaddr;
 
-	if (PageHighMem(page) || !nr_free_highpages)
+	if (PageHighMem(page) || !nr_free_highpages())
 		return page;
 
-	highpage = get_free_highpage(GFP_ATOMIC|__GFP_HIGHMEM);
+	highpage = alloc_page(GFP_ATOMIC|__GFP_HIGHMEM);
 	if (!highpage)
 		return page;
 	if (!PageHighMem(highpage)) {
@@ -63,9 +69,9 @@
 		return page;
 	}
 
-	vaddr = kmap(highpage, KM_WRITE);
+	vaddr = kmap(page);
 	copy_page((void *)vaddr, (void *)page_address(page));
-	kunmap(vaddr, KM_WRITE);
+	kunmap(page);
 
 	/* Preserve the caching of the swap_entry. */
 	highpage->index = page->index;
@@ -79,3 +85,275 @@
 
 	return highpage;
 }
+
+/*
+ * Right now we initialize only a single pte table. It can be extended
+ * easily, subsequent pte tables have to be allocated in one physical
+ * chunk of RAM.
+ */
+#ifdef CONFIG_X86_PAE
+#define LAST_PKMAP 2048
+#else
+#define LAST_PKMAP 4096
+#endif
+#define LAST_PKMAP_MASK (LAST_PKMAP-1)
+#define PKMAP_NR(virt)	((virt-PKMAP_BASE) >> PAGE_SHIFT)
+#define PKMAP_ADDR(nr)	(PKMAP_BASE + ((nr) << PAGE_SHIFT))
+
+/*
+ * 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 = 0;
+static spinlock_t kmap_lock;
+
+pte_t * pkmap_page_table;
+
+static DECLARE_WAIT_QUEUE_HEAD(pkmap_map_wait);
+
+static void flush_all_zero_pkmaps(void)
+{
+	int i;
+
+	for (i = 0; i < LAST_PKMAP; i++) {
+		struct page *page;
+		pte_t pte;
+		/*
+		 * 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;
+		pte = pkmap_page_table[i];
+		if (pte_none(pte))
+			continue;
+		pte_clear(pkmap_page_table+i);
+		page = pte_page(pte);
+		page->virtual = 0;
+	}
+	flush_tlb_all();
+}
+
+static unsigned long map_new_virtual(struct page *page)
+{
+	unsigned long vaddr;
+	int 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();
+		if (!pkmap_count[last_pkmap_nr])
+			break;	/* Found a usable entry */
+		if (--count)
+			continue;
+
+		/*
+		 * 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);
+			// it's not quite possible to saturate the
+			// pkmap pool right now.
+			BUG();
+			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 page->virtual;
+
+		/* Re-start */
+		count = LAST_PKMAP;
+	}
+	vaddr = PKMAP_ADDR(last_pkmap_nr);
+	pkmap_page_table[last_pkmap_nr] = mk_pte(page, kmap_prot);
+
+	/*
+	 * Subtle! For some reason if we dont do this TLB flush then
+	 * we get data corruption and weird behavior in dbench runs.
+	 * But invlpg this should not be necessery ... Any ideas?
+	 */
+	__flush_tlb_one(vaddr);
+	pkmap_count[last_pkmap_nr] = 1;
+	page->virtual = vaddr;
+
+	return vaddr;
+}
+
+unsigned long kmap_high(struct page *page)
+{
+	unsigned long vaddr;
+
+	if (!PageHighMem(page))
+		BUG();
+	/*
+	 * 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 = page->virtual;
+	if (!vaddr)
+		vaddr = map_new_virtual(page);
+	pkmap_count[PKMAP_NR(vaddr)]++;
+	if (pkmap_count[PKMAP_NR(vaddr)] < 2)
+		BUG();
+	spin_unlock(&kmap_lock);
+	return vaddr;
+}
+
+void kunmap_high(struct page *page)
+{
+	unsigned long vaddr;
+	unsigned long nr;
+
+	spin_lock(&kmap_lock);
+	vaddr = page->virtual;
+	if (!vaddr)
+		BUG();
+	nr = PKMAP_NR(vaddr);
+
+	/*
+	 * A count must never go down to zero
+	 * without a TLB flush!
+	 */
+	switch (--pkmap_count[nr]) {
+	case 0:
+		BUG();
+	case 1:
+		wake_up(&pkmap_map_wait);
+	}
+	spin_unlock(&kmap_lock);
+}
+
+/*
+ * Simple bounce buffer support for highmem pages.
+ * This will be moved to the block layer in 2.5.
+ */
+
+extern kmem_cache_t *bh_cachep;
+
+static inline void copy_from_high_bh (struct buffer_head *to,
+			 struct buffer_head *from)
+{
+	struct page *p_from;
+	unsigned long vfrom;
+
+	p_from = from->b_page;
+	vfrom = kmap_atomic(p_from, KM_BOUNCE_WRITE);
+	memcpy(to->b_data, (char *)vfrom + bh_offset(from), to->b_size);
+	kunmap_atomic(vfrom, KM_BOUNCE_WRITE);
+}
+
+static inline void copy_to_high_bh_irq (struct buffer_head *to,
+			 struct buffer_head *from)
+{
+	struct page *p_to;
+	unsigned long vto;
+
+	p_to = to->b_page;
+	vto = kmap_atomic(p_to, KM_BOUNCE_WRITE);
+	memcpy((char *)vto + bh_offset(to), from->b_data, to->b_size);
+	kunmap_atomic(vto, KM_BOUNCE_WRITE);
+}
+
+static inline void bounce_end_io (struct buffer_head *bh, int uptodate)
+{
+	struct buffer_head *bh_orig = (struct buffer_head *)(bh->b_dev_id);
+
+	bh_orig->b_end_io(bh_orig, uptodate);
+	__free_page(bh->b_page);
+	kmem_cache_free(bh_cachep, bh);
+}
+
+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_dev_id);
+
+	if (uptodate)
+		copy_to_high_bh_irq(bh_orig, bh);
+	bounce_end_io(bh, uptodate);
+}
+
+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;
+
+repeat_bh:
+	bh = kmem_cache_alloc(bh_cachep, SLAB_BUFFER);
+	if (!bh) {
+		wakeup_bdflush(1);
+		current->policy |= SCHED_YIELD;
+		schedule();
+		goto repeat_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.
+	 */
+repeat_page:
+	page = alloc_page(GFP_BUFFER);
+	if (!page) {
+		wakeup_bdflush(1);
+		current->policy |= SCHED_YIELD;
+		schedule();
+		goto repeat_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;
+	bh->b_flushtime = 0;
+	bh->b_next_free = NULL;
+	bh->b_prev_free = NULL;
+	/* bh->b_this_page */
+	bh->b_reqnext = NULL;
+	bh->b_pprev = NULL;
+	/* 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_dev_id = (void *)bh_orig;
+	bh->b_rsector = -1;
+	memset(&bh->b_wait, -1, sizeof(bh->b_wait));
+	bh->b_kiobuf = NULL;
+
+	return bh;
+}
+