[PATCH] change gen_pool allocator to not touch managed memory

Modify the gen_pool allocator (lib/genalloc.c) to utilize a bitmap scheme
instead of the buddy scheme.  The purpose of this change is to eliminate
the touching of the actual memory being allocated.

Since the change modifies the interface, a change to the uncached allocator
(arch/ia64/kernel/uncached.c) is also required.

Both Andrey Volkov and Jes Sorenson have expressed a desire that the
gen_pool allocator not write to the memory being managed. See the
following:

  http://marc.theaimsgroup.com/?l=linux-kernel&m=113518602713125&w=2
  http://marc.theaimsgroup.com/?l=linux-kernel&m=113533568827916&w=2

Signed-off-by: Dean Nelson <dcn@sgi.com>
Cc: Andrey Volkov <avolkov@varma-el.com>
Acked-by: Jes Sorensen <jes@trained-monkey.org>
Cc: "Luck, Tony" <tony.luck@intel.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

1 files changed, 105 insertions, 95 deletions

diff --git a/arch/ia64/kernel/uncached.c b/arch/ia64/kernel/uncached.c
index fcd2bad0286f..5f03b9e524dd 100644
--- a/arch/ia64/kernel/uncached.c
+++ b/arch/ia64/kernel/uncached.c
@@ -1,5 +1,5 @@
 /*
- * Copyright (C) 2001-2005 Silicon Graphics, Inc.  All rights reserved.
+ * Copyright (C) 2001-2006 Silicon Graphics, Inc.  All rights reserved.
  *
  * This program is free software; you can redistribute it and/or modify it
  * under the terms of version 2 of the GNU General Public License
@@ -29,15 +29,8 @@
 #include <asm/tlbflush.h>
 #include <asm/sn/arch.h>
 
-#define DEBUG   0
 
-#if DEBUG
-#define dprintk                 printk
-#else
-#define dprintk(x...)           do { } while (0)
-#endif
-
-void __init efi_memmap_walk_uc (efi_freemem_callback_t callback);
+extern void __init efi_memmap_walk_uc(efi_freemem_callback_t, void *);
 
 #define MAX_UNCACHED_GRANULES   5
 static int allocated_granules;
@@ -60,6 +53,7 @@ static void uncached_ipi_visibility(void *data)
 static void uncached_ipi_mc_drain(void *data)
 {
         int status;
+
         status = ia64_pal_mc_drain();
         if (status)
                 printk(KERN_WARNING "ia64_pal_mc_drain() failed with %i on "
@@ -67,30 +61,35 @@ static void uncached_ipi_mc_drain(void *data)
 }
 
 
-static unsigned long
-uncached_get_new_chunk(struct gen_pool *poolp)
+/*
+ * Add a new chunk of uncached memory pages to the specified pool.
+ *
+ * @pool: pool to add new chunk of uncached memory to
+ * @nid: node id of node to allocate memory from, or -1
+ *
+ * This is accomplished by first allocating a granule of cached memory pages
+ * and then converting them to uncached memory pages.
+ */
+static int uncached_add_chunk(struct gen_pool *pool, int nid)
 {
         struct page *page;
-        void *tmp;
         int status, i;
-        unsigned long addr, node;
+        unsigned long c_addr, uc_addr;
 
         if (allocated_granules >= MAX_UNCACHED_GRANULES)
-                return 0;
+                return -1;
+
+        /* attempt to allocate a granule's worth of cached memory pages */
 
-        node = poolp->private;
-        page = alloc_pages_node(node, GFP_KERNEL | __GFP_ZERO,
+        page = alloc_pages_node(nid, GFP_KERNEL | __GFP_ZERO,
                                 IA64_GRANULE_SHIFT-PAGE_SHIFT);
+        if (!page)
+                return -1;
 
-        dprintk(KERN_INFO "get_new_chunk page %p, addr %lx\n",
-                page, (unsigned long)(page-vmem_map) << PAGE_SHIFT);
+        /* convert the memory pages from cached to uncached */
 
-        /*
-         * Do magic if no mem on local node! XXX
-         */
-        if (!page)
-                return 0;
-        tmp = page_address(page);
+        c_addr = (unsigned long)page_address(page);
+        uc_addr = c_addr - PAGE_OFFSET + __IA64_UNCACHED_OFFSET;
 
         /*
          * There's a small race here where it's possible for someone to
@@ -100,76 +99,90 @@ uncached_get_new_chunk(struct gen_pool *poolp)
         for (i = 0; i < (IA64_GRANULE_SIZE / PAGE_SIZE); i++)
                 SetPageUncached(&page[i]);
 
-        flush_tlb_kernel_range(tmp, tmp + IA64_GRANULE_SIZE);
+        flush_tlb_kernel_range(uc_addr, uc_adddr + IA64_GRANULE_SIZE);
 
         status = ia64_pal_prefetch_visibility(PAL_VISIBILITY_PHYSICAL);
-
-        dprintk(KERN_INFO "pal_prefetch_visibility() returns %i on cpu %i\n",
-                status, raw_smp_processor_id());
-
         if (!status) {
                 status = smp_call_function(uncached_ipi_visibility, NULL, 0, 1);
                 if (status)
-                        printk(KERN_WARNING "smp_call_function failed for "
-                               "uncached_ipi_visibility! (%i)\n", status);
+                        goto failed;
         }
 
+        preempt_disable();
+
         if (ia64_platform_is("sn2"))
-                sn_flush_all_caches((unsigned long)tmp, IA64_GRANULE_SIZE);
+                sn_flush_all_caches(uc_addr, IA64_GRANULE_SIZE);
         else
-                flush_icache_range((unsigned long)tmp,
-                                   (unsigned long)tmp+IA64_GRANULE_SIZE);
+                flush_icache_range(uc_addr, uc_addr + IA64_GRANULE_SIZE);
+
+        /* flush the just introduced uncached translation from the TLB */
+        local_flush_tlb_all();
+
+        preempt_enable();
 
         ia64_pal_mc_drain();
         status = smp_call_function(uncached_ipi_mc_drain, NULL, 0, 1);
         if (status)
-                printk(KERN_WARNING "smp_call_function failed for "
-                       "uncached_ipi_mc_drain! (%i)\n", status);
+                goto failed;
 
-        addr = (unsigned long)tmp - PAGE_OFFSET + __IA64_UNCACHED_OFFSET;
+        /*
+         * The chunk of memory pages has been converted to uncached so now we
+         * can add it to the pool.
+         */
+        status = gen_pool_add(pool, uc_addr, IA64_GRANULE_SIZE, nid);
+        if (status)
+                goto failed;
 
         allocated_granules++;
-        return addr;
+        return 0;
+
+        /* failed to convert or add the chunk so give it back to the kernel */
+failed:
+        for (i = 0; i < (IA64_GRANULE_SIZE / PAGE_SIZE); i++)
+                ClearPageUncached(&page[i]);
+
+        free_pages(c_addr, IA64_GRANULE_SHIFT-PAGE_SHIFT);
+        return -1;
 }
 
 
 /*
  * uncached_alloc_page
  *
+ * @starting_nid: node id of node to start with, or -1
+ *
  * Allocate 1 uncached page. Allocates on the requested node. If no
  * uncached pages are available on the requested node, roundrobin starting
- * with higher nodes.
+ * with the next higher node.
  */
-unsigned long
-uncached_alloc_page(int nid)
+unsigned long uncached_alloc_page(int starting_nid)
 {
-        unsigned long maddr;
+        unsigned long uc_addr;
+        struct gen_pool *pool;
+        int nid;
 
-        maddr = gen_pool_alloc(uncached_pool[nid], PAGE_SIZE);
+        if (unlikely(starting_nid >= MAX_NUMNODES))
+                return 0;
 
-        dprintk(KERN_DEBUG "uncached_alloc_page returns %lx on node %i\n",
-                maddr, nid);
+        if (starting_nid < 0)
+                starting_nid = numa_node_id();
+        nid = starting_nid;
 
-        /*
-         * If no memory is availble on our local node, try the
-         * remaining nodes in the system.
-         */
-        if (!maddr) {
-                int i;
-
-                for (i = MAX_NUMNODES - 1; i >= 0; i--) {
-                        if (i == nid || !node_online(i))
-                                continue;
-                        maddr = gen_pool_alloc(uncached_pool[i], PAGE_SIZE);
-                        dprintk(KERN_DEBUG "uncached_alloc_page alternate search "
-                                "returns %lx on node %i\n", maddr, i);
-                        if (maddr) {
-                                break;
-                        }
-                }
-        }
+        do {
+                if (!node_online(nid))
+                        continue;
+                pool = uncached_pool[nid];
+                if (pool == NULL)
+                        continue;
+                do {
+                        uc_addr = gen_pool_alloc(pool, PAGE_SIZE);
+                        if (uc_addr != 0)
+                                return uc_addr;
+                } while (uncached_add_chunk(pool, nid) == 0);
+
+        } while ((nid = (nid + 1) % MAX_NUMNODES) != starting_nid);
 
-        return maddr;
+        return 0;
 }
 EXPORT_SYMBOL(uncached_alloc_page);
 
@@ -177,21 +190,22 @@ EXPORT_SYMBOL(uncached_alloc_page);
 /*
  * uncached_free_page
  *
+ * @uc_addr: uncached address of page to free
+ *
  * Free a single uncached page.
  */
-void
-uncached_free_page(unsigned long maddr)
+void uncached_free_page(unsigned long uc_addr)
 {
-        int node;
-
-        node = paddr_to_nid(maddr - __IA64_UNCACHED_OFFSET);
+        int nid = paddr_to_nid(uc_addr - __IA64_UNCACHED_OFFSET);
+        struct gen_pool *pool = uncached_pool[nid];
 
-        dprintk(KERN_DEBUG "uncached_free_page(%lx) on node %i\n", maddr, node);
+        if (unlikely(pool == NULL))
+                return;
 
-        if ((maddr & (0XFUL << 60)) != __IA64_UNCACHED_OFFSET)
-                panic("uncached_free_page invalid address %lx\n", maddr);
+        if ((uc_addr & (0XFUL << 60)) != __IA64_UNCACHED_OFFSET)
+                panic("uncached_free_page invalid address %lx\n", uc_addr);
 
-        gen_pool_free(uncached_pool[node], maddr, PAGE_SIZE);
+        gen_pool_free(pool, uc_addr, PAGE_SIZE);
 }
 EXPORT_SYMBOL(uncached_free_page);
 
@@ -199,43 +213,39 @@ EXPORT_SYMBOL(uncached_free_page);
 /*
  * uncached_build_memmap,
  *
+ * @uc_start: uncached starting address of a chunk of uncached memory
+ * @uc_end: uncached ending address of a chunk of uncached memory
+ * @arg: ignored, (NULL argument passed in on call to efi_memmap_walk_uc())
+ *
  * Called at boot time to build a map of pages that can be used for
  * memory special operations.
  */
-static int __init
-uncached_build_memmap(unsigned long start, unsigned long end, void *arg)
+static int __init uncached_build_memmap(unsigned long uc_start,
+                                        unsigned long uc_end, void *arg)
 {
-        long length = end - start;
-        int node;
-
-        dprintk(KERN_ERR "uncached_build_memmap(%lx %lx)\n", start, end);
+        int nid = paddr_to_nid(uc_start - __IA64_UNCACHED_OFFSET);
+        struct gen_pool *pool = uncached_pool[nid];
+        size_t size = uc_end - uc_start;
 
         touch_softlockup_watchdog();
-        memset((char *)start, 0, length);
 
-        node = paddr_to_nid(start - __IA64_UNCACHED_OFFSET);
-
-        for (; start < end ; start += PAGE_SIZE) {
-                dprintk(KERN_INFO "sticking %lx into the pool!\n", start);
-                gen_pool_free(uncached_pool[node], start, PAGE_SIZE);
+        if (pool != NULL) {
+                memset((char *)uc_start, 0, size);
+                (void) gen_pool_add(pool, uc_start, size, nid);
         }
-
         return 0;
 }
 
 
-static int __init uncached_init(void) {
-        int i;
+static int __init uncached_init(void)
+{
+        int nid;
 
-        for (i = 0; i < MAX_NUMNODES; i++) {
-                if (!node_online(i))
-                        continue;
-                uncached_pool[i] = gen_pool_create(0, IA64_GRANULE_SHIFT,
-                                                   &uncached_get_new_chunk, i);
+        for_each_online_node(nid) {
+                uncached_pool[nid] = gen_pool_create(PAGE_SHIFT, nid);
         }
 
-        efi_memmap_walk_uc(uncached_build_memmap);
-
+        efi_memmap_walk_uc(uncached_build_memmap, NULL);
         return 0;
 }