ALSA: usb-audio: add support for Akai MPD16
[safe/jmp/linux-2.6] / mm / vmalloc.c
index 204b824..ae00746 100644 (file)
@@ -12,6 +12,7 @@
 #include <linux/mm.h>
 #include <linux/module.h>
 #include <linux/highmem.h>
+#include <linux/sched.h>
 #include <linux/slab.h>
 #include <linux/spinlock.h>
 #include <linux/interrupt.h>
 #include <linux/rcupdate.h>
 #include <linux/pfn.h>
 #include <linux/kmemleak.h>
-
 #include <asm/atomic.h>
 #include <asm/uaccess.h>
 #include <asm/tlbflush.h>
+#include <asm/shmparam.h>
 
 
 /*** Page table manipulation functions ***/
@@ -168,11 +169,9 @@ static int vmap_page_range_noflush(unsigned long start, unsigned long end,
                next = pgd_addr_end(addr, end);
                err = vmap_pud_range(pgd, addr, next, prot, pages, &nr);
                if (err)
-                       break;
+                       return err;
        } while (pgd++, addr = next, addr != end);
 
-       if (unlikely(err))
-               return err;
        return nr;
 }
 
@@ -186,7 +185,7 @@ static int vmap_page_range(unsigned long start, unsigned long end,
        return ret;
 }
 
-static inline int is_vmalloc_or_module_addr(const void *x)
+int is_vmalloc_or_module_addr(const void *x)
 {
        /*
         * ARM, x86-64 and sparc64 put modules in a special place,
@@ -510,6 +509,9 @@ static unsigned long lazy_max_pages(void)
 
 static atomic_t vmap_lazy_nr = ATOMIC_INIT(0);
 
+/* for per-CPU blocks */
+static void purge_fragmented_blocks_allcpus(void);
+
 /*
  * Purges all lazily-freed vmap areas.
  *
@@ -540,6 +542,9 @@ static void __purge_vmap_area_lazy(unsigned long *start, unsigned long *end,
        } else
                spin_lock(&purge_lock);
 
+       if (sync)
+               purge_fragmented_blocks_allcpus();
+
        rcu_read_lock();
        list_for_each_entry_rcu(va, &vmap_area_list, list) {
                if (va->flags & VM_LAZY_FREE) {
@@ -556,10 +561,8 @@ static void __purge_vmap_area_lazy(unsigned long *start, unsigned long *end,
        }
        rcu_read_unlock();
 
-       if (nr) {
-               BUG_ON(nr > atomic_read(&vmap_lazy_nr));
+       if (nr)
                atomic_sub(nr, &vmap_lazy_nr);
-       }
 
        if (nr || force_flush)
                flush_tlb_kernel_range(*start, *end);
@@ -670,8 +673,6 @@ static bool vmap_initialized __read_mostly = false;
 struct vmap_block_queue {
        spinlock_t lock;
        struct list_head free;
-       struct list_head dirty;
-       unsigned int nr_dirty;
 };
 
 struct vmap_block {
@@ -681,10 +682,9 @@ struct vmap_block {
        unsigned long free, dirty;
        DECLARE_BITMAP(alloc_map, VMAP_BBMAP_BITS);
        DECLARE_BITMAP(dirty_map, VMAP_BBMAP_BITS);
-       union {
-               struct list_head free_list;
-               struct rcu_head rcu_head;
-       };
+       struct list_head free_list;
+       struct rcu_head rcu_head;
+       struct list_head purge;
 };
 
 /* Queue of free and dirty vmap blocks, for allocation and flushing purposes */
@@ -760,9 +760,9 @@ static struct vmap_block *new_vmap_block(gfp_t gfp_mask)
        vbq = &get_cpu_var(vmap_block_queue);
        vb->vbq = vbq;
        spin_lock(&vbq->lock);
-       list_add(&vb->free_list, &vbq->free);
+       list_add_rcu(&vb->free_list, &vbq->free);
        spin_unlock(&vbq->lock);
-       put_cpu_var(vmap_cpu_blocks);
+       put_cpu_var(vmap_block_queue);
 
        return vb;
 }
@@ -779,8 +779,6 @@ static void free_vmap_block(struct vmap_block *vb)
        struct vmap_block *tmp;
        unsigned long vb_idx;
 
-       BUG_ON(!list_empty(&vb->free_list));
-
        vb_idx = addr_to_vb_idx(vb->va->va_start);
        spin_lock(&vmap_block_tree_lock);
        tmp = radix_tree_delete(&vmap_block_tree, vb_idx);
@@ -791,12 +789,61 @@ static void free_vmap_block(struct vmap_block *vb)
        call_rcu(&vb->rcu_head, rcu_free_vb);
 }
 
+static void purge_fragmented_blocks(int cpu)
+{
+       LIST_HEAD(purge);
+       struct vmap_block *vb;
+       struct vmap_block *n_vb;
+       struct vmap_block_queue *vbq = &per_cpu(vmap_block_queue, cpu);
+
+       rcu_read_lock();
+       list_for_each_entry_rcu(vb, &vbq->free, free_list) {
+
+               if (!(vb->free + vb->dirty == VMAP_BBMAP_BITS && vb->dirty != VMAP_BBMAP_BITS))
+                       continue;
+
+               spin_lock(&vb->lock);
+               if (vb->free + vb->dirty == VMAP_BBMAP_BITS && vb->dirty != VMAP_BBMAP_BITS) {
+                       vb->free = 0; /* prevent further allocs after releasing lock */
+                       vb->dirty = VMAP_BBMAP_BITS; /* prevent purging it again */
+                       bitmap_fill(vb->alloc_map, VMAP_BBMAP_BITS);
+                       bitmap_fill(vb->dirty_map, VMAP_BBMAP_BITS);
+                       spin_lock(&vbq->lock);
+                       list_del_rcu(&vb->free_list);
+                       spin_unlock(&vbq->lock);
+                       spin_unlock(&vb->lock);
+                       list_add_tail(&vb->purge, &purge);
+               } else
+                       spin_unlock(&vb->lock);
+       }
+       rcu_read_unlock();
+
+       list_for_each_entry_safe(vb, n_vb, &purge, purge) {
+               list_del(&vb->purge);
+               free_vmap_block(vb);
+       }
+}
+
+static void purge_fragmented_blocks_thiscpu(void)
+{
+       purge_fragmented_blocks(smp_processor_id());
+}
+
+static void purge_fragmented_blocks_allcpus(void)
+{
+       int cpu;
+
+       for_each_possible_cpu(cpu)
+               purge_fragmented_blocks(cpu);
+}
+
 static void *vb_alloc(unsigned long size, gfp_t gfp_mask)
 {
        struct vmap_block_queue *vbq;
        struct vmap_block *vb;
        unsigned long addr = 0;
        unsigned int order;
+       int purge = 0;
 
        BUG_ON(size & ~PAGE_MASK);
        BUG_ON(size > PAGE_SIZE*VMAP_MAX_ALLOC);
@@ -809,25 +856,39 @@ again:
                int i;
 
                spin_lock(&vb->lock);
+               if (vb->free < 1UL << order)
+                       goto next;
+
                i = bitmap_find_free_region(vb->alloc_map,
                                                VMAP_BBMAP_BITS, order);
 
-               if (i >= 0) {
-                       addr = vb->va->va_start + (i << PAGE_SHIFT);
-                       BUG_ON(addr_to_vb_idx(addr) !=
-                                       addr_to_vb_idx(vb->va->va_start));
-                       vb->free -= 1UL << order;
-                       if (vb->free == 0) {
-                               spin_lock(&vbq->lock);
-                               list_del_init(&vb->free_list);
-                               spin_unlock(&vbq->lock);
+               if (i < 0) {
+                       if (vb->free + vb->dirty == VMAP_BBMAP_BITS) {
+                               /* fragmented and no outstanding allocations */
+                               BUG_ON(vb->dirty != VMAP_BBMAP_BITS);
+                               purge = 1;
                        }
-                       spin_unlock(&vb->lock);
-                       break;
+                       goto next;
                }
+               addr = vb->va->va_start + (i << PAGE_SHIFT);
+               BUG_ON(addr_to_vb_idx(addr) !=
+                               addr_to_vb_idx(vb->va->va_start));
+               vb->free -= 1UL << order;
+               if (vb->free == 0) {
+                       spin_lock(&vbq->lock);
+                       list_del_rcu(&vb->free_list);
+                       spin_unlock(&vbq->lock);
+               }
+               spin_unlock(&vb->lock);
+               break;
+next:
                spin_unlock(&vb->lock);
        }
-       put_cpu_var(vmap_cpu_blocks);
+
+       if (purge)
+               purge_fragmented_blocks_thiscpu();
+
+       put_cpu_var(vmap_block_queue);
        rcu_read_unlock();
 
        if (!addr) {
@@ -863,11 +924,11 @@ static void vb_free(const void *addr, unsigned long size)
        BUG_ON(!vb);
 
        spin_lock(&vb->lock);
-       bitmap_allocate_region(vb->dirty_map, offset >> PAGE_SHIFT, order);
+       BUG_ON(bitmap_allocate_region(vb->dirty_map, offset >> PAGE_SHIFT, order));
 
        vb->dirty += 1UL << order;
        if (vb->dirty == VMAP_BBMAP_BITS) {
-               BUG_ON(vb->free || !list_empty(&vb->free_list));
+               BUG_ON(vb->free);
                spin_unlock(&vb->lock);
                free_vmap_block(vb);
        } else
@@ -1036,8 +1097,6 @@ void __init vmalloc_init(void)
                vbq = &per_cpu(vmap_block_queue, i);
                spin_lock_init(&vbq->lock);
                INIT_LIST_HEAD(&vbq->free);
-               INIT_LIST_HEAD(&vbq->dirty);
-               vbq->nr_dirty = 0;
        }
 
        /* Import existing vmlist entries. */
@@ -1158,12 +1217,11 @@ static void insert_vmalloc_vm(struct vm_struct *vm, struct vmap_area *va,
 }
 
 static struct vm_struct *__get_vm_area_node(unsigned long size,
-               unsigned long flags, unsigned long start, unsigned long end,
-               int node, gfp_t gfp_mask, void *caller)
+               unsigned long align, unsigned long flags, unsigned long start,
+               unsigned long end, int node, gfp_t gfp_mask, void *caller)
 {
        static struct vmap_area *va;
        struct vm_struct *area;
-       unsigned long align = 1;
 
        BUG_ON(in_interrupt());
        if (flags & VM_IOREMAP) {
@@ -1203,7 +1261,7 @@ static struct vm_struct *__get_vm_area_node(unsigned long size,
 struct vm_struct *__get_vm_area(unsigned long size, unsigned long flags,
                                unsigned long start, unsigned long end)
 {
-       return __get_vm_area_node(size, flags, start, end, -1, GFP_KERNEL,
+       return __get_vm_area_node(size, 1, flags, start, end, -1, GFP_KERNEL,
                                                __builtin_return_address(0));
 }
 EXPORT_SYMBOL_GPL(__get_vm_area);
@@ -1212,7 +1270,7 @@ struct vm_struct *__get_vm_area_caller(unsigned long size, unsigned long flags,
                                       unsigned long start, unsigned long end,
                                       void *caller)
 {
-       return __get_vm_area_node(size, flags, start, end, -1, GFP_KERNEL,
+       return __get_vm_area_node(size, 1, flags, start, end, -1, GFP_KERNEL,
                                  caller);
 }
 
@@ -1227,22 +1285,22 @@ struct vm_struct *__get_vm_area_caller(unsigned long size, unsigned long flags,
  */
 struct vm_struct *get_vm_area(unsigned long size, unsigned long flags)
 {
-       return __get_vm_area_node(size, flags, VMALLOC_START, VMALLOC_END,
+       return __get_vm_area_node(size, 1, flags, VMALLOC_START, VMALLOC_END,
                                -1, GFP_KERNEL, __builtin_return_address(0));
 }
 
 struct vm_struct *get_vm_area_caller(unsigned long size, unsigned long flags,
                                void *caller)
 {
-       return __get_vm_area_node(size, flags, VMALLOC_START, VMALLOC_END,
+       return __get_vm_area_node(size, 1, flags, VMALLOC_START, VMALLOC_END,
                                                -1, GFP_KERNEL, caller);
 }
 
 struct vm_struct *get_vm_area_node(unsigned long size, unsigned long flags,
                                   int node, gfp_t gfp_mask)
 {
-       return __get_vm_area_node(size, flags, VMALLOC_START, VMALLOC_END, node,
-                                 gfp_mask, __builtin_return_address(0));
+       return __get_vm_area_node(size, 1, flags, VMALLOC_START, VMALLOC_END,
+                                 node, gfp_mask, __builtin_return_address(0));
 }
 
 static struct vm_struct *find_vm_area(const void *addr)
@@ -1272,17 +1330,21 @@ struct vm_struct *remove_vm_area(const void *addr)
        if (va && va->flags & VM_VM_AREA) {
                struct vm_struct *vm = va->private;
                struct vm_struct *tmp, **p;
-
-               vmap_debug_free_range(va->va_start, va->va_end);
-               free_unmap_vmap_area(va);
-               vm->size -= PAGE_SIZE;
-
+               /*
+                * remove from list and disallow access to this vm_struct
+                * before unmap. (address range confliction is maintained by
+                * vmap.)
+                */
                write_lock(&vmlist_lock);
                for (p = &vmlist; (tmp = *p) != vm; p = &tmp->next)
                        ;
                *p = tmp->next;
                write_unlock(&vmlist_lock);
 
+               vmap_debug_free_range(va->va_start, va->va_end);
+               free_unmap_vmap_area(va);
+               vm->size -= PAGE_SIZE;
+
                return vm;
        }
        return NULL;
@@ -1384,7 +1446,7 @@ void *vmap(struct page **pages, unsigned int count,
 
        might_sleep();
 
-       if (count > num_physpages)
+       if (count > totalram_pages)
                return NULL;
 
        area = get_vm_area_caller((count << PAGE_SHIFT), flags,
@@ -1401,13 +1463,15 @@ void *vmap(struct page **pages, unsigned int count,
 }
 EXPORT_SYMBOL(vmap);
 
-static void *__vmalloc_node(unsigned long size, gfp_t gfp_mask, pgprot_t prot,
+static void *__vmalloc_node(unsigned long size, unsigned long align,
+                           gfp_t gfp_mask, pgprot_t prot,
                            int node, void *caller);
 static void *__vmalloc_area_node(struct vm_struct *area, gfp_t gfp_mask,
                                 pgprot_t prot, int node, void *caller)
 {
        struct page **pages;
        unsigned int nr_pages, array_size, i;
+       gfp_t nested_gfp = (gfp_mask & GFP_RECLAIM_MASK) | __GFP_ZERO;
 
        nr_pages = (area->size - PAGE_SIZE) >> PAGE_SHIFT;
        array_size = (nr_pages * sizeof(struct page *));
@@ -1415,13 +1479,11 @@ static void *__vmalloc_area_node(struct vm_struct *area, gfp_t gfp_mask,
        area->nr_pages = nr_pages;
        /* Please note that the recursion is strictly bounded. */
        if (array_size > PAGE_SIZE) {
-               pages = __vmalloc_node(array_size, gfp_mask | __GFP_ZERO,
+               pages = __vmalloc_node(array_size, 1, nested_gfp|__GFP_HIGHMEM,
                                PAGE_KERNEL, node, caller);
                area->flags |= VM_VPAGES;
        } else {
-               pages = kmalloc_node(array_size,
-                               (gfp_mask & GFP_RECLAIM_MASK) | __GFP_ZERO,
-                               node);
+               pages = kmalloc_node(array_size, nested_gfp, node);
        }
        area->pages = pages;
        area->caller = caller;
@@ -1474,6 +1536,7 @@ void *__vmalloc_area(struct vm_struct *area, gfp_t gfp_mask, pgprot_t prot)
 /**
  *     __vmalloc_node  -  allocate virtually contiguous memory
  *     @size:          allocation size
+ *     @align:         desired alignment
  *     @gfp_mask:      flags for the page level allocator
  *     @prot:          protection mask for the allocated pages
  *     @node:          node to use for allocation or -1
@@ -1483,19 +1546,20 @@ void *__vmalloc_area(struct vm_struct *area, gfp_t gfp_mask, pgprot_t prot)
  *     allocator with @gfp_mask flags.  Map them into contiguous
  *     kernel virtual space, using a pagetable protection of @prot.
  */
-static void *__vmalloc_node(unsigned long size, gfp_t gfp_mask, pgprot_t prot,
-                                               int node, void *caller)
+static void *__vmalloc_node(unsigned long size, unsigned long align,
+                           gfp_t gfp_mask, pgprot_t prot,
+                           int node, void *caller)
 {
        struct vm_struct *area;
        void *addr;
        unsigned long real_size = size;
 
        size = PAGE_ALIGN(size);
-       if (!size || (size >> PAGE_SHIFT) > num_physpages)
+       if (!size || (size >> PAGE_SHIFT) > totalram_pages)
                return NULL;
 
-       area = __get_vm_area_node(size, VM_ALLOC, VMALLOC_START, VMALLOC_END,
-                                               node, gfp_mask, caller);
+       area = __get_vm_area_node(size, align, VM_ALLOC, VMALLOC_START,
+                                 VMALLOC_END, node, gfp_mask, caller);
 
        if (!area)
                return NULL;
@@ -1514,7 +1578,7 @@ static void *__vmalloc_node(unsigned long size, gfp_t gfp_mask, pgprot_t prot,
 
 void *__vmalloc(unsigned long size, gfp_t gfp_mask, pgprot_t prot)
 {
-       return __vmalloc_node(size, gfp_mask, prot, -1,
+       return __vmalloc_node(size, 1, gfp_mask, prot, -1,
                                __builtin_return_address(0));
 }
 EXPORT_SYMBOL(__vmalloc);
@@ -1530,7 +1594,7 @@ EXPORT_SYMBOL(__vmalloc);
  */
 void *vmalloc(unsigned long size)
 {
-       return __vmalloc_node(size, GFP_KERNEL | __GFP_HIGHMEM, PAGE_KERNEL,
+       return __vmalloc_node(size, 1, GFP_KERNEL | __GFP_HIGHMEM, PAGE_KERNEL,
                                        -1, __builtin_return_address(0));
 }
 EXPORT_SYMBOL(vmalloc);
@@ -1547,7 +1611,8 @@ void *vmalloc_user(unsigned long size)
        struct vm_struct *area;
        void *ret;
 
-       ret = __vmalloc_node(size, GFP_KERNEL | __GFP_HIGHMEM | __GFP_ZERO,
+       ret = __vmalloc_node(size, SHMLBA,
+                            GFP_KERNEL | __GFP_HIGHMEM | __GFP_ZERO,
                             PAGE_KERNEL, -1, __builtin_return_address(0));
        if (ret) {
                area = find_vm_area(ret);
@@ -1570,7 +1635,7 @@ EXPORT_SYMBOL(vmalloc_user);
  */
 void *vmalloc_node(unsigned long size, int node)
 {
-       return __vmalloc_node(size, GFP_KERNEL | __GFP_HIGHMEM, PAGE_KERNEL,
+       return __vmalloc_node(size, 1, GFP_KERNEL | __GFP_HIGHMEM, PAGE_KERNEL,
                                        node, __builtin_return_address(0));
 }
 EXPORT_SYMBOL(vmalloc_node);
@@ -1593,7 +1658,7 @@ EXPORT_SYMBOL(vmalloc_node);
 
 void *vmalloc_exec(unsigned long size)
 {
-       return __vmalloc_node(size, GFP_KERNEL | __GFP_HIGHMEM, PAGE_KERNEL_EXEC,
+       return __vmalloc_node(size, 1, GFP_KERNEL | __GFP_HIGHMEM, PAGE_KERNEL_EXEC,
                              -1, __builtin_return_address(0));
 }
 
@@ -1614,7 +1679,7 @@ void *vmalloc_exec(unsigned long size)
  */
 void *vmalloc_32(unsigned long size)
 {
-       return __vmalloc_node(size, GFP_VMALLOC32, PAGE_KERNEL,
+       return __vmalloc_node(size, 1, GFP_VMALLOC32, PAGE_KERNEL,
                              -1, __builtin_return_address(0));
 }
 EXPORT_SYMBOL(vmalloc_32);
@@ -1631,7 +1696,7 @@ void *vmalloc_32_user(unsigned long size)
        struct vm_struct *area;
        void *ret;
 
-       ret = __vmalloc_node(size, GFP_VMALLOC32 | __GFP_ZERO, PAGE_KERNEL,
+       ret = __vmalloc_node(size, 1, GFP_VMALLOC32 | __GFP_ZERO, PAGE_KERNEL,
                             -1, __builtin_return_address(0));
        if (ret) {
                area = find_vm_area(ret);
@@ -1641,10 +1706,120 @@ void *vmalloc_32_user(unsigned long size)
 }
 EXPORT_SYMBOL(vmalloc_32_user);
 
+/*
+ * small helper routine , copy contents to buf from addr.
+ * If the page is not present, fill zero.
+ */
+
+static int aligned_vread(char *buf, char *addr, unsigned long count)
+{
+       struct page *p;
+       int copied = 0;
+
+       while (count) {
+               unsigned long offset, length;
+
+               offset = (unsigned long)addr & ~PAGE_MASK;
+               length = PAGE_SIZE - offset;
+               if (length > count)
+                       length = count;
+               p = vmalloc_to_page(addr);
+               /*
+                * To do safe access to this _mapped_ area, we need
+                * lock. But adding lock here means that we need to add
+                * overhead of vmalloc()/vfree() calles for this _debug_
+                * interface, rarely used. Instead of that, we'll use
+                * kmap() and get small overhead in this access function.
+                */
+               if (p) {
+                       /*
+                        * we can expect USER0 is not used (see vread/vwrite's
+                        * function description)
+                        */
+                       void *map = kmap_atomic(p, KM_USER0);
+                       memcpy(buf, map + offset, length);
+                       kunmap_atomic(map, KM_USER0);
+               } else
+                       memset(buf, 0, length);
+
+               addr += length;
+               buf += length;
+               copied += length;
+               count -= length;
+       }
+       return copied;
+}
+
+static int aligned_vwrite(char *buf, char *addr, unsigned long count)
+{
+       struct page *p;
+       int copied = 0;
+
+       while (count) {
+               unsigned long offset, length;
+
+               offset = (unsigned long)addr & ~PAGE_MASK;
+               length = PAGE_SIZE - offset;
+               if (length > count)
+                       length = count;
+               p = vmalloc_to_page(addr);
+               /*
+                * To do safe access to this _mapped_ area, we need
+                * lock. But adding lock here means that we need to add
+                * overhead of vmalloc()/vfree() calles for this _debug_
+                * interface, rarely used. Instead of that, we'll use
+                * kmap() and get small overhead in this access function.
+                */
+               if (p) {
+                       /*
+                        * we can expect USER0 is not used (see vread/vwrite's
+                        * function description)
+                        */
+                       void *map = kmap_atomic(p, KM_USER0);
+                       memcpy(map + offset, buf, length);
+                       kunmap_atomic(map, KM_USER0);
+               }
+               addr += length;
+               buf += length;
+               copied += length;
+               count -= length;
+       }
+       return copied;
+}
+
+/**
+ *     vread() -  read vmalloc area in a safe way.
+ *     @buf:           buffer for reading data
+ *     @addr:          vm address.
+ *     @count:         number of bytes to be read.
+ *
+ *     Returns # of bytes which addr and buf should be increased.
+ *     (same number to @count). Returns 0 if [addr...addr+count) doesn't
+ *     includes any intersect with alive vmalloc area.
+ *
+ *     This function checks that addr is a valid vmalloc'ed area, and
+ *     copy data from that area to a given buffer. If the given memory range
+ *     of [addr...addr+count) includes some valid address, data is copied to
+ *     proper area of @buf. If there are memory holes, they'll be zero-filled.
+ *     IOREMAP area is treated as memory hole and no copy is done.
+ *
+ *     If [addr...addr+count) doesn't includes any intersects with alive
+ *     vm_struct area, returns 0.
+ *     @buf should be kernel's buffer. Because this function uses KM_USER0,
+ *     the caller should guarantee KM_USER0 is not used.
+ *
+ *     Note: In usual ops, vread() is never necessary because the caller
+ *     should know vmalloc() area is valid and can use memcpy().
+ *     This is for routines which have to access vmalloc area without
+ *     any informaion, as /dev/kmem.
+ *
+ */
+
 long vread(char *buf, char *addr, unsigned long count)
 {
        struct vm_struct *tmp;
        char *vaddr, *buf_start = buf;
+       unsigned long buflen = count;
        unsigned long n;
 
        /* Don't allow overflow */
@@ -1652,7 +1827,7 @@ long vread(char *buf, char *addr, unsigned long count)
                count = -(unsigned long) addr;
 
        read_lock(&vmlist_lock);
-       for (tmp = vmlist; tmp; tmp = tmp->next) {
+       for (tmp = vmlist; count && tmp; tmp = tmp->next) {
                vaddr = (char *) tmp->addr;
                if (addr >= vaddr + tmp->size - PAGE_SIZE)
                        continue;
@@ -1665,32 +1840,72 @@ long vread(char *buf, char *addr, unsigned long count)
                        count--;
                }
                n = vaddr + tmp->size - PAGE_SIZE - addr;
-               do {
-                       if (count == 0)
-                               goto finished;
-                       *buf = *addr;
-                       buf++;
-                       addr++;
-                       count--;
-               } while (--n > 0);
+               if (n > count)
+                       n = count;
+               if (!(tmp->flags & VM_IOREMAP))
+                       aligned_vread(buf, addr, n);
+               else /* IOREMAP area is treated as memory hole */
+                       memset(buf, 0, n);
+               buf += n;
+               addr += n;
+               count -= n;
        }
 finished:
        read_unlock(&vmlist_lock);
-       return buf - buf_start;
+
+       if (buf == buf_start)
+               return 0;
+       /* zero-fill memory holes */
+       if (buf != buf_start + buflen)
+               memset(buf, 0, buflen - (buf - buf_start));
+
+       return buflen;
 }
 
+/**
+ *     vwrite() -  write vmalloc area in a safe way.
+ *     @buf:           buffer for source data
+ *     @addr:          vm address.
+ *     @count:         number of bytes to be read.
+ *
+ *     Returns # of bytes which addr and buf should be incresed.
+ *     (same number to @count).
+ *     If [addr...addr+count) doesn't includes any intersect with valid
+ *     vmalloc area, returns 0.
+ *
+ *     This function checks that addr is a valid vmalloc'ed area, and
+ *     copy data from a buffer to the given addr. If specified range of
+ *     [addr...addr+count) includes some valid address, data is copied from
+ *     proper area of @buf. If there are memory holes, no copy to hole.
+ *     IOREMAP area is treated as memory hole and no copy is done.
+ *
+ *     If [addr...addr+count) doesn't includes any intersects with alive
+ *     vm_struct area, returns 0.
+ *     @buf should be kernel's buffer. Because this function uses KM_USER0,
+ *     the caller should guarantee KM_USER0 is not used.
+ *
+ *     Note: In usual ops, vwrite() is never necessary because the caller
+ *     should know vmalloc() area is valid and can use memcpy().
+ *     This is for routines which have to access vmalloc area without
+ *     any informaion, as /dev/kmem.
+ *
+ *     The caller should guarantee KM_USER1 is not used.
+ */
+
 long vwrite(char *buf, char *addr, unsigned long count)
 {
        struct vm_struct *tmp;
-       char *vaddr, *buf_start = buf;
-       unsigned long n;
+       char *vaddr;
+       unsigned long n, buflen;
+       int copied = 0;
 
        /* Don't allow overflow */
        if ((unsigned long) addr + count < count)
                count = -(unsigned long) addr;
+       buflen = count;
 
        read_lock(&vmlist_lock);
-       for (tmp = vmlist; tmp; tmp = tmp->next) {
+       for (tmp = vmlist; count && tmp; tmp = tmp->next) {
                vaddr = (char *) tmp->addr;
                if (addr >= vaddr + tmp->size - PAGE_SIZE)
                        continue;
@@ -1702,18 +1917,21 @@ long vwrite(char *buf, char *addr, unsigned long count)
                        count--;
                }
                n = vaddr + tmp->size - PAGE_SIZE - addr;
-               do {
-                       if (count == 0)
-                               goto finished;
-                       *addr = *buf;
-                       buf++;
-                       addr++;
-                       count--;
-               } while (--n > 0);
+               if (n > count)
+                       n = count;
+               if (!(tmp->flags & VM_IOREMAP)) {
+                       aligned_vwrite(buf, addr, n);
+                       copied++;
+               }
+               buf += n;
+               addr += n;
+               count -= n;
        }
 finished:
        read_unlock(&vmlist_lock);
-       return buf - buf_start;
+       if (!copied)
+               return 0;
+       return buflen;
 }
 
 /**