1 files changed, 17 insertions, 108 deletions

diff --git a/drivers/char/mem.c b/drivers/char/mem.c
index bbee97ff355f..64551ab6be03 100644
--- a/drivers/char/mem.c
+++ b/drivers/char/mem.c
@@ -625,65 +625,10 @@ static ssize_t splice_write_null(struct pipe_inode_info *pipe,struct file *out,
         return splice_from_pipe(pipe, out, ppos, len, flags, pipe_to_null);
 }
 
-#ifdef CONFIG_MMU
-/*
- * For fun, we are using the MMU for this.
- */
-static inline size_t read_zero_pagealigned(char __user * buf, size_t size)
-{
-        struct mm_struct *mm;
-        struct vm_area_struct * vma;
-        unsigned long addr=(unsigned long)buf;
-
-        mm = current->mm;
-        /* Oops, this was forgotten before. -ben */
-        down_read(&mm->mmap_sem);
-
-        /* For private mappings, just map in zero pages. */
-        for (vma = find_vma(mm, addr); vma; vma = vma->vm_next) {
-                unsigned long count;
-
-                if (vma->vm_start > addr || (vma->vm_flags & VM_WRITE) == 0)
-                        goto out_up;
-                if (vma->vm_flags & (VM_SHARED | VM_HUGETLB))
-                        break;
-                count = vma->vm_end - addr;
-                if (count > size)
-                        count = size;
-
-                zap_page_range(vma, addr, count, NULL);
-                if (zeromap_page_range(vma, addr, count, PAGE_COPY))
-                        break;
-
-                size -= count;
-                buf += count;
-                addr += count;
-                if (size == 0)
-                        goto out_up;
-        }
-
-        up_read(&mm->mmap_sem);
-        
-        /* The shared case is hard. Let's do the conventional zeroing. */ 
-        do {
-                unsigned long unwritten = clear_user(buf, PAGE_SIZE);
-                if (unwritten)
-                        return size + unwritten - PAGE_SIZE;
-                cond_resched();
-                buf += PAGE_SIZE;
-                size -= PAGE_SIZE;
-        } while (size);
-
-        return size;
-out_up:
-        up_read(&mm->mmap_sem);
-        return size;
-}
-
 static ssize_t read_zero(struct file * file, char __user * buf, 
                          size_t count, loff_t *ppos)
 {
-        unsigned long left, unwritten, written = 0;
+        size_t written;
 
         if (!count)
                 return 0;
@@ -691,69 +636,33 @@ static ssize_t read_zero(struct file * file, char __user * buf,
         if (!access_ok(VERIFY_WRITE, buf, count))
                 return -EFAULT;
 
-        left = count;
-
-        /* do we want to be clever? Arbitrary cut-off */
-        if (count >= PAGE_SIZE*4) {
-                unsigned long partial;
+        written = 0;
+        while (count) {
+                unsigned long unwritten;
+                size_t chunk = count;
 
-                /* How much left of the page? */
-                partial = (PAGE_SIZE-1) & -(unsigned long) buf;
-                unwritten = clear_user(buf, partial);
-                written = partial - unwritten;
-                if (unwritten)
-                        goto out;
-                left -= partial;
-                buf += partial;
-                unwritten = read_zero_pagealigned(buf, left & PAGE_MASK);
-                written += (left & PAGE_MASK) - unwritten;
+                if (chunk > PAGE_SIZE)
+                        chunk = PAGE_SIZE;      /* Just for latency reasons */
+                unwritten = clear_user(buf, chunk);
+                written += chunk - unwritten;
                 if (unwritten)
-                        goto out;
-                buf += left & PAGE_MASK;
-                left &= ~PAGE_MASK;
-        }
-        unwritten = clear_user(buf, left);
-        written += left - unwritten;
-out:
-        return written ? written : -EFAULT;
-}
-
-static int mmap_zero(struct file * file, struct vm_area_struct * vma)
-{
-        int err;
-
-        if (vma->vm_flags & VM_SHARED)
-                return shmem_zero_setup(vma);
-        err = zeromap_page_range(vma, vma->vm_start,
-                        vma->vm_end - vma->vm_start, vma->vm_page_prot);
-        BUG_ON(err == -EEXIST);
-        return err;
-}
-#else /* CONFIG_MMU */
-static ssize_t read_zero(struct file * file, char * buf, 
-                         size_t count, loff_t *ppos)
-{
-        size_t todo = count;
-
-        while (todo) {
-                size_t chunk = todo;
-
-                if (chunk > 4096)
-                        chunk = 4096;   /* Just for latency reasons */
-                if (clear_user(buf, chunk))
-                        return -EFAULT;
+                        break;
                 buf += chunk;
-                todo -= chunk;
+                count -= chunk;
                 cond_resched();
         }
-        return count;
+        return written ? written : -EFAULT;
 }
 
 static int mmap_zero(struct file * file, struct vm_area_struct * vma)
 {
+#ifndef CONFIG_MMU
         return -ENOSYS;
+#endif
+        if (vma->vm_flags & VM_SHARED)
+                return shmem_zero_setup(vma);
+        return 0;
 }
-#endif /* CONFIG_MMU */
 
 static ssize_t write_full(struct file * file, const char __user * buf,
                           size_t count, loff_t *ppos)