2.4.13-pre5

 mm

diff -u --recursive --new-file v2.4.12/linux/mm/filemap.c linux/mm/filemap.c
--- v2.4.12/linux/mm/filemap.c   Tue Oct  9 17:06:53 2001
+++ linux/mm/filemap.c   Wed Oct 17 10:21:37 2001
@@ -667,8 +667,7 @@
 static int FASTCALL(page_cache_read(struct file * file, unsigned long offset));
 static int page_cache_read(struct file * file, unsigned long offset)
 {
-   struct inode *inode = file->f_dentry->d_inode;
-   struct address_space *mapping = inode->i_mapping;
+   struct address_space *mapping = file->f_dentry->d_inode->i_mapping;
    struct page **hash = page_hash(mapping, offset);
    struct page *page; 
 
@@ -1521,6 +1520,53 @@
    return retval;
 }
 
+static ssize_t do_readahead(struct file *file, unsigned long index, unsigned long nr)
+{
+   struct address_space *mapping = file->f_dentry->d_inode->i_mapping;
+   unsigned long max;
+
+   if (!mapping || !mapping->a_ops || !mapping->a_ops->readpage)
+      return -EINVAL;
+
+   /* Limit it to the size of the file.. */
+   max = (mapping->host->i_size + ~PAGE_CACHE_MASK) >> PAGE_CACHE_SHIFT;
+   if (index > max)
+      return 0;
+   max -= index;
+   if (nr > max)
+      nr = max;
+
+   /* And limit it to a sane percentage of the inactive list.. */
+   max = nr_inactive_pages / 2;
+   if (nr > max)
+      nr = max;
+
+   while (nr) {
+      page_cache_read(file, index);
+      index++;
+      nr--;
+   }
+   return 0;
+}
+
+asmlinkage ssize_t sys_readahead(int fd, loff_t offset, size_t count)
+{
+   ssize_t ret;
+   struct file *file;
+
+   ret = -EBADF;
+   file = fget(fd);
+   if (file) {
+      if (file->f_mode & FMODE_READ) {
+         unsigned long start = offset >> PAGE_CACHE_SHIFT;
+         unsigned long len = (count + ((long)offset & ~PAGE_CACHE_MASK)) >> PAGE_CACHE_SHIFT;
+         ret = do_readahead(file, start, len);
+      }
+      fput(file);
+   }
+   return ret;
+}
+
 /*
  * Read-ahead and flush behind for MADV_SEQUENTIAL areas.  Since we are
  * sure this is sequential access, we don't need a flexible read-ahead
@@ -1589,12 +1635,13 @@
 {
    int error;
    struct file *file = area->vm_file;
-   struct inode *inode = file->f_dentry->d_inode;
-   struct address_space *mapping = inode->i_mapping;
+   struct address_space *mapping = file->f_dentry->d_inode->i_mapping;
+   struct inode *inode = mapping->host;
    struct page *page, **hash, *old_page;
-   unsigned long size, pgoff;
+   unsigned long size, pgoff, endoff;
 
    pgoff = ((address - area->vm_start) >> PAGE_CACHE_SHIFT) + area->vm_pgoff;
+   endoff = ((area->vm_end - area->vm_start) >> PAGE_CACHE_SHIFT) + area->vm_pgoff;
 
 retry_all:
    /*
@@ -1605,6 +1652,10 @@
    if ((pgoff >= size) && (area->vm_mm == current->mm))
       return NULL;
 
+   /* The "size" of the file, as far as mmap is concerned, isn't bigger than the mapping */
+   if (size > endoff)
+      size = endoff;
+
    /*
     * Do we have something in the page cache already?
     */
@@ -1851,15 +1902,14 @@
 
 int generic_file_mmap(struct file * file, struct vm_area_struct * vma)
 {
-   struct inode *inode = file->f_dentry->d_inode;
+   struct address_space *mapping = file->f_dentry->d_inode->i_mapping;
+   struct inode *inode = mapping->host;
 
    if ((vma->vm_flags & VM_SHARED) && (vma->vm_flags & VM_MAYWRITE)) {
-      if (!inode->i_mapping->a_ops->writepage)
+      if (!mapping->a_ops->writepage)
          return -EINVAL;
    }
-   if (!inode->i_sb || !S_ISREG(inode->i_mode))
-      return -EACCES;
-   if (!inode->i_mapping->a_ops->readpage)
+   if (!mapping->a_ops->readpage)
       return -ENOEXEC;
    UPDATE_ATIME(inode);
    vma->vm_ops = &generic_file_vm_ops;
@@ -2309,7 +2359,7 @@
    unsigned long pgoff)
 {
    unsigned char present = 0;
-   struct address_space * as = &vma->vm_file->f_dentry->d_inode->i_data;
+   struct address_space * as = vma->vm_file->f_dentry->d_inode->i_mapping;
    struct page * page, ** hash = page_hash(as, pgoff);
 
    spin_lock(&pagecache_lock);