kanoj-mm18-2.3.22 incremental swapout() interface cleanup

@@ -106,7 +106,7 @@
 	unsigned long (*nopage)(struct vm_area_struct * area, unsigned long address, int write_access);
 	unsigned long (*wppage)(struct vm_area_struct * area, unsigned long address,
 		unsigned long page);
-	int (*swapout)(struct vm_area_struct *, struct page *);
+	int (*swapout)(struct page *, struct file *);
 };
 
 /*

@@ -33,7 +33,7 @@
 static void shm_open (struct vm_area_struct *shmd);
 static void shm_close (struct vm_area_struct *shmd);
 static unsigned long shm_nopage(struct vm_area_struct *, unsigned long, int);
-static int shm_swapout(struct vm_area_struct *, struct page *);
+static int shm_swapout(struct page *, struct file *);
 #ifdef CONFIG_PROC_FS
 static int sysvipc_shm_read_proc(char *buffer, char **start, off_t offset, int length, int *eof, void *data);
 #endif

@@ -660,7 +660,7 @@
  * data structures already, and shm_swap_out() will just
  * work off them..
  */
-static int shm_swapout(struct vm_area_struct * vma, struct page * page)
+static int shm_swapout(struct page * page, struct file *file)
 {
 	return 0;
 }

@@ -1447,27 +1447,25 @@
 	return retval;
 }
 
-static int filemap_write_page(struct vm_area_struct * vma,
+static int filemap_write_page(struct file *file,
 			      unsigned long offset,
 			      unsigned long page,
 			      int wait)
 {
 	int result;
-	struct file * file;
 	struct dentry * dentry;
 	struct inode * inode;
 
-	file = vma->vm_file;
 	dentry = file->f_dentry;
 	inode = dentry->d_inode;
 
 	/*
 	 * If a task terminates while we're swapping the page, the vma and
-	 * and file could be released ... increment the count to be safe.
+	 * and file could be released ... try_to_swap_out has done a get_file.
+	 * vma/file is guaranteed to exist in the unmap/sync cases because 
+	 * mmap_sem is held.
 	 */
-	get_file(file);
 	result = do_write_page(inode, file, (const char *) page, offset);
-	fput(file);
 	return result;
 }
 

@@ -1478,9 +1476,9 @@
  * at the same time..
  */
 extern void wakeup_bdflush(int);
-int filemap_swapout(struct vm_area_struct * vma, struct page * page)
+int filemap_swapout(struct page * page, struct file *file)
 {
-	int retval = filemap_write_page(vma, page->offset, page_address(page), 0);
+	int retval = filemap_write_page(file, page->offset, page_address(page), 0);
 	wakeup_bdflush(0);
 	return retval;
 }

@@ -1521,7 +1519,7 @@
 			return 0;
 		}
 	}
-	error = filemap_write_page(vma, address - vma->vm_start + vma->vm_offset, pageaddr, 1);
+	error = filemap_write_page(vma->vm_file, address - vma->vm_start + vma->vm_offset, pageaddr, 1);
 	page_cache_free(pageaddr);
 	return error;
 }

@@ -18,6 +18,7 @@
 #include <linux/pagemap.h>
 #include <linux/init.h>
 #include <linux/bigmem.h>
+#include <linux/file.h>
 
 #include <asm/pgtable.h>
 

@@ -38,6 +39,7 @@
 	unsigned long entry;
 	unsigned long page_addr;
 	struct page * page;
+	int (*swapout)(struct page *, struct file *);
 
 	pte = *page_table;
 	if (!pte_present(pte))

@@ -130,13 +132,16 @@
 	 * That would get rid of a lot of problems.
 	 */
 	flush_cache_page(vma, address);
-	if (vma->vm_ops && vma->vm_ops->swapout) {
+	if (vma->vm_ops && (swapout = vma->vm_ops->swapout)) {
 		int error;
+		struct file *file = vma->vm_file;
+		if (file) get_file(file);
 		pte_clear(page_table);
 		vma->vm_mm->rss--;
 		flush_tlb_page(vma, address);
 		vmlist_access_unlock(vma->vm_mm);
-		error = vma->vm_ops->swapout(vma, page);
+		error = swapout(page, file);
+		if (file) fput(file);
 		if (!error)
 			goto out_free_success;
 		__free_page(page);

@@ -687,11 +687,6 @@
 		end = end > mpnt->vm_end ? mpnt->vm_end : end;
 		size = end - st;
 
-		/*
-		 * The lock_kernel interlocks with kswapd try_to_swap_out
-		 * invoking a driver swapout() method, and being able to
-		 * guarantee vma existance.
-		 */
 		lock_kernel();
 		if (mpnt->vm_ops && mpnt->vm_ops->unmap)
 			mpnt->vm_ops->unmap(mpnt, st, size);