[PATCH] ecryptfs: handle AOP_TRUNCATED_PAGE better

- In fact we don't have to fail if AOP_TRUNCATED_PAGE was returned from
prepare_write or commit_write. It is beter to retry attempt where it
is possible.

- Rearange ecryptfs_get_lower_page() error handling logic, make it more clean.

Signed-off-by: Dmitriy Monakhov <[e-mail]>
Acked-by: Michael Halcrow <[e-mail]>
Signed-off-by: Andrew Morton <[e-mail]>
Signed-off-by: Linus Torvalds <[e-mail]>

fs/ecryptfs/mmap.c

···
 	const struct address_space_operations *lower_a_ops;
 	u64 file_size;
 
+retry:
 	header_page = grab_cache_page(lower_inode->i_mapping, 0);
 	if (!header_page) {
 		ecryptfs_printk(KERN_ERR, "grab_cache_page for "
···
 	lower_a_ops = lower_inode->i_mapping->a_ops;
 	rc = lower_a_ops->prepare_write(lower_file, header_page, 0, 8);
 	if (rc) {
-		if (rc == AOP_TRUNCATED_PAGE)
+		if (rc == AOP_TRUNCATED_PAGE) {
 			ecryptfs_release_lower_page(header_page, 0);
-		else
+			goto retry;
+		} else
 			ecryptfs_release_lower_page(header_page, 1);
 		goto out;
 	}
···
 	if (rc < 0)
 		ecryptfs_printk(KERN_ERR, "Error commiting header page "
 				"write\n");
-	if (rc == AOP_TRUNCATED_PAGE)
+	if (rc == AOP_TRUNCATED_PAGE) {
 		ecryptfs_release_lower_page(header_page, 0);
-	else
+		goto retry;
+	} else
 		ecryptfs_release_lower_page(header_page, 1);
 	lower_inode->i_mtime = lower_inode->i_ctime = CURRENT_TIME;
 	mark_inode_dirty_sync(inode);
···
 {
 	int rc = 0;
 
+retry:
 	*lower_page = grab_cache_page(lower_inode->i_mapping, lower_page_index);
 	if (!(*lower_page)) {
 		rc = -EINVAL;
···
 							  byte_offset,
 							  region_bytes);
 	if (rc) {
-		ecryptfs_printk(KERN_ERR, "prepare_write for "
+		if (rc == AOP_TRUNCATED_PAGE) {
+			ecryptfs_release_lower_page(*lower_page, 0);
+			goto retry;
+		} else {
+			ecryptfs_printk(KERN_ERR, "prepare_write for "
 				"lower_page_index = [0x%.16x] failed; rc = "
 				"[%d]\n", lower_page_index, rc);
+			ecryptfs_release_lower_page(*lower_page, 1);
+			(*lower_page) = NULL;
+		}
 	}
 out:
-	if (rc && (*lower_page)) {
-		if (rc == AOP_TRUNCATED_PAGE)
-			ecryptfs_release_lower_page(*lower_page, 0);
-		else
-			ecryptfs_release_lower_page(*lower_page, 1);
-		(*lower_page) = NULL;
-	}
 	return rc;
 }