From: Suparna Bhattacharya <suparna@in.ibm.com>

Filesystem aio read

Converts the wait for page to become uptodate (wait for page lock)
after readahead/readpage (in do_generic_mapping_read) to a retry



diff -upN reference/mm/filemap.c current/mm/filemap.c
--- reference/mm/filemap.c	2004-04-29 10:39:23.000000000 -0700
+++ current/mm/filemap.c	2004-04-29 10:39:23.000000000 -0700
@@ -713,7 +713,12 @@ page_not_up_to_date:
 			goto page_ok;
 
 		/* Get exclusive access to the page ... */
-		lock_page(page);
+
+		if (lock_page_wq(page, current->io_wait)) {
+			pr_debug("queued lock page \n");
+			error = -EIOCBRETRY;
+			goto sync_error;
+		}
 
 		/* Did it get unhashed before we got the lock? */
 		if (!page->mapping) {
@@ -735,13 +740,23 @@ readpage:
 		if (!error) {
 			if (PageUptodate(page))
 				goto page_ok;
-			wait_on_page_locked(page);
+			if (wait_on_page_locked_wq(page, current->io_wait)) {
+				pr_debug("queued wait_on_page \n");
+				error = -EIOCBRETRY;
+				goto sync_error;
+			}
+
 			if (PageUptodate(page))
 				goto page_ok;
 			error = -EIO;
 		}
 
-		/* UHHUH! A synchronous read error occurred. Report it */
+sync_error:
+		/* We don't have uptodate data in the page yet */
+		/* Could be due to an error or because we need to
+		 * retry when we get an async i/o notification.
+		 * Report the reason.
+		 */
 		desc->error = error;
 		page_cache_release(page);
 		break;