[patch 015/198] filemap_getpage can block when MAP_NONBLOCK specified

[patch 015/198] filemap_getpage can block when MAP_NONBLOCK specified

[akpm]

From: Jeff Moyer <jmoyer@redhat.com>

We will return NULL from filemap_getpage when a page does not exist in the
page cache and MAP_NONBLOCK is specified, here:

	page = find_get_page(mapping, pgoff);
	if (!page) {
		if (nonblock)
			return NULL;
		goto no_cached_page;
	}

But we forget to do so when the page in the cache is not uptodate.  The
following could result in a blocking call:

	/*
	 * Ok, found a page in the page cache, now we need to check
	 * that it's up-to-date.
	 */
	if (!PageUptodate(page))
		goto page_not_uptodate;



Signed-off-by: Andrew Morton <akpm@osdl.org>
---

 25-akpm/mm/filemap.c |    7 ++++++-
 1 files changed, 6 insertions(+), 1 deletion(-)

diff -puN mm/filemap.c~filemap_getpage-can-block-when-map_nonblock-specified mm/filemap.c
--- 25/mm/filemap.c~filemap_getpage-can-block-when-map_nonblock-specified	2005-04-12 03:21:07.024069080 -0700
+++ 25-akpm/mm/filemap.c	2005-04-12 03:21:07.028068472 -0700
@@ -1379,8 +1379,13 @@ retry_find:
 	 * Ok, found a page in the page cache, now we need to check
 	 * that it's up-to-date.
 	 */
-	if (!PageUptodate(page))
+	if (!PageUptodate(page)) {
+		if (nonblock) {
+			page_cache_release(page);
+			return NULL;
+		}
 		goto page_not_uptodate;
+	}
 
 success:
 	/*
_