[PATCH] filemap_getpage can block when MAP_NONBLOCK specified

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>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

1 files changed, 6 insertions, 1 deletions

diff --git a/mm/filemap.c b/mm/filemap.c
index 439b2bea8e34..93595c327bbd 100644
--- a/mm/filemap.c
+++ b/mm/filemap.c
@@ -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:
         /*