[PATCH] filemap_getpage can block when MAP_NONBLOCK specified
Jeff Moyer [Sat, 16 Apr 2005 22:24:05 +0000 (15:24 -0700)]
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>

mm/filemap.c

index 439b2be..93595c3 100644 (file)
@@ -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:
        /*