[patch] filemap_getpage can block when MAP_NONBLOCK specified
From: Jeff Moyer (jmoyer_at_redhat.com)
Date: 03/30/05
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Date: Wed, 30 Mar 2005 15:15:46 -0500 To: linux-kernel@vger.kernel.org
Hello,
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;
Patch attached.
Thanks,
Jeff
--- linux-2.6.11/mm/filemap.c.orig 2005-03-30 14:57:02.252975936 -0500
+++ linux-2.6.11/mm/filemap.c 2005-03-30 15:02:51.808835368 -0500
@@ -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:
/*
-
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