From: Jeff Moyer <jmoyer@redhat.com>
Date: Sat, 16 Apr 2005 22:24:05 +0000 (-0700)
Subject: [PATCH] filemap_getpage can block when MAP_NONBLOCK specified
X-Git-Url: https://git.stricted.de/?a=commitdiff_plain;h=d345734267dbec642f4e34a9d392d2fd85b5fa9b;p=GitHub%2FLineageOS%2Fandroid_kernel_samsung_universal7580.git

[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>
---

diff --git a/mm/filemap.c b/mm/filemap.c
index 439b2bea8e3..93595c327bb 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:
 	/*