mm: make read_cache_page synchronous

Ensure pages are uptodate after returning from read_cache_page, which allows
us to cut out most of the filesystem-internal PageUptodate calls.

I didn't have a great look down the call chains, but this appears to fixes 7
possible use-before uptodate in hfs, 2 in hfsplus, 1 in jfs, a few in
ecryptfs, 1 in jffs2, and a possible cleared data overwritten with readpage in
block2mtd.  All depending on whether the filler is async and/or can return
with a !uptodate page.

Signed-off-by: Nick Piggin <npiggin@suse.de>
Cc: Hugh Dickins <hugh@veritas.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

fs/ntfs/file.c

@@ -236,8 +236,7 @@ do_non_resident_extend:
 			err = PTR_ERR(page);
 			goto init_err_out;
 		}
-		wait_on_page_locked(page);
-		if (unlikely(!PageUptodate(page) || PageError(page))) {
+		if (unlikely(PageError(page))) {
 			page_cache_release(page);
 			err = -EIO;
 			goto init_err_out;