jbd2: use offset_in_page() instead of manual calculation
This is a port to jbd2 of a patch which Namhyung Kim <namhyung@gmail.com>
originally made to fs/jbd.
Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
diff --git a/fs/jbd2/transaction.c b/fs/jbd2/transaction.c
index 10b5e3b..80f9b2a 100644
--- a/fs/jbd2/transaction.c
+++ b/fs/jbd2/transaction.c
@@ -774,7 +774,7 @@
J_EXPECT_JH(jh, buffer_uptodate(jh2bh(jh)),
"Possible IO failure.\n");
page = jh2bh(jh)->b_page;
- offset = ((unsigned long) jh2bh(jh)->b_data) & ~PAGE_MASK;
+ offset = offset_in_page(jh2bh(jh)->b_data);
source = kmap_atomic(page, KM_USER0);
/* Fire data frozen trigger just before we copy the data */
jbd2_buffer_frozen_trigger(jh, source + offset,
