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originally made to fs/jbd.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 10b5e3b1ca8b36ce32c1a978bf492fddd2bb9744..80f9b2a3880b1be1af7b9138f5dfdea93ff3a6bd 100644 (file)
--- a/fs/jbd2/transaction.c
+++ b/fs/jbd2/transaction.c
@@ -774,7 +774,7 @@ done:
                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,