On Mon, Jul 12, 2021 at 05:40:05PM +0200, Jan Kara wrote:

JBD2 layer support triggers which are called when journaling layer moves
buffer to a certain state. We can use the frozen trigger, which gets
called when buffer data is frozen and about to be written out to the
journal, to compute block checksums for some buffer types (similarly as
does ocfs2). This avoids unnecessary repeated recomputation of the
checksum (at the cost of larger window where memory corruption won't be
caught by checksumming) and is even necessary when there are
unsynchronized updaters of the checksummed data.

So add argument to ext4_journal_get_write_access() and
ext4_journal_get_create_access() which describes buffer type so that
triggers can be set accordingly. This patch is mostly only a change of
prototype of the above mentioned functions and a few small helpers. Real
checksumming will come later.

Signed-off-by: Jan Kara <jack@suse.cz>

Looks good.  I would have preferred mention of the change to
ext4_walk_page_buffers in the commit description, but I guess this was
considered one of the "few small helpers".  :-)

The WARN_ON_ONCE change in jbd2_journal_set_triggers is a somewhat
tangentially-related unrelated change, but I think I understand why it
was made.

Reviewed-by: Theodore Ts'o <tytso@mit.edu>

						- Ted