ext4: check s_chksum_driver when looking for bg csum presence
authorDarrick J. Wong <darrick.wong@oracle.com>
Tue, 14 Oct 2014 06:35:49 +0000 (02:35 -0400)
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>
Fri, 14 Nov 2014 16:47:57 +0000 (08:47 -0800)
commit209f5484ef126134f2d2f322246b0e4faf3c1fbd
tree1e786d6c9de35fadb1f92db11097d624f989341f
parent1f1ccdde66ed867e2a71297bdb6cf1b7c6a32351
ext4: check s_chksum_driver when looking for bg csum presence

commit 813d32f91333e4c33d5a19b67167c4bae42dae75 upstream.

Convert the ext4_has_group_desc_csum predicate to look for a checksum
driver instead of the metadata_csum flag and change the bg checksum
calculation function to look for GDT_CSUM before taking the crc16
path.

Without this patch, if we mount with ^uninit_bg,^metadata_csum and
later metadata_csum gets turned on by accident, the block group
checksum functions will incorrectly assume that checksumming is
enabled (metadata_csum) but that crc16 should be used
(!s_chksum_driver).  This is totally wrong, so fix the predicate
and the checksum formula selection.

(Granted, if the metadata_csum feature bit gets enabled on a live FS
then something underhanded is going on, but we could at least avoid
writing garbage into the on-disk fields.)

Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
Signed-off-by: Theodore Ts'o <tytso@mit.edu>
Reviewed-by: Dmitry Monakhov <dmonakhov@openvz.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
fs/ext4/ext4.h
fs/ext4/super.c