FS_CGROUP_WRITEBACK indicates whether a file_system_type supports
cgroup writeback; however, different super_blocks of the same
file_system_type may or may not support cgroup writeback depending on
filesystem options. This patch replaces FS_CGROUP_WRITEBACK with a
per-super_block flag.
super_block->s_flags carries some internal flags in the high bits but
it's exposd to userland through uapi header and running out of space
anyway. This patch adds a new field super_block->s_iflags to carry
kernel-internal flags. It is currently only used by the new
SB_I_CGROUPWB flag whose concatenated and abbreviated name is for
consistency with other super_block flags.
ext2_fill_super() is updated to set SB_I_CGROUPWB.
v2: Added super_block->s_iflags instead of stealing another high bit
from sb->s_flags as suggested by Christoph and Jan.
Signed-off-by: Tejun Heo <tj@kernel.org>
Cc: Alexander Viro <viro@zeniv.linux.org.uk>
Cc: linux-fsdevel@vger.kernel.org
Cc: Christoph Hellwig <hch@infradead.org>
Cc: Jan Kara <jack@suse.cz>
Cc: linux-ext4@vger.kernel.org
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Jens Axboe <axboe@fb.com>
46b15caa7c