vfs, writeback: replace FS_CGROUP_WRITEBACK with SB_I_CGROUPWB
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>
diff --git a/fs/ext2/super.c b/fs/ext2/super.c
index 549219d..900e19c 100644
--- a/fs/ext2/super.c
+++ b/fs/ext2/super.c
@@ -882,6 +882,7 @@
sb->s_flags = (sb->s_flags & ~MS_POSIXACL) |
((EXT2_SB(sb)->s_mount_opt & EXT2_MOUNT_POSIX_ACL) ?
MS_POSIXACL : 0);
+ sb->s_iflags |= SB_I_CGROUPWB;
if (le32_to_cpu(es->s_rev_level) == EXT2_GOOD_OLD_REV &&
(EXT2_HAS_COMPAT_FEATURE(sb, ~0U) ||
@@ -1543,7 +1544,7 @@
.name = "ext2",
.mount = ext2_mount,
.kill_sb = kill_block_super,
- .fs_flags = FS_REQUIRES_DEV | FS_CGROUP_WRITEBACK,
+ .fs_flags = FS_REQUIRES_DEV,
};
MODULE_ALIAS_FS("ext2");