ext4: implement cgroup writeback support

For ordered and writeback data modes, all data IOs go through
ext4_io_submit.  This patch adds cgroup writeback support by invoking
wbc_init_bio() from io_submit_init_bio() and wbc_account_io() in
io_submit_add_bh().  Journal data which is written by jbd2 worker is
left alone by this patch and will always be written out from the root
cgroup.

ext4_fill_super() is updated to set MS_CGROUPWB when data mode is
either ordered or writeback.  In journaled data mode, most IOs become
synchronous through the journal and enabling cgroup writeback support
doesn't make much sense or difference.  Journaled data mode is left
alone.

Lightly tested with sequential data write workload.  Behaves as
expected.

Signed-off-by: Tejun Heo <tj@kernel.org>
Signed-off-by: Theodore Ts'o <tytso@mit.edu>

diff --git a/fs/ext4/page-io.c b/fs/ext4/page-io.c
index a917bfe3e70c420ce137afe1b5ff92e74f1e9f0d..58ab2e3dd11471abee971bc44026a68072cb38a0 100644 (file)
--- a/fs/ext4/page-io.c
+++ b/fs/ext4/page-io.c
@@ -383,6 +383,7 @@ static int io_submit_init_bio(struct ext4_io_submit *io,
        bio = bio_alloc(GFP_NOIO, min(nvecs, BIO_MAX_PAGES));
        if (!bio)
                return -ENOMEM;
+       wbc_init_bio(io->io_wbc, bio);
        bio->bi_iter.bi_sector = bh->b_blocknr * (bh->b_size >> 9);
        bio->bi_bdev = bh->b_bdev;
        bio->bi_end_io = ext4_end_bio;
@@ -411,6 +412,7 @@ submit_and_retry:
        ret = bio_add_page(io->io_bio, page, bh->b_size, bh_offset(bh));
        if (ret != bh->b_size)
                goto submit_and_retry;
+       wbc_account_io(io->io_wbc, page, bh->b_size);
        io->io_next_block++;
        return 0;
 }

diff --git a/fs/ext4/super.c b/fs/ext4/super.c
index 58987b5c514b2baf433801dee0525d05c4525906..d2c9a7985fd78351dd3bad31eaca502c52a0e4f4 100644 (file)
--- a/fs/ext4/super.c
+++ b/fs/ext4/super.c
@@ -3643,6 +3643,8 @@ static int ext4_fill_super(struct super_block *sb, void *data, int silent)
                }
                if (test_opt(sb, DELALLOC))
                        clear_opt(sb, DELALLOC);
+       } else {
+               sb->s_iflags |= SB_I_CGROUPWB;
        }
 
        sb->s_flags = (sb->s_flags & ~MS_POSIXACL) |