Hello, When writeback is executed asynchronously (e.g. for compression), bios are bounced to and issued by worker pool shared by all cgroups. This leads to significant priority inversions when cgroup IO control is in use - IOs for a low priority cgroup can tie down the workers forcing higher priority IOs to wait behind them. This patchset adds an bio punt mechanism to blkcg. A bio tagged with REQ_CGROUP_PUNT flag is bounced to the asynchronous issue context of the associated blkcg on bio_submit(). As the bios are issued from per-blkcg work items, there's no concern for priority inversions and it doesn't require invasive changes to the filesystems. The mechanism should be generally useful for IO control support across different filesystems. btrfs async path is simplified and is updated to use REQ_CGROUP_PUNT for submitting asynchronous bios. It's also updated to always and only account the original writeback bios against wbc so that cgroup inode writeback ownership arbitration isn't confused by downstream bios. This patchset contains the following 8 patches. The first three are my blkcg patches to implement the needed mechanisms. The latter five are Chris Mason's btrfs cleanup and update patches. Please let me know how the patches should be routed. Given that there currently aren't other users, it's likely the easiest to route all through btrfs tree. 0001-blkcg-writeback-Add-wbc-no_wbc_acct.patch 0002-blkcg-writeback-Implement-wbc_blkcg_css.patch 0003-blkcg-implement-REQ_CGROUP_PUNT.patch 0004-Btrfs-stop-using-btrfs_schedule_bio.patch 0005-Btrfs-delete-the-entire-async-bio-submission-framewo.patch 0006-Btrfs-only-associate-the-locked-page-with-one-async_.patch 0007-Btrfs-use-REQ_CGROUP_PUNT-for-worker-thread-submitte.patch 0008-Btrfs-extent_write_locked_range-should-attach-inode-.patch 0001-0003 implement wbc->no_wbc_acct, wbc_blkcg_css() and REQ_CGROUP_PUNT. 0004-0006 are prep patches to simplify / improve async bio submission. 0007 makes btrfs use REQ_CGROUP_PUNT for async bios. 0008 fixes wbc writeback accounting for IOs issued through extent_write_locked_range(). This patchset is also available in the following git branch. git://git.kernel.org/pub/scm/linux/kernel/git/tj/cgroup.git review-btrfs-cgroup-updates Thanks, diffstat follows. block/blk-cgroup.c | 54 +++++++++ block/blk-core.c | 3 fs/btrfs/compression.c | 16 +- fs/btrfs/compression.h | 3 fs/btrfs/ctree.h | 1 fs/btrfs/disk-io.c | 25 +--- fs/btrfs/extent_io.c | 15 +- fs/btrfs/inode.c | 61 ++++++++-- fs/btrfs/super.c | 1 fs/btrfs/volumes.c | 264 -------------------------------------------- fs/btrfs/volumes.h | 10 - fs/fs-writeback.c | 2 include/linux/backing-dev.h | 1 include/linux/blk-cgroup.h | 16 ++ include/linux/blk_types.h | 10 + include/linux/writeback.h | 24 +++- 16 files changed, 194 insertions(+), 312 deletions(-) -- tejun
