On 6/27/19 2:39 PM, Tejun Heo wrote: > Hello, > > This patchset contains only the block part of the following > > [1] [PATCHSET v2 btrfs/for-next] blkcg, btrfs: fix cgroup writeback support > > with the following changes > > * wbc_account_io() is renamed to wbc_account_cgroup_owner() and > wbc->no_account_io to wbc->no_cgroup_owner for clarity. > > 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 and updates btrfs to > issue async IOs through it. 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. Applied for 5.3, thanks Tejun. -- Jens Axboe
