[RFC PATCH v1 0/3] blk-cgroup: store blkcg in bio before blkcg_mutex conversion
Yu Kuai <[email protected]>
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From: Yu Kuai <[email protected]> This RFC is a preparatory series for the blkcg_mutex conversion proposed in the blkcg_mutex RFC v2 series [1]. That series moves queue-local blkg topology synchronization from q->queue_lock to q->blkcg_mutex. A direct conversion is awkward while bios store queue-local blkg references, because bio allocation, bio_set_dev(), remap and clone paths can run in contexts where creating a missing blkg must not sleep or is unnecessary. This set makes the bio association queue-independent by storing the blkcg in the bio instead of a blkg. A blkg is looked up from the bio's blkcg and current bdev only when blkcg policy or accounting code needs it. The first successful policy lookup pins the blkg with a bio-owned reference tracked by BIO_BLKG_REF; the reference is dropped when the bio cgroup association is cleared or when bio_set_dev() changes the lookup key. Patch 1 adds accessors for the current bio cgroup state and factors out the release path. Patch 2 switches the stored bio association from blkg to blkcg, adds lookup/create helpers for policy users, and converts the blkcg policies and cloned-bio users. Patch 3 moves async bio punt state from blkg to blkcg so punted bios do not instantiate a queue-local blkg when no policy needs one. This is v1 of this preparatory set; there is no previous version. Related series: [1] RFC v2 blk-cgroup: protect blkgs with blkcg_mutex https://lore.kernel.org/r/[email protected] Yu Kuai (3): blk-cgroup: add helpers for bio cgroup state blk-cgroup: store blkcg in bio instead of blkg blk-cgroup: move async bio punt state to blkcg Documentation/admin-guide/cgroup-v2.rst | 2 +- block/bfq-cgroup.c | 14 +- block/bfq-iosched.c | 18 +- block/bio.c | 22 +-- block/blk-cgroup-fc-appid.c | 10 +- block/blk-cgroup.c | 251 +++++++++++++++--------- block/blk-cgroup.h | 40 +++- block/blk-crypto-fallback.c | 2 +- block/blk-iocost.c | 12 +- block/blk-iolatency.c | 11 +- block/blk-ioprio.c | 2 +- block/blk-throttle.c | 2 +- block/blk-throttle.h | 2 +- drivers/md/bcache/request.c | 2 +- drivers/md/dm.c | 2 +- drivers/md/md.c | 2 +- drivers/nvdimm/nd_virtio.c | 2 +- fs/gfs2/lops.c | 3 +- include/linux/bio.h | 20 +- include/linux/blk_types.h | 9 +- include/linux/writeback.h | 2 +- mm/page_io.c | 10 +- 22 files changed, 268 insertions(+), 172 deletions(-) base-commit: f2690679ecf3a3151688ebef766dd2512ff95854 -- 2.51.0