What tree does this apply to? I get failures both for Jens' for-7.3/block and for-next trees in bfq-cgroups.c and bio.c
On Tue, Aug 11, 2026 at 02:47:40PM +0800, Yu Kuai wrote: > From: Yu Kuai <[email protected]> > > This RFC remains a preparatory series for the blkcg_mutex conversion > proposed in the related blkcg_mutex RFC v2 series [1]. That conversion > moves queue-local blkg topology synchronization from q->queue_lock to > q->blkcg_mutex, which is awkward while bios directly store queue-local > blkg references. > > v1 made the stored bio association queue-independent by replacing bi_blkg > with bi_blkcg, but a bio-owned blkg reference still had to be recovered by > looking up the bio's blkcg and current request_queue. Tao Cui reported that > cgroup removal deletes a dying blkg from the per-blkcg radix tree before a > throttled bio drops its reference. A later lookup for that pinned blkg then > fails, triggers the warning in bio_pinned_blkg(), and leaks the reference. > > v2 makes request_queue the authoritative lookup owner before converting the > bio association. A queue-owned rhashtable, keyed by the blkcg CSS ID, keeps > dying blkgs discoverable until their references drain while q->blkg_list > remains available for ordered walks. The bio conversion then stores and > pins the blkcg CSS, lazily creates a blkg only for users which need one, and > uses lookup-only access for completion and accounting paths which already > own a blkg reference. Async bio punt state is finally moved from blkg to > blkcg so punting alone does not instantiate a queue-local blkg. > > Changes since v1: > > - Add patch 1 to wait for every old blkg to leave q->blkg_list before a > shared request_queue is rebound, instead of treating root_blkg == NULL > as completion of asynchronous blkg teardown. > - Add patch 2 to replace the per-blkcg radix tree and lookup hint with a > request_queue rhashtable keyed by blkcg->css.id, as suggested by > Christoph Hellwig. Keep dying pinned blkgs in the hash until > blkg_release() so bio-owned references remain discoverable. > - Fold the v1 helper-only patch into patch 3, as suggested by Jan Kara and > Christoph Hellwig, and make bio_blkcg() naturally return NULL for an > unassociated bio. > - Rework patch 3 so blkg_lookup_create() acquires the bio-owned reference, > falls back to a live parent when creation or tryget fails, and updates > bi_blkcg when the returned blkg belongs to an ancestor. > - Make bio_blkg_lookup() lookup-only: it returns NULL unless BIO_BLKG_REF > is already set. Use bio_blkg() in the BFQ and IOCOST merge paths which > may need to create a blkg, while keeping blk_cgroup_bio_start() and > completion paths lookup-only. > - Move CSS online-reference handling into > bio_associate_blkcg_from_css(), including fallback to the root blkcg, so > bio_associate_blkcg() does not take a redundant reference. > - Keep the v1 async bio punt conversion as patch 4 and document that > async_bio_lock protects async_bios. > > Previous versions: > v1: https://lore.kernel.org/r/[email protected] > > Related series: > [1] RFC v2 blk-cgroup: protect blkgs with blkcg_mutex > https://lore.kernel.org/r/[email protected] > > Yu Kuai (4): > blk-cgroup: wait for old blkgs to leave queue before disk rebind > blk-cgroup: use a request_queue rhashtable for blkg lookup > 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 | 16 +- > block/bfq-iosched.c | 19 +- > block/bio.c | 22 +- > block/blk-cgroup-fc-appid.c | 10 +- > block/blk-cgroup.c | 348 ++++++++++++++---------- > block/blk-cgroup.h | 82 ++++-- > block/blk-core.c | 9 +- > 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 | 26 +- > include/linux/blk_types.h | 9 +- > include/linux/blkdev.h | 2 + > include/linux/writeback.h | 2 +- > mm/page_io.c | 13 +- > 24 files changed, 357 insertions(+), 245 deletions(-) > > > base-commit: f2690679ecf3a3151688ebef766dd2512ff95854 > -- > 2.51.0 ---end quoted text---
