Re: [RFC PATCH v2 0/4] blk-cgroup: store blkcg in bio before blkcg_mutex conversion
"yu kuai" <[email protected]>
| Newsgroups | gmane.linux.kernel,gmane.linux.kernel.cgroups,gmane.linux.documentation,gmane.linux.block,gmane.linux.kernel.bcache.devel,gmane.linux.raid,gmane.linux.file-systems,gmane.linux.kernel.mm |
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| Message-ID | <[email protected]> |
Hi, 在 2026/8/14 14:45, Christoph Hellwig 写道: > 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 Oh, just realize this set is cooked based on Jens' initial for-7.3/block branch. With the other set that is already applied: 30d0c34b72f8 (HEAD -> block-7.3-blkg_list-rhashtable) blk-cgroup: move async bio punt state to blkcg 1aa13cdcc027 blk-cgroup: store blkcg in bio instead of blkg 058ff5f9c8ac blk-cgroup: use a request_queue rhashtable for blkg lookup fefb6604e496 blk-cgroup: wait for old blkgs to leave queue before disk rebind f2690679ecf3 (for-7.3/block) blk-cgroup: factor policy pd teardown loop into helper ed3105cce735 blk-cgroup: skip dying blkg in blkcg_activate_policy() 415bd622f1a3 blk-cgroup: fix race between policy activation and blkg destruction 4cc0299aea5d blk-cgroup: protect q->blkg_list iteration in blkg_destroy_all() with blkcg_mutex f5098b6bae76 (tag: v7.2-rc5, block-7.2) Linux 7.2-rc5 I'll rebase to the latest for-7.3/block branch in the next version. > > 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--- > -- Thanks, Kuai