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b=L+v92v1A2R6bqo+k2ns+Apd0XuZhfJJRlDhcZRxfgYZBR6lBTySlcGwphZl9esPqc 6OapuqhkUgrZB5XbpeiKFE4FWmpX3fDYqnAWZ+Z5cik38+LKv17eC95gI/dBBW2maI QBtXzwx4Css+3kO8rrA5dxC6eWTTYjMJfj2lSIDJyX9WPH8eOB6Ln0exJvX33oYTJO CHj1Orsj3SZQz9ZomQddwDmGJoNO6y1P+zQ5V26DW3JHaWShU5qKy+zKNWu1trppZH XR4Bt0VV/FOH6OlQ1i8WQIXtA16nKQJtDvrM9pq+m+RFhwSgcAcBzQIdBMkDJt9hP/ ktPD12L2uaUcA== From: Yu Kuai To: Jens Axboe , Josef Bacik , Tejun Heo , Johannes Weiner , =?UTF-8?q?Michal=20Koutn=C3=BD?= , Jonathan Corbet , Shuah Khan , Randy Dunlap , Coly Li , Kent Overstreet , Alasdair Kergon , Mike Snitzer , Mikulas Patocka , Benjamin Marzinski , Song Liu , Li Nan , Xiao Ni , Andreas Gruenbacher , Matthew Wilcox , Jan Kara , Andrew Morton , Chris Li , Kairui Song , Kemeng Shi , Nhat Pham , Baoquan He , Barry Song , Youngjun Park , Nathan Chancellor , Nick Desaulniers , Bill Wendling , Justin Stitt Cc: Yu Kuai , Christoph Hellwig , Nilay Shroff , Tao Cui , linux-block@vger.kernel.org, cgroups@vger.kernel.org, linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org, linux-bcache@vger.kernel.org, dm-devel@lists.linux.dev, linux-raid@vger.kernel.org, gfs2@lists.linux.dev, linux-fsdevel@vger.kernel.org, linux-mm@kvack.org, llvm@lists.linux.dev Subject: [PATCH v2 0/3] blk-cgroup: store blkcg in bio before blkcg_mutex conversion Date: Sun, 13 Sep 2026 14:54:37 +0800 Message-ID: X-Mailer: git-send-email 2.51.0 MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Rspamd-Server: rspam04 X-Rspam-User: X-Stat-Signature: 8cdxw6mjdfh9fentop91e9t8hsjgdcfe X-Rspamd-Queue-Id: AE3B6140007 X-HE-Tag: 1789282497-187125 X-HE-Meta: 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 z/a+RuUd a6ho8Im7xq9VV2A9qQit55zNDCivHhGkk0Sc9WFr9gG2VgVNlgdGww7dwLElFzt0BeRnRqs5Qh8ADRcq4g7l4/bILjiHjfRm5k2Ozs9j6aNtTX7peqDluE39DNV7H/KN4wddsV7jg+PnNGogsgNAYFh6K6FT3Hzf+sWUGQvZXEv+LjlCTDF/EAvmnYipJUEUHNXyUdMIHigoK1PSbDCOnY18snds7SuJOZIEnx1Y3oc8cfwV5NM+KYAtMQg== Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: From: Yu Kuai This is v2 of the preparatory series for the blkcg_mutex conversion proposed in the related 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. Storing a blkg also ties a bio to one request_queue. A remapped bio must drop that reference and recreate the association for the new queue even when no blkcg policy needs it. Dying blkgs add another complication: they disappear from the per-blkcg lookup tree before all pinned bio references drain. Patch 1 makes request_queue the authoritative lookup owner. 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. Patch 2 stores and pins the queue-independent blkcg CSS in each bio. Queue-local blkgs are created lazily by policy users, then pinned until the bio changes devices or releases its cgroup state. Completion and accounting paths which do not create a blkg remain lookup-only. Patch 3 moves async bio punt state from blkg to blkcg, so punting alone does not instantiate a queue-local blkg. Changes since v1: - Rebase onto the latest block-7.3 branch. - In patch 2, require every blkg rhashtable lookup to run inside an explicit RCU read-side critical section. Annotate blkg_lookup_any(), blkg_lookup(), and recursive wrappers with __must_hold_shared(RCU) so Clang thread-safety analysis verifies the contract. - In patch 2, exclude BIO_BLKG_REF from the flags saved by dm_bio_record(), since restoring an ownership bit cannot recreate the associated blkg reference. - In patch 3, use scoped spinlock guards for async_bios and annotate the list with __guarded_by(). - Add Nilay Shroff's Reviewed-by to patch 1. Changes since RFC v3: - Drop the RFC prefix. - Add Christoph Hellwig's Reviewed-by to patch 1. - Add Tao Cui's Reviewed-by to patch 2. - In patch 2, relax blkg_lookup_any()/blkg_lookup() to also allow q->queue_lock as an alternative to the RCU read lock. Changes since RFC v2: - Drop the old patch 1 and send it separately as a bugfix for 7.3 and -stable, as suggested by Christoph Hellwig. - Rebase onto the latest for-7.3/block branch. - In the new patch 1, note that the remaining q->blkg_list walkers are cgroupfs/sysfs slow paths and can move to rhashtable iteration after the queue_lock-to-blkcg_mutex conversion. - In the new patch 1, explain the list_empty case in blkg_release(), and add an RCU lockdep assertion plus documentation that blkg_lookup_any() does not acquire a reference. Changes since RFC 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/20260823133045.970199-1-yukuai@kernel.org RFC v3: https://lore.kernel.org/r/20260818070641.756747-1-yukuai@kernel.org RFC v2: https://lore.kernel.org/r/20260811064744.1139446-1-yukuai@kernel.org RFC v1: https://lore.kernel.org/r/20260804065313.2092022-1-yukuai@kernel.org Related series: [1] RFC v2 blk-cgroup: protect blkgs with blkcg_mutex https://lore.kernel.org/r/20260724123037.3004560-1-yukuai@kernel.org Yu Kuai (3): 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 | 18 +- block/bfq-iosched.c | 19 +- block/bio.c | 22 +- block/blk-cgroup-fc-appid.c | 10 +- block/blk-cgroup-rwstat.h | 2 +- block/blk-cgroup.c | 358 ++++++++++++++---------- block/blk-cgroup.h | 93 ++++-- 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 | 3 +- block/blk-throttle.h | 2 +- drivers/md/bcache/request.c | 2 +- drivers/md/dm-bio-record.h | 3 +- drivers/md/dm.c | 2 +- drivers/md/md.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 | 12 +- 25 files changed, 391 insertions(+), 237 deletions(-) base-commit: fc34aff88b3bd22146745c75cff0abb3c067cf42 -- 2.51.0