kernel/block/blk-cgroup.c, branch linux-rolling-stable

blk-cgroup: fix possible deadlock while configuring policy

2025-11-13T20:36:52Z

[ Upstream commit 5d726c4dbeeddef612e6bed27edd29733f4d13af ] Following deadlock can be triggered easily by lockdep: WARNING: possible circular locking dependency detected 6.17.0-rc3-00124-ga12c2658ced0 #1665 Not tainted ------------------------------------------------------ check/1334 is trying to acquire lock: ff1100011d9d0678 (&q->sysfs_lock){+.+.}-{4:4}, at: blk_unregister_queue+0x53/0x180 but task is already holding lock: ff1100011d9d00e0 (&q->q_usage_counter(queue)#3){++++}-{0:0}, at: del_gendisk+0xba/0x110 which lock already depends on the new lock. the existing dependency chain (in reverse order) is: -> #2 (&q->q_usage_counter(queue)#3){++++}-{0:0}: blk_queue_enter+0x40b/0x470 blkg_conf_prep+0x7b/0x3c0 tg_set_limit+0x10a/0x3e0 cgroup_file_write+0xc6/0x420 kernfs_fop_write_iter+0x189/0x280 vfs_write+0x256/0x490 ksys_write+0x83/0x190 __x64_sys_write+0x21/0x30 x64_sys_call+0x4608/0x4630 do_syscall_64+0xdb/0x6b0 entry_SYSCALL_64_after_hwframe+0x76/0x7e -> #1 (&q->rq_qos_mutex){+.+.}-{4:4}: __mutex_lock+0xd8/0xf50 mutex_lock_nested+0x2b/0x40 wbt_init+0x17e/0x280 wbt_enable_default+0xe9/0x140 blk_register_queue+0x1da/0x2e0 __add_disk+0x38c/0x5d0 add_disk_fwnode+0x89/0x250 device_add_disk+0x18/0x30 virtblk_probe+0x13a3/0x1800 virtio_dev_probe+0x389/0x610 really_probe+0x136/0x620 __driver_probe_device+0xb3/0x230 driver_probe_device+0x2f/0xe0 __driver_attach+0x158/0x250 bus_for_each_dev+0xa9/0x130 driver_attach+0x26/0x40 bus_add_driver+0x178/0x3d0 driver_register+0x7d/0x1c0 __register_virtio_driver+0x2c/0x60 virtio_blk_init+0x6f/0xe0 do_one_initcall+0x94/0x540 kernel_init_freeable+0x56a/0x7b0 kernel_init+0x2b/0x270 ret_from_fork+0x268/0x4c0 ret_from_fork_asm+0x1a/0x30 -> #0 (&q->sysfs_lock){+.+.}-{4:4}: __lock_acquire+0x1835/0x2940 lock_acquire+0xf9/0x450 __mutex_lock+0xd8/0xf50 mutex_lock_nested+0x2b/0x40 blk_unregister_queue+0x53/0x180 __del_gendisk+0x226/0x690 del_gendisk+0xba/0x110 sd_remove+0x49/0xb0 [sd_mod] device_remove+0x87/0xb0 device_release_driver_internal+0x11e/0x230 device_release_driver+0x1a/0x30 bus_remove_device+0x14d/0x220 device_del+0x1e1/0x5a0 __scsi_remove_device+0x1ff/0x2f0 scsi_remove_device+0x37/0x60 sdev_store_delete+0x77/0x100 dev_attr_store+0x1f/0x40 sysfs_kf_write+0x65/0x90 kernfs_fop_write_iter+0x189/0x280 vfs_write+0x256/0x490 ksys_write+0x83/0x190 __x64_sys_write+0x21/0x30 x64_sys_call+0x4608/0x4630 do_syscall_64+0xdb/0x6b0 entry_SYSCALL_64_after_hwframe+0x76/0x7e other info that might help us debug this: Chain exists of: &q->sysfs_lock --> &q->rq_qos_mutex --> &q->q_usage_counter(queue)#3 Possible unsafe locking scenario: CPU0 CPU1 ---- ---- lock(&q->q_usage_counter(queue)#3); lock(&q->rq_qos_mutex); lock(&q->q_usage_counter(queue)#3); lock(&q->sysfs_lock); Root cause is that queue_usage_counter is grabbed with rq_qos_mutex held in blkg_conf_prep(), while queue should be freezed before rq_qos_mutex from other context. The blk_queue_enter() from blkg_conf_prep() is used to protect against policy deactivation, which is already protected with blkcg_mutex, hence convert blk_queue_enter() to blkcg_mutex to fix this problem. Meanwhile, consider that blkcg_mutex is held after queue is freezed from policy deactivation, also convert blkg_alloc() to use GFP_NOIO. Signed-off-by: Yu Kuai Reviewed-by: Ming Lei Signed-off-by: Jens Axboe Signed-off-by: Sasha Levin

block: Remove elevator_lock usage from blkg_conf frozen operations

2025-10-23T14:24:37Z

[ Upstream commit 08823e89e3e269bf4c4a20b4c24a8119920cc7a4 ] Remove the acquisition and release of q->elevator_lock in the blkg_conf_open_bdev_frozen() and blkg_conf_exit_frozen() functions. The elevator lock is no longer needed in these code paths since commit 78c271344b6f ("block: move wbt_enable_default() out of queue freezing from sched ->exit()") which introduces `disk->rqos_state_mutex` for protecting wbt state change, and not necessary to abuse elevator_lock for this purpose. This change helps to solve the lockdep warning reported from Yu Kuai[1]. Pass blktests/throtl with lockdep enabled. Links: https://lore.kernel.org/linux-block/e5e7ac3f-2063-473a-aafb-4d8d43e5576e@yukuai.org.cn/ [1] Fixes: commit 78c271344b6f ("block: move wbt_enable_default() out of queue freezing from sched ->exit()") Signed-off-by: Ming Lei Reviewed-by: Nilay Shroff Signed-off-by: Jens Axboe Signed-off-by: Sasha Levin

blk-throttle: fix access race during throttle policy activation

2025-10-15T10:03:26Z

[ Upstream commit bd9fd5be6bc0836820500f68fff144609fbd85a9 ] On repeated cold boots we occasionally hit a NULL pointer crash in blk_should_throtl() when throttling is consulted before the throttle policy is fully enabled for the queue. Checking only q->td != NULL is insufficient during early initialization, so blkg_to_pd() for the throttle policy can still return NULL and blkg_to_tg() becomes NULL, which later gets dereferenced. Unable to handle kernel NULL pointer dereference at virtual address 0000000000000156 ... pc : submit_bio_noacct+0x14c/0x4c8 lr : submit_bio_noacct+0x48/0x4c8 sp : ffff800087f0b690 x29: ffff800087f0b690 x28: 0000000000005f90 x27: ffff00068af393c0 x26: 0000000000080000 x25: 000000000002fbc0 x24: ffff000684ddcc70 x23: 0000000000000000 x22: 0000000000000000 x21: 0000000000000000 x20: 0000000000080000 x19: ffff000684ddcd08 x18: ffffffffffffffff x17: 0000000000000000 x16: ffff80008132a550 x15: 0000ffff98020fff x14: 0000000000000000 x13: 1fffe000d11d7021 x12: ffff000688eb810c x11: ffff00077ec4bb80 x10: ffff000688dcb720 x9 : ffff80008068ef60 x8 : 00000a6fb8a86e85 x7 : 000000000000111e x6 : 0000000000000002 x5 : 0000000000000246 x4 : 0000000000015cff x3 : 0000000000394500 x2 : ffff000682e35e40 x1 : 0000000000364940 x0 : 000000000000001a Call trace: submit_bio_noacct+0x14c/0x4c8 verity_map+0x178/0x2c8 __map_bio+0x228/0x250 dm_submit_bio+0x1c4/0x678 __submit_bio+0x170/0x230 submit_bio_noacct_nocheck+0x16c/0x388 submit_bio_noacct+0x16c/0x4c8 submit_bio+0xb4/0x210 f2fs_submit_read_bio+0x4c/0xf0 f2fs_mpage_readpages+0x3b0/0x5f0 f2fs_readahead+0x90/0xe8 Tighten blk_throtl_activated() to also require that the throttle policy bit is set on the queue: return q->td != NULL && test_bit(blkcg_policy_throtl.plid, q->blkcg_pols); This prevents blk_should_throtl() from accessing throttle group state until policy data has been attached to blkgs. Fixes: a3166c51702b ("blk-throttle: delay initialization until configuration") Co-developed-by: Liang Jie Signed-off-by: Liang Jie Signed-off-by: Han Guangjiang Reviewed-by: Yu Kuai Signed-off-by: Jens Axboe Signed-off-by: Sasha Levin

blk-cgroup: remove redundant __GFP_NOWARN

2025-08-11T13:59:40Z

Commit 16f5dfbc851b ("gfp: include __GFP_NOWARN in GFP_NOWAIT") made GFP_NOWAIT implicitly include __GFP_NOWARN. Therefore, explicit __GFP_NOWARN combined with GFP_NOWAIT (e.g., `GFP_NOWAIT | __GFP_NOWARN`) is now redundant. Let's clean up these redundant flags across subsystems. Signed-off-by: Qianfeng Rong Acked-by: Tejun Heo Link: https://lore.kernel.org/r/20250809141358.168781-1-rongqianfeng@vivo.com Signed-off-by: Jens Axboe

Merge tag 'cgroup-for-6.16' of git://git.kernel.org/pub/scm/linux/kernel/git/tj/cgroup

2025-05-28T03:59:53Z

Pull cgroup updates from Tejun Heo: - cgroup rstat shared the tracking tree across all controllers with the rationale being that a cgroup which is using one resource is likely to be using other resources at the same time (ie. if something is allocating memory, it's probably consuming CPU cycles). However, this turned out to not scale very well especially with memcg using rstat for internal operations which made memcg stat read and flush patterns substantially different from other controllers. JP Kobryn split the rstat tree per controller. - cgroup BPF support was hooking into cgroup init/exit paths directly. Convert them to use a notifier chain instead so that other usages can be added easily. The two of the patches which implement this are mislabeled as belonging to sched_ext instead of cgroup. Sorry. - Relatively minor cpuset updates - Documentation updates * tag 'cgroup-for-6.16' of git://git.kernel.org/pub/scm/linux/kernel/git/tj/cgroup: (23 commits) sched_ext: Convert cgroup BPF support to use cgroup_lifetime_notifier sched_ext: Introduce cgroup_lifetime_notifier cgroup: Minor reorganization of cgroup_create() cgroup, docs: cpu controller's interaction with various scheduling policies cgroup, docs: convert space indentation to tab indentation cgroup: avoid per-cpu allocation of size zero rstat cpu locks cgroup, docs: be specific about bandwidth control of rt processes cgroup: document the rstat per-cpu initialization cgroup: helper for checking rstat participation of css cgroup: use subsystem-specific rstat locks to avoid contention cgroup: use separate rstat trees for each subsystem cgroup: compare css to cgroup::self in helper for distingushing css cgroup: warn on rstat usage by early init subsystems cgroup/cpuset: drop useless cpumask_empty() in compute_effective_exclusive_cpumask() cgroup/rstat: Improve cgroup_rstat_push_children() documentation cgroup: fix goto ordering in cgroup_init() cgroup: fix pointer check in css_rstat_init() cgroup/cpuset: Add warnings to catch inconsistency in exclusive CPUs cgroup/cpuset: Fix obsolete comment in cpuset_css_offline() cgroup/cpuset: Always use cpu_active_mask ...

cgroup: use subsystem-specific rstat locks to avoid contention

2025-05-19T20:29:42Z

It is possible to eliminate contention between subsystems when updating/flushing stats by using subsystem-specific locks. Let the existing rstat locks be dedicated to the cgroup base stats and rename them to reflect that. Add similar locks to the cgroup_subsys struct for use with individual subsystems. Lock initialization is done in the new function ss_rstat_init(ss) which replaces cgroup_rstat_boot(void). If NULL is passed to this function, the global base stat locks will be initialized. Otherwise, the subsystem locks will be initialized. Change the existing lock helper functions to accept a reference to a css. Then within these functions, conditionally select the appropriate locks based on the subsystem affiliation of the given css. Add helper functions for this selection routine to avoid repeated code. Signed-off-by: JP Kobryn Signed-off-by: Tejun Heo

block: don't autoload drivers on blk-cgroup configuration

2025-04-24T13:35:23Z

Loading a driver just to configure blk-cgroup doesn't make sense, as that assumes and already existing device. Signed-off-by: Christoph Hellwig Reviewed-by: Christian Brauner Acked-by: Tejun Heo Link: https://lore.kernel.org/r/20250423053810.1683309-5-hch@lst.de Signed-off-by: Jens Axboe

block: don't autoload drivers on stat

2025-04-24T13:35:23Z

blkdev_get_no_open can trigger the legacy autoload of block drivers. A simple stat of a block device has not historically done that, so disable this behavior again. Fixes: 9abcfbd235f5 ("block: Add atomic write support for statx") Signed-off-by: Christoph Hellwig Reviewed-by: Christian Brauner Acked-by: Tejun Heo Link: https://lore.kernel.org/r/20250423053810.1683309-4-hch@lst.de Signed-off-by: Jens Axboe

cgroup: change rstat function signatures from cgroup-based to css-based

2025-04-04T20:06:25Z

This non-functional change serves as preparation for moving to subsystem-based rstat trees. To simplify future commits, change the signatures of existing cgroup-based rstat functions to become css-based and rename them to reflect that. Though the signatures have changed, the implementations have not. Within these functions use the css->cgroup pointer to obtain the associated cgroup and allow code to function the same just as it did before this patch. At applicable call sites, pass the subsystem-specific css pointer as an argument or pass a pointer to cgroup::self if not in subsystem context. Note that cgroup_rstat_updated_list() and cgroup_rstat_push_children() are not altered yet since there would be a larger amount of css to cgroup conversions which may overcomplicate the code at this intermediate phase. Signed-off-by: JP Kobryn Signed-off-by: Tejun Heo

Merge tag 'for-6.15/block-20250322' of git://git.kernel.dk/linux

2025-03-27T01:08:55Z

Pull block updates from Jens Axboe: - Fixes for integrity handling - NVMe pull request via Keith: - Secure concatenation for TCP transport (Hannes) - Multipath sysfs visibility (Nilay) - Various cleanups (Qasim, Baruch, Wang, Chen, Mike, Damien, Li) - Correct use of 64-bit BARs for pci-epf target (Niklas) - Socket fix for selinux when used in containers (Peijie) - MD pull request via Yu: - fix recovery can preempt resync (Li Nan) - fix md-bitmap IO limit (Su Yue) - fix raid10 discard with REQ_NOWAIT (Xiao Ni) - fix raid1 memory leak (Zheng Qixing) - fix mddev uaf (Yu Kuai) - fix raid1,raid10 IO flags (Yu Kuai) - some refactor and cleanup (Yu Kuai) - Series cleaning up and fixing bugs in the bad block handling code - Improve support for write failure simulation in null_blk - Various lock ordering fixes - Fixes for locking for debugfs attributes - Various ublk related fixes and improvements - Cleanups for blk-rq-qos wait handling - blk-throttle fixes - Fixes for loop dio and sync handling - Fixes and cleanups for the auto-PI code - Block side support for hardware encryption keys in blk-crypto - Various cleanups and fixes * tag 'for-6.15/block-20250322' of git://git.kernel.dk/linux: (105 commits) nvmet: replace max(a, min(b, c)) by clamp(val, lo, hi) nvme-tcp: fix selinux denied when calling sock_sendmsg nvmet: pci-epf: Always configure BAR0 as 64-bit nvmet: Remove duplicate uuid_copy nvme: zns: Simplify nvme_zone_parse_entry() nvmet: pci-epf: Remove redundant 'flush_workqueue()' calls nvmet-fc: Remove unused functions nvme-pci: remove stale comment nvme-fc: Utilise min3() to simplify queue count calculation nvme-multipath: Add visibility for queue-depth io-policy nvme-multipath: Add visibility for numa io-policy nvme-multipath: Add visibility for round-robin io-policy nvmet: add tls_concat and tls_key debugfs entries nvmet-tcp: support secure channel concatenation nvmet: Add 'sq' argument to alloc_ctrl_args nvme-fabrics: reset admin connection for secure concatenation nvme-tcp: request secure channel concatenation nvme-keyring: add nvme_tls_psk_refresh() nvme: add nvme_auth_derive_tls_psk() nvme: add nvme_auth_generate_digest() ...