summaryrefslogtreecommitdiff
path: root/block/blk-cgroup.c
AgeCommit message (Collapse)AuthorFilesLines
2025-04-24block: don't autoload drivers on blk-cgroup configurationChristoph Hellwig1-1/+1
Loading a driver just to configure blk-cgroup doesn't make sense, as that assumes and already existing device. Signed-off-by: Christoph Hellwig <hch@lst.de> Reviewed-by: Christian Brauner <brauner@kernel.org> Acked-by: Tejun Heo <tj@kernel.org> Link: https://lore.kernel.org/r/20250423053810.1683309-5-hch@lst.de Signed-off-by: Jens Axboe <axboe@kernel.dk>
2025-04-24block: don't autoload drivers on statChristoph Hellwig1-1/+1
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 <hch@lst.de> Reviewed-by: Christian Brauner <brauner@kernel.org> Acked-by: Tejun Heo <tj@kernel.org> Link: https://lore.kernel.org/r/20250423053810.1683309-4-hch@lst.de Signed-off-by: Jens Axboe <axboe@kernel.dk>
2025-03-26Merge tag 'for-6.15/block-20250322' of git://git.kernel.dk/linuxLinus Torvalds1-10/+63
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() ...
2025-03-24Merge tag 'cgroup-for-6.15' of ↵Linus Torvalds1-2/+6
git://git.kernel.org/pub/scm/linux/kernel/git/tj/cgroup Pull cgroup updates from Tejun Heo: - Add deprecation info messages to cgroup1-only features - rstat updates including a bug fix and breaking up a critical section to reduce interrupt latency impact - Other misc and doc updates * tag 'cgroup-for-6.15' of git://git.kernel.org/pub/scm/linux/kernel/git/tj/cgroup: cgroup: rstat: Cleanup flushing functions and locking cgroup/rstat: avoid disabling irqs for O(num_cpu) mm: Fix a build breakage in memcontrol-v1.c blk-cgroup: Simplify policy files registration cgroup: Update file naming comment cgroup: Add deprecation message to legacy freezer controller mm: Add transformation message for per-memcg swappiness RFC cgroup/cpuset-v1: Add deprecation messages to sched_relax_domain_level cgroup/cpuset-v1: Add deprecation messages to memory_migrate cgroup/cpuset-v1: Add deprecation messages to mem_exclusive and mem_hardwall cgroup: Print message when /proc/cgroups is read on v2-only system cgroup/blkio: Add deprecation messages to reset_stats cgroup/cpuset-v1: Add deprecation messages to memory_spread_page and memory_spread_slab cgroup/cpuset-v1: Add deprecation messages to sched_load_balance and memory_pressure_enabled cgroup, docs: Be explicit about independence of RT_GROUP_SCHED and non-cpu controllers cgroup/rstat: Fix forceidle time in cpu.stat cgroup/misc: Remove unused misc_cg_res_total_usage cgroup/cpuset: Move procfs cpuset attribute under cgroup-v1.c cgroup: update comment about dropping cgroup kn refs
2025-03-19block: correct locking order for protecting blk-wbt parametersNilay Shroff1-0/+51
The commit '245618f8e45f ("block: protect wbt_lat_usec using q-> elevator_lock")' introduced q->elevator_lock to protect updates to blk-wbt parameters when writing to the sysfs attribute wbt_ lat_usec and the cgroup attribute io.cost.qos. However, both these attributes also acquire q->rq_qos_mutex, leading to the following lockdep warning: ====================================================== WARNING: possible circular locking dependency detected 6.14.0-rc5+ #138 Not tainted ------------------------------------------------------ bash/5902 is trying to acquire lock: c000000085d495a0 (&q->rq_qos_mutex){+.+.}-{4:4}, at: wbt_init+0x164/0x238 but task is already holding lock: c000000085d498c8 (&q->elevator_lock){+.+.}-{4:4}, at: queue_wb_lat_store+0xb0/0x20c which lock already depends on the new lock. the existing dependency chain (in reverse order) is: -> #1 (&q->elevator_lock){+.+.}-{4:4}: __mutex_lock+0xf0/0xa58 ioc_qos_write+0x16c/0x85c cgroup_file_write+0xc4/0x32c kernfs_fop_write_iter+0x1b8/0x29c vfs_write+0x410/0x584 ksys_write+0x84/0x140 system_call_exception+0x134/0x360 system_call_vectored_common+0x15c/0x2ec -> #0 (&q->rq_qos_mutex){+.+.}-{4:4}: __lock_acquire+0x1b6c/0x2ae0 lock_acquire+0x140/0x430 __mutex_lock+0xf0/0xa58 wbt_init+0x164/0x238 queue_wb_lat_store+0x1dc/0x20c queue_attr_store+0x12c/0x164 sysfs_kf_write+0x6c/0xb0 kernfs_fop_write_iter+0x1b8/0x29c vfs_write+0x410/0x584 ksys_write+0x84/0x140 system_call_exception+0x134/0x360 system_call_vectored_common+0x15c/0x2ec other info that might help us debug this: Possible unsafe locking scenario: CPU0 CPU1 ---- ---- lock(&q->elevator_lock); lock(&q->rq_qos_mutex); lock(&q->elevator_lock); lock(&q->rq_qos_mutex); *** DEADLOCK *** 6 locks held by bash/5902: #0: c000000051122400 (sb_writers#3){.+.+}-{0:0}, at: ksys_write+0x84/0x140 #1: c00000007383f088 (&of->mutex#2){+.+.}-{4:4}, at: kernfs_fop_write_iter+0x174/0x29c #2: c000000008550428 (kn->active#182){.+.+}-{0:0}, at: kernfs_fop_write_iter+0x180/0x29c #3: c000000085d493a8 (&q->q_usage_counter(io)#5){++++}-{0:0}, at: blk_mq_freeze_queue_nomemsave+0x28/0x40 #4: c000000085d493e0 (&q->q_usage_counter(queue)#5){++++}-{0:0}, at: blk_mq_freeze_queue_nomemsave+0x28/0x40 #5: c000000085d498c8 (&q->elevator_lock){+.+.}-{4:4}, at: queue_wb_lat_store+0xb0/0x20c stack backtrace: CPU: 17 UID: 0 PID: 5902 Comm: bash Kdump: loaded Not tainted 6.14.0-rc5+ #138 Hardware name: IBM,9043-MRX POWER10 (architected) 0x800200 0xf000006 of:IBM,FW1060.00 (NM1060_028) hv:phyp pSeries Call Trace: [c0000000721ef590] [c00000000118f8a8] dump_stack_lvl+0x108/0x18c (unreliable) [c0000000721ef5c0] [c00000000022563c] print_circular_bug+0x448/0x604 [c0000000721ef670] [c000000000225a44] check_noncircular+0x24c/0x26c [c0000000721ef740] [c00000000022bf28] __lock_acquire+0x1b6c/0x2ae0 [c0000000721ef870] [c000000000229240] lock_acquire+0x140/0x430 [c0000000721ef970] [c0000000011cfbec] __mutex_lock+0xf0/0xa58 [c0000000721efaa0] [c00000000096c46c] wbt_init+0x164/0x238 [c0000000721efaf0] [c0000000008f8cd8] queue_wb_lat_store+0x1dc/0x20c [c0000000721efb50] [c0000000008f8fa0] queue_attr_store+0x12c/0x164 [c0000000721efc60] [c0000000007c11cc] sysfs_kf_write+0x6c/0xb0 [c0000000721efca0] [c0000000007bfa4c] kernfs_fop_write_iter+0x1b8/0x29c [c0000000721efcf0] [c0000000006a281c] vfs_write+0x410/0x584 [c0000000721efdc0] [c0000000006a2cc8] ksys_write+0x84/0x140 [c0000000721efe10] [c000000000031b64] system_call_exception+0x134/0x360 [c0000000721efe50] [c00000000000cedc] system_call_vectored_common+0x15c/0x2ec >From the above log it's apparent that method which writes to sysfs attr wbt_lat_usec acquires q->elevator_lock first, and then acquires q->rq_ qos_mutex. However the another method which writes to io.cost.qos, acquires q->rq_qos_mutex first, and then acquires q->rq_qos_mutex. So this could potentially cause the deadlock. A closer look at ioc_qos_write shows that correcting the lock order is non-trivial because q->rq_qos_mutex is acquired in blkg_conf_open_bdev and released in blkg_conf_exit. The function blkg_conf_open_bdev is responsible for parsing user input and finding the corresponding block device (bdev) from the user provided major:minor number. Since we do not know the bdev until blkg_conf_open_bdev completes, we cannot simply move q->elevator_lock acquisition before blkg_conf_open_ bdev. So to address this, we intoduce new helpers blkg_conf_open_bdev_ frozen and blkg_conf_exit_frozen which are just wrappers around blkg_ conf_open_bdev and blkg_conf_exit respectively. The helper blkg_conf_ open_bdev_frozen is similar to blkg_conf_open_bdev, but additionally freezes the queue, acquires q->elevator_lock and ensures the correct locking order is followed between q->elevator_lock and q->rq_qos_mutex. Similarly another helper blkg_conf_exit_frozen in addition to unfreezing the queue ensures that we release the locks in correct order. By using these helpers, now we maintain the same locking order in all code paths where we update blk-wbt parameters. Fixes: 245618f8e45f ("block: protect wbt_lat_usec using q->elevator_lock") Reported-by: kernel test robot <oliver.sang@intel.com> Closes: https://lore.kernel.org/oe-lkp/202503171650.cc082b66-lkp@intel.com Signed-off-by: Nilay Shroff <nilay@linux.ibm.com> Link: https://lore.kernel.org/r/20250319105518.468941-3-nilay@linux.ibm.com Signed-off-by: Jens Axboe <axboe@kernel.dk>
2025-03-18blk-cgroup: improve policy registration error handlingChen Linxuan1-10/+12
This patch improve the returned error code of blkcg_policy_register(). 1. Move the validation check for cpd/pd_alloc_fn and cpd/pd_free_fn function pairs to the start of blkcg_policy_register(). This ensures we immediately return -EINVAL if the function pairs are not correctly provided, rather than returning -ENOSPC after locking and unlocking mutexes unnecessarily. Those locks should not contention any problems, as error of policy registration is a super cold path. 2. Return -ENOMEM when cpd_alloc_fn() failed. Co-authored-by: Wen Tao <wentao@uniontech.com> Signed-off-by: Wen Tao <wentao@uniontech.com> Signed-off-by: Chen Linxuan <chenlinxuan@uniontech.com> Reviewed-by: Michal Koutný <mkoutny@suse.com> Acked-by: Tejun Heo <tj@kernel.org> Reviewed-by: Yu Kuai <yukuai3@huawei.com> Link: https://lore.kernel.org/r/3E333A73B6B6DFC0+20250317022924.150907-1-chenlinxuan@uniontech.com Signed-off-by: Jens Axboe <axboe@kernel.dk>
2025-03-11blk-cgroup: Simplify policy files registrationMichal Koutný1-2/+5
Use one set of files when there is no difference between default and legacy files, similar to regular subsys files registration. No functional change. Signed-off-by: Michal Koutný <mkoutny@suse.com> Acked-by: Jens Axboe <axboe@kernel.dk> Signed-off-by: Tejun Heo <tj@kernel.org>
2025-03-11cgroup/blkio: Add deprecation messages to reset_statsMichal Koutný1-0/+1
It is difficult to sync with stat updaters, stats are (should be) monotonic so users can calculate differences from a reference. Signed-off-by: Michal Koutný <mkoutny@suse.com> Acked-by: Jens Axboe <axboe@kernel.dk> Signed-off-by: Tejun Heo <tj@kernel.org>
2025-01-31Merge tag 'block-6.14-20250131' of git://git.kernel.dk/linuxLinus Torvalds1-4/+6
Pull more block updates from Jens Axboe: - MD pull request via Song: - Fix a md-cluster regression introduced - More sysfs race fixes - Mark anything inside queue freezing as not being able to do IO for memory allocations - Fix for a regression introduced in loop in this merge window - Fix for a regression in queue mapping setups introduced in this merge window - Fix for the block dio fops attempting an iov_iter revert upton getting -EIOCBQUEUED on the read side. This one is going to stable as well * tag 'block-6.14-20250131' of git://git.kernel.dk/linux: block: force noio scope in blk_mq_freeze_queue block: fix nr_hw_queue update racing with disk addition/removal block: get rid of request queue ->sysfs_dir_lock loop: don't clear LO_FLAGS_PARTSCAN on LOOP_SET_STATUS{,64} md/md-bitmap: Synchronize bitmap_get_stats() with bitmap lifetime blk-mq: create correct map for fallback case block: don't revert iter for -EIOCBQUEUED
2025-01-31block: force noio scope in blk_mq_freeze_queueChristoph Hellwig1-4/+6
When block drivers or the core block code perform allocations with a frozen queue, this could try to recurse into the block device to reclaim memory and deadlock. Thus all allocations done by a process that froze a queue need to be done without __GFP_IO and __GFP_FS. Instead of tying to track all of them down, force a noio scope as part of freezing the queue. Note that nvme is a bit of a mess here due to the non-owner freezes, and they will be addressed separately. Signed-off-by: Christoph Hellwig <hch@lst.de> Link: https://lore.kernel.org/r/20250131120352.1315351-2-hch@lst.de Signed-off-by: Jens Axboe <axboe@kernel.dk>
2025-01-10blk-cgroup: Fix class @block_class's subsystem refcount leakageZijun Hu1-0/+1
blkcg_fill_root_iostats() iterates over @block_class's devices by class_dev_iter_(init|next)(), but does not end iterating with class_dev_iter_exit(), so causes the class's subsystem refcount leakage. Fix by ending the iterating with class_dev_iter_exit(). Fixes: ef45fe470e1e ("blk-cgroup: show global disk stats in root cgroup io.stat") Reviewed-by: Michal Koutný <mkoutny@suse.com> Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org> Cc: stable@vger.kernel.org Acked-by: Tejun Heo <tj@kernel.org> Signed-off-by: Zijun Hu <quic_zijuhu@quicinc.com> Link: https://lore.kernel.org/r/20250105-class_fix-v6-2-3a2f1768d4d4@quicinc.com Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
2024-12-10blk-cgroup: Fix UAF in blkcg_unpin_online()Tejun Heo1-1/+5
blkcg_unpin_online() walks up the blkcg hierarchy putting the online pin. To walk up, it uses blkcg_parent(blkcg) but it was calling that after blkcg_destroy_blkgs(blkcg) which could free the blkcg, leading to the following UAF: ================================================================== BUG: KASAN: slab-use-after-free in blkcg_unpin_online+0x15a/0x270 Read of size 8 at addr ffff8881057678c0 by task kworker/9:1/117 CPU: 9 UID: 0 PID: 117 Comm: kworker/9:1 Not tainted 6.13.0-rc1-work-00182-gb8f52214c61a-dirty #48 Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS unknown 02/02/2022 Workqueue: cgwb_release cgwb_release_workfn Call Trace: <TASK> dump_stack_lvl+0x27/0x80 print_report+0x151/0x710 kasan_report+0xc0/0x100 blkcg_unpin_online+0x15a/0x270 cgwb_release_workfn+0x194/0x480 process_scheduled_works+0x71b/0xe20 worker_thread+0x82a/0xbd0 kthread+0x242/0x2c0 ret_from_fork+0x33/0x70 ret_from_fork_asm+0x1a/0x30 </TASK> ... Freed by task 1944: kasan_save_track+0x2b/0x70 kasan_save_free_info+0x3c/0x50 __kasan_slab_free+0x33/0x50 kfree+0x10c/0x330 css_free_rwork_fn+0xe6/0xb30 process_scheduled_works+0x71b/0xe20 worker_thread+0x82a/0xbd0 kthread+0x242/0x2c0 ret_from_fork+0x33/0x70 ret_from_fork_asm+0x1a/0x30 Note that the UAF is not easy to trigger as the free path is indirected behind a couple RCU grace periods and a work item execution. I could only trigger it with artifical msleep() injected in blkcg_unpin_online(). Fix it by reading the parent pointer before destroying the blkcg's blkg's. Signed-off-by: Tejun Heo <tj@kernel.org> Reported-by: Abagail ren <renzezhongucas@gmail.com> Suggested-by: Linus Torvalds <torvalds@linuxfoundation.org> Fixes: 4308a434e5e0 ("blkcg: don't offline parent blkcg first") Cc: stable@vger.kernel.org # v5.7+ Signed-off-by: Jens Axboe <axboe@kernel.dk>
2024-07-28blk-ioprio: remove per-disk structureYu Kuai1-8/+0
ioprio works on the blk-cgroup level, all disks in the same cgroup are the same, and the struct ioprio_blkg doesn't have anything in it. Hence register the policy is enough, because cpd_alloc/free_fn will be handled for each blk-cgroup, and there is no need to activate the policy for disk. Hence remove blk_ioprio_init/exit and ioprio_alloc/free_pd. Signed-off-by: Yu Kuai <yukuai3@huawei.com> Reviewed-by: Christoph Hellwig <hch@lst.de> Acked-by: Tejun Heo <tj@kernel.org> Reviewed-by: Bart Van Assche <bvanassche@acm.org> Link: https://lore.kernel.org/r/20240719071506.158075-4-yukuai1@huaweicloud.com Signed-off-by: Jens Axboe <axboe@kernel.dk>
2024-07-28blk-cgroup: check for pd_(alloc|free)_fn in blkcg_activate_policy()Yu Kuai1-2/+13
Currently all policies implement pd_(alloc|free)_fn, however, this is not necessary for ioprio that only works for blkcg, not blkg. There are no functional changes, prepare to cleanup activating ioprio policy. Signed-off-by: Yu Kuai <yukuai3@huawei.com> Reviewed-by: Christoph Hellwig <hch@lst.de> Acked-by: Tejun Heo <tj@kernel.org> Link: https://lore.kernel.org/r/20240719071506.158075-2-yukuai1@huaweicloud.com Signed-off-by: Jens Axboe <axboe@kernel.dk>
2024-07-19blk-cgroup: move congestion_count to struct blkcgXiu Jianfeng1-3/+4
The congestion_count was introduced into the struct cgroup by commit d09d8df3a294 ("blkcg: add generic throttling mechanism"), but since it is closely related to the blkio subsys, it is not appropriate to put it in the struct cgroup, so let's move it to struct blkcg. There should be no functional changes because blkcg is per cgroup. Signed-off-by: Xiu Jianfeng <xiujianfeng@huawei.com> Acked-by: Tejun Heo <tj@kernel.org> Link: https://lore.kernel.org/r/20240716133058.3491350-1-xiujianfeng@huawei.com Signed-off-by: Jens Axboe <axboe@kernel.dk>
2024-05-15blk-cgroup: Properly propagate the iostat update up the hierarchyWaiman Long1-1/+18
During a cgroup_rstat_flush() call, the lowest level of nodes are flushed first before their parents. Since commit 3b8cc6298724 ("blk-cgroup: Optimize blkcg_rstat_flush()"), iostat propagation was still done to the parent. Grandparent, however, may not get the iostat update if the parent has no blkg_iostat_set queued in its lhead lockless list. Fix this iostat propagation problem by queuing the parent's global blkg->iostat into one of its percpu lockless lists to make sure that the delta will always be propagated up to the grandparent and so on toward the root blkcg. Note that successive calls to __blkcg_rstat_flush() are serialized by the cgroup_rstat_lock. So no special barrier is used in the reading and writing of blkg->iostat.lqueued. Fixes: 3b8cc6298724 ("blk-cgroup: Optimize blkcg_rstat_flush()") Reported-by: Dan Schatzberg <schatzberg.dan@gmail.com> Closes: https://lore.kernel.org/lkml/ZkO6l%2FODzadSgdhC@dschatzberg-fedora-PF3DHTBV/ Signed-off-by: Waiman Long <longman@redhat.com> Reviewed-by: Ming Lei <ming.lei@redhat.com> Acked-by: Tejun Heo <tj@kernel.org> Link: https://lore.kernel.org/r/20240515143059.276677-1-longman@redhat.com Signed-off-by: Jens Axboe <axboe@kernel.dk>
2024-05-15blk-cgroup: fix list corruption from reorder of WRITE ->lqueuedMing Lei1-0/+10
__blkcg_rstat_flush() can be run anytime, especially when blk_cgroup_bio_start is being executed. If WRITE of `->lqueued` is re-ordered with READ of 'bisc->lnode.next' in the loop of __blkcg_rstat_flush(), `next_bisc` can be assigned with one stat instance being added in blk_cgroup_bio_start(), then the local list in __blkcg_rstat_flush() could be corrupted. Fix the issue by adding one barrier. Cc: Tejun Heo <tj@kernel.org> Cc: Waiman Long <longman@redhat.com> Fixes: 3b8cc6298724 ("blk-cgroup: Optimize blkcg_rstat_flush()") Signed-off-by: Ming Lei <ming.lei@redhat.com> Link: https://lore.kernel.org/r/20240515013157.443672-3-ming.lei@redhat.com Signed-off-by: Jens Axboe <axboe@kernel.dk>
2024-05-15blk-cgroup: fix list corruption from resetting io statMing Lei1-23/+35
Since commit 3b8cc6298724 ("blk-cgroup: Optimize blkcg_rstat_flush()"), each iostat instance is added to blkcg percpu list, so blkcg_reset_stats() can't reset the stat instance by memset(), otherwise the llist may be corrupted. Fix the issue by only resetting the counter part. Cc: Tejun Heo <tj@kernel.org> Cc: Waiman Long <longman@redhat.com> Cc: Jay Shin <jaeshin@redhat.com> Fixes: 3b8cc6298724 ("blk-cgroup: Optimize blkcg_rstat_flush()") Signed-off-by: Ming Lei <ming.lei@redhat.com> Acked-by: Tejun Heo <tj@kernel.org> Reviewed-by: Waiman Long <longman@redhat.com> Link: https://lore.kernel.org/r/20240515013157.443672-2-ming.lei@redhat.com Signed-off-by: Jens Axboe <axboe@kernel.dk>
2024-05-13Merge tag 'for-6.10/block-20240511' of git://git.kernel.dk/linuxLinus Torvalds1-8/+1
Pull block updates from Jens Axboe: - Add a partscan attribute in sysfs, fixing an issue with systemd relying on an internal interface that went away. - Attempt #2 at making long running discards interruptible. The previous attempt went into 6.9, but we ended up mostly reverting it as it had issues. - Remove old ida_simple API in bcache - Support for zoned write plugging, greatly improving the performance on zoned devices. - Remove the old throttle low interface, which has been experimental since 2017 and never made it beyond that and isn't being used. - Remove page->index debugging checks in brd, as it hasn't caught anything and prepares us for removing in struct page. - MD pull request from Song - Don't schedule block workers on isolated CPUs * tag 'for-6.10/block-20240511' of git://git.kernel.dk/linux: (84 commits) blk-throttle: delay initialization until configuration blk-throttle: remove CONFIG_BLK_DEV_THROTTLING_LOW block: fix that util can be greater than 100% block: support to account io_ticks precisely block: add plug while submitting IO bcache: fix variable length array abuse in btree_iter bcache: Remove usage of the deprecated ida_simple_xx() API md: Revert "md: Fix overflow in is_mddev_idle" blk-lib: check for kill signal in ioctl BLKDISCARD block: add a bio_await_chain helper block: add a blk_alloc_discard_bio helper block: add a bio_chain_and_submit helper block: move discard checks into the ioctl handler block: remove the discard_granularity check in __blkdev_issue_discard block/ioctl: prefer different overflow check null_blk: Fix the WARNING: modpost: missing MODULE_DESCRIPTION() block: fix and simplify blkdevparts= cmdline parsing block: refine the EOF check in blkdev_iomap_begin block: add a partscan sysfs attribute for disks block: add a disk_has_partscan helper ...
2024-05-09blk-throttle: delay initialization until configurationYu Kuai1-6/+0
Other cgroup policy like bfq, iocost are lazy-initialized when they are configured for the first time for the device, but blk-throttle is initialized unconditionally from blkcg_init_disk(). Delay initialization of blk-throttle as well, to save some cpu and memory overhead if it's not configured. Noted that once it's initialized, it can't be destroyed until disk removal, even if it's disabled. Signed-off-by: Yu Kuai <yukuai3@huawei.com> Link: https://lore.kernel.org/r/20240509121107.3195568-3-yukuai1@huaweicloud.com Signed-off-by: Jens Axboe <axboe@kernel.dk>
2024-04-07block: fix q->blkg_list corruption during disk rebindMing Lei1-3/+6
Multiple gendisk instances can allocated/added for single request queue in case of disk rebind. blkg may still stay in q->blkg_list when calling blkcg_init_disk() for rebind, then q->blkg_list becomes corrupted. Fix the list corruption issue by: - add blkg_init_queue() to initialize q->blkg_list & q->blkcg_mutex only - move calling blkg_init_queue() into blk_alloc_queue() The list corruption should be started since commit f1c006f1c685 ("blk-cgroup: synchronize pd_free_fn() from blkg_free_workfn() and blkcg_deactivate_policy()") which delays removing blkg from q->blkg_list into blkg_free_workfn(). Fixes: f1c006f1c685 ("blk-cgroup: synchronize pd_free_fn() from blkg_free_workfn() and blkcg_deactivate_policy()") Fixes: 1059699f87eb ("block: move blkcg initialization/destroy into disk allocation/release handler") Cc: Yu Kuai <yukuai3@huawei.com> Cc: Tejun Heo <tj@kernel.org> Signed-off-by: Ming Lei <ming.lei@redhat.com> Reviewed-by: Yu Kuai <yukuai3@huawei.com> Link: https://lore.kernel.org/r/20240407125910.4053377-1-ming.lei@redhat.com Signed-off-by: Jens Axboe <axboe@kernel.dk>
2024-04-01blk-cgroup: use bio_list_merge_initChristoph Hellwig1-2/+1
Use bio_list_merge_init instead of open coding bio_list_merge and bio_list_init. Signed-off-by: Christoph Hellwig <hch@lst.de> Reviewed-by: Johannes Thumshirn <johannes.thumshirn@wdc.com> Reviewed-by: Damien Le Moal <dlemoal@kernel.org> Link: https://lore.kernel.org/r/20240328084147.2954434-3-hch@lst.de Signed-off-by: Jens Axboe <axboe@kernel.dk>
2024-02-05block: add blk_time_get_ns() and blk_time_get() helpersJens Axboe1-1/+1
Convert any user of ktime_get_ns() to use blk_time_get_ns(), and ktime_get() to blk_time_get(), so we have a unified API for querying the current time in nanoseconds or as ktime. No functional changes intended, this patch just wraps ktime_get_ns() and ktime_get() with a block helper. Reviewed-by: Johannes Thumshirn <johannes.thumshirn@wdc.com> Signed-off-by: Jens Axboe <axboe@kernel.dk>
2024-01-15block: Correct a documentation comment in blk-cgroup.cNicky Chorley1-1/+1
Commit 99e603874366 ("blk-cgroup: pass a gendisk to the blkg allocation helpers") changed blkg_alloc() to take a struct gendisk instead of a struct request_queue, but the documentation comment still referred to q. So, update that comment to refer to disk instead and fix a typo. Signed-off-by: Nicky Chorley <ndchorley@gmail.com> Link: https://lore.kernel.org/r/20240114191056.6992-1-ndchorley@gmail.com Signed-off-by: Jens Axboe <axboe@kernel.dk>
2024-01-04blk-cgroup: don't use removal safe list iteratorsDaniel Vacek1-2/+2
Commit f1c006f1c685 moved deletion of the list blkg->q_node from blkg_destroy() to blkg_free_workfn(). Switch to using the list iterators, as we don't need removal protection anymore. Signed-off-by: Daniel Vacek <neelx@redhat.com> Acked-by: Tejun Heo <tj@kernel.org> Link: https://lore.kernel.org/r/20240104180031.148148-1-neelx@redhat.com Signed-off-by: Jens Axboe <axboe@kernel.dk>
2023-12-18block: skip cgroups for passthrough ioKundan Kumar1-0/+3
Even if BLK_CGROUP is enabled, it does not work for passthrough io. So skip setting up blkg for passthrough bio. Reduced processing gives ~5% hike in peak-performance workload. Signed-off-by: Kundan Kumar <kundan.kumar@samsung.com> Signed-off-by: Kanchan Joshi <joshi.k@samsung.com> Reviewed-by: Keith Busch <kbusch@kernel.org> Link: https://lore.kernel.org/r/20231218152722.1768-1-joshi.k@samsung.com Signed-off-by: Jens Axboe <axboe@kernel.dk>
2023-11-17blk-cgroup: bypass blkcg_deactivate_policy after destroyingMing Lei1-0/+13
blkcg_deactivate_policy() can be called after blkg_destroy_all() returns, and it isn't necessary since blkg_destroy_all has covered policy deactivation. Signed-off-by: Ming Lei <ming.lei@redhat.com> Link: https://lore.kernel.org/r/20231117023527.3188627-4-ming.lei@redhat.com Signed-off-by: Jens Axboe <axboe@kernel.dk>
2023-08-29Merge tag 'for-6.6/block-2023-08-28' of git://git.kernel.dk/linuxLinus Torvalds1-14/+18
Pull block updates from Jens Axboe: "Pretty quiet round for this release. This contains: - Add support for zoned storage to ublk (Andreas, Ming) - Series improving performance for drivers that mark themselves as needing a blocking context for issue (Bart) - Cleanup the flush logic (Chengming) - sed opal keyring support (Greg) - Fixes and improvements to the integrity support (Jinyoung) - Add some exports for bcachefs that we can hopefully delete again in the future (Kent) - deadline throttling fix (Zhiguo) - Series allowing building the kernel without buffer_head support (Christoph) - Sanitize the bio page adding flow (Christoph) - Write back cache fixes (Christoph) - MD updates via Song: - Fix perf regression for raid0 large sequential writes (Jan) - Fix split bio iostat for raid0 (David) - Various raid1 fixes (Heinz, Xueshi) - raid6test build fixes (WANG) - Deprecate bitmap file support (Christoph) - Fix deadlock with md sync thread (Yu) - Refactor md io accounting (Yu) - Various non-urgent fixes (Li, Yu, Jack) - Various fixes and cleanups (Arnd, Azeem, Chengming, Damien, Li, Ming, Nitesh, Ruan, Tejun, Thomas, Xu)" * tag 'for-6.6/block-2023-08-28' of git://git.kernel.dk/linux: (113 commits) block: use strscpy() to instead of strncpy() block: sed-opal: keyring support for SED keys block: sed-opal: Implement IOC_OPAL_REVERT_LSP block: sed-opal: Implement IOC_OPAL_DISCOVERY blk-mq: prealloc tags when increase tagset nr_hw_queues blk-mq: delete redundant tagset map update when fallback blk-mq: fix tags leak when shrink nr_hw_queues ublk: zoned: support REQ_OP_ZONE_RESET_ALL md: raid0: account for split bio in iostat accounting md/raid0: Fix performance regression for large sequential writes md/raid0: Factor out helper for mapping and submitting a bio md raid1: allow writebehind to work on any leg device set WriteMostly md/raid1: hold the barrier until handle_read_error() finishes md/raid1: free the r1bio before waiting for blocked rdev md/raid1: call free_r1bio() before allow_barrier() in raid_end_bio_io() blk-cgroup: Fix NULL deref caused by blkg_policy_data being installed before init drivers/rnbd: restore sysfs interface to rnbd-client md/raid5-cache: fix null-ptr-deref for r5l_flush_stripe_to_raid() raid6: test: only check for Altivec if building on powerpc hosts raid6: test: make sure all intermediate and artifact files are .gitignored ...
2023-08-18blk-cgroup: hold queue_lock when removing blkg->q_nodeMing Lei1-0/+2
When blkg is removed from q->blkg_list from blkg_free_workfn(), queue_lock has to be held, otherwise, all kinds of bugs(list corruption, hard lockup, ..) can be triggered from blkg_destroy_all(). Fixes: f1c006f1c685 ("blk-cgroup: synchronize pd_free_fn() from blkg_free_workfn() and blkcg_deactivate_policy()") Cc: Yu Kuai <yukuai3@huawei.com> Cc: xiaoli feng <xifeng@redhat.com> Cc: Chunyu Hu <chuhu@redhat.com> Cc: Mike Snitzer <snitzer@kernel.org> Cc: Tejun Heo <tj@kernel.org> Signed-off-by: Ming Lei <ming.lei@redhat.com> Acked-by: Tejun Heo <tj@kernel.org> Link: https://lore.kernel.org/r/20230817141751.1128970-1-ming.lei@redhat.com Signed-off-by: Jens Axboe <axboe@kernel.dk>
2023-08-17blk-cgroup: Fix NULL deref caused by blkg_policy_data being installed before ↵Tejun Heo1-14/+18
init blk-iocost sometimes causes the following crash: BUG: kernel NULL pointer dereference, address: 00000000000000e0 ... RIP: 0010:_raw_spin_lock+0x17/0x30 Code: be 01 02 00 00 e8 79 38 39 ff 31 d2 89 d0 5d c3 0f 1f 00 0f 1f 44 00 00 55 48 89 e5 65 ff 05 48 d0 34 7e b9 01 00 00 00 31 c0 <f0> 0f b1 0f 75 02 5d c3 89 c6 e8 ea 04 00 00 5d c3 0f 1f 84 00 00 RSP: 0018:ffffc900023b3d40 EFLAGS: 00010046 RAX: 0000000000000000 RBX: 00000000000000e0 RCX: 0000000000000001 RDX: ffffc900023b3d20 RSI: ffffc900023b3cf0 RDI: 00000000000000e0 RBP: ffffc900023b3d40 R08: ffffc900023b3c10 R09: 0000000000000003 R10: 0000000000000064 R11: 000000000000000a R12: ffff888102337000 R13: fffffffffffffff2 R14: ffff88810af408c8 R15: ffff8881070c3600 FS: 00007faaaf364fc0(0000) GS:ffff88842fdc0000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 00000000000000e0 CR3: 00000001097b1000 CR4: 0000000000350ea0 Call Trace: <TASK> ioc_weight_write+0x13d/0x410 cgroup_file_write+0x7a/0x130 kernfs_fop_write_iter+0xf5/0x170 vfs_write+0x298/0x370 ksys_write+0x5f/0xb0 __x64_sys_write+0x1b/0x20 do_syscall_64+0x3d/0x80 entry_SYSCALL_64_after_hwframe+0x46/0xb0 This happens because iocg->ioc is NULL. The field is initialized by ioc_pd_init() and never cleared. The NULL deref is caused by blkcg_activate_policy() installing blkg_policy_data before initializing it. blkcg_activate_policy() was doing the following: 1. Allocate pd's for all existing blkg's and install them in blkg->pd[]. 2. Initialize all pd's. 3. Online all pd's. blkcg_activate_policy() only grabs the queue_lock and may release and re-acquire the lock as allocation may need to sleep. ioc_weight_write() grabs blkcg->lock and iterates all its blkg's. The two can race and if ioc_weight_write() runs during #1 or between #1 and #2, it can encounter a pd which is not initialized yet, leading to crash. The crash can be reproduced with the following script: #!/bin/bash echo +io > /sys/fs/cgroup/cgroup.subtree_control systemd-run --unit touch-sda --scope dd if=/dev/sda of=/dev/null bs=1M count=1 iflag=direct echo 100 > /sys/fs/cgroup/system.slice/io.weight bash -c "echo '8:0 enable=1' > /sys/fs/cgroup/io.cost.qos" & sleep .2 echo 100 > /sys/fs/cgroup/system.slice/io.weight with the following patch applied: > diff --git a/block/blk-cgroup.c b/block/blk-cgroup.c > index fc49be622e05..38d671d5e10c 100644 > --- a/block/blk-cgroup.c > +++ b/block/blk-cgroup.c > @@ -1553,6 +1553,12 @@ int blkcg_activate_policy(struct gendisk *disk, const struct blkcg_policy *pol) > pd->online = false; > } > > + if (system_state == SYSTEM_RUNNING) { > + spin_unlock_irq(&q->queue_lock); > + ssleep(1); > + spin_lock_irq(&q->queue_lock); > + } > + > /* all allocated, init in the same order */ > if (pol->pd_init_fn) > list_for_each_entry_reverse(blkg, &q->blkg_list, q_node) I don't see a reason why all pd's should be allocated, initialized and onlined together. The only ordering requirement is that parent blkgs to be initialized and onlined before children, which is guaranteed from the walking order. Let's fix the bug by allocating, initializing and onlining pd for each blkg and holding blkcg->lock over initialization and onlining. This ensures that an installed blkg is always fully initialized and onlined removing the the race window. Signed-off-by: Tejun Heo <tj@kernel.org> Reported-by: Breno Leitao <leitao@debian.org> Fixes: 9d179b865449 ("blkcg: Fix multiple bugs in blkcg_activate_policy()") Link: https://lore.kernel.org/r/ZN0p5_W-Q9mAHBVY@slm.duckdns.org Signed-off-by: Jens Axboe <axboe@kernel.dk>
2023-06-28Merge branch 'for-6.5/block-late' into block-6.5Jens Axboe1-2/+4
* for-6.5/block-late: blk-sysfs: add a new attr_group for blk_mq blk-iocost: move wbt_enable/disable_default() out of spinlock blk-wbt: cleanup rwb_enabled() and wbt_disabled() blk-wbt: remove dead code to handle wbt enable/disable with io inflight blk-wbt: don't create wbt sysfs entry if CONFIG_BLK_WBT is disabled blk-mq: fix two misuses on RQF_USE_SCHED blk-throttle: Fix io statistics for cgroup v1 bcache: Fix bcache device claiming bcache: Alloc holder object before async registration raid10: avoid spin_lock from fastpath from raid10_unplug() md: fix 'delete_mutex' deadlock md: use mddev->external to select holder in export_rdev() md/raid1-10: fix casting from randomized structure in raid1_submit_write() md/raid10: fix the condition to call bio_end_io_acct()
2023-06-26Merge tag 'for-6.5/block-2023-06-23' of git://git.kernel.dk/linuxLinus Torvalds1-0/+14
Pull block updates from Jens Axboe: - NVMe pull request via Keith: - Various cleanups all around (Irvin, Chaitanya, Christophe) - Better struct packing (Christophe JAILLET) - Reduce controller error logs for optional commands (Keith) - Support for >=64KiB block sizes (Daniel Gomez) - Fabrics fixes and code organization (Max, Chaitanya, Daniel Wagner) - bcache updates via Coly: - Fix a race at init time (Mingzhe Zou) - Misc fixes and cleanups (Andrea, Thomas, Zheng, Ye) - use page pinning in the block layer for dio (David) - convert old block dio code to page pinning (David, Christoph) - cleanups for pktcdvd (Andy) - cleanups for rnbd (Guoqing) - use the unchecked __bio_add_page() for the initial single page additions (Johannes) - fix overflows in the Amiga partition handling code (Michael) - improve mq-deadline zoned device support (Bart) - keep passthrough requests out of the IO schedulers (Christoph, Ming) - improve support for flush requests, making them less special to deal with (Christoph) - add bdev holder ops and shutdown methods (Christoph) - fix the name_to_dev_t() situation and use cases (Christoph) - decouple the block open flags from fmode_t (Christoph) - ublk updates and cleanups, including adding user copy support (Ming) - BFQ sanity checking (Bart) - convert brd from radix to xarray (Pankaj) - constify various structures (Thomas, Ivan) - more fine grained persistent reservation ioctl capability checks (Jingbo) - misc fixes and cleanups (Arnd, Azeem, Demi, Ed, Hengqi, Hou, Jan, Jordy, Li, Min, Yu, Zhong, Waiman) * tag 'for-6.5/block-2023-06-23' of git://git.kernel.dk/linux: (266 commits) scsi/sg: don't grab scsi host module reference ext4: Fix warning in blkdev_put() block: don't return -EINVAL for not found names in devt_from_devname cdrom: Fix spectre-v1 gadget block: Improve kernel-doc headers blk-mq: don't insert passthrough request into sw queue bsg: make bsg_class a static const structure ublk: make ublk_chr_class a static const structure aoe: make aoe_class a static const structure block/rnbd: make all 'class' structures const block: fix the exclusive open mask in disk_scan_partitions block: add overflow checks for Amiga partition support block: change all __u32 annotations to __be32 in affs_hardblocks.h block: fix signed int overflow in Amiga partition support block: add capacity validation in bdev_add_partition() block: fine-granular CAP_SYS_ADMIN for Persistent Reservation block: disallow Persistent Reservation on partitions reiserfs: fix blkdev_put() warning from release_journal_dev() block: fix wrong mode for blkdev_get_by_dev() from disk_scan_partitions() block: document the holder argument to blkdev_get_by_path ...
2023-06-25blk-throttle: Fix io statistics for cgroup v1Jinke Han1-2/+4
After commit f382fb0bcef4 ("block: remove legacy IO schedulers"), blkio.throttle.io_serviced and blkio.throttle.io_service_bytes become the only stable io stats interface of cgroup v1, and these statistics are done in the blk-throttle code. But the current code only counts the bios that are actually throttled. When the user does not add the throttle limit, the io stats for cgroup v1 has nothing. I fix it according to the statistical method of v2, and made it count all ios accurately. Fixes: a7b36ee6ba29 ("block: move blk-throtl fast path inline") Tested-by: Andrea Righi <andrea.righi@canonical.com> Signed-off-by: Jinke Han <hanjinke.666@bytedance.com> Acked-by: Muchun Song <songmuchun@bytedance.com> Acked-by: Tejun Heo <tj@kernel.org> Link: https://lore.kernel.org/r/20230507170631.89607-1-hanjinke.666@bytedance.com Signed-off-by: Jens Axboe <axboe@kernel.dk>
2023-06-22block: make sure local irq is disabled when calling __blkcg_rstat_flushMing Lei1-2/+3
When __blkcg_rstat_flush() is called from cgroup_rstat_flush*() code path, interrupt is always disabled. When we start to flush blkcg per-cpu stats list in __blkg_release() for avoiding to leak blkcg_gq's reference in commit 20cb1c2fb756 ("blk-cgroup: Flush stats before releasing blkcg_gq"), local irq isn't disabled yet, then lockdep warning may be triggered because the dependent cgroup locks may be acquired from irq(soft irq) handler. Fix the issue by disabling local irq always. Fixes: 20cb1c2fb756 ("blk-cgroup: Flush stats before releasing blkcg_gq") Reported-by: Shinichiro Kawasaki <shinichiro.kawasaki@wdc.com> Closes: https://lore.kernel.org/linux-block/pz2wzwnmn5tk3pwpskmjhli6g3qly7eoknilb26of376c7kwxy@qydzpvt6zpis/T/#u Cc: stable@vger.kernel.org Cc: Jay Shin <jaeshin@redhat.com> Cc: Tejun Heo <tj@kernel.org> Cc: Waiman Long <longman@redhat.com> Signed-off-by: Ming Lei <ming.lei@redhat.com> Reviewed-by: Waiman Long <longman@redhat.com> Link: https://lore.kernel.org/r/20230622084249.1208005-1-ming.lei@redhat.com Signed-off-by: Jens Axboe <axboe@kernel.dk>
2023-06-11blk-cgroup: Flush stats before releasing blkcg_gqMing Lei1-9/+31
As noted by Michal, the blkg_iostat_set's in the lockless list hold reference to blkg's to protect against their removal. Those blkg's hold reference to blkcg. When a cgroup is being destroyed, cgroup_rstat_flush() is only called at css_release_work_fn() which is called when the blkcg reference count reaches 0. This circular dependency will prevent blkcg and some blkgs from being freed after they are made offline. It is less a problem if the cgroup to be destroyed also has other controllers like memory that will call cgroup_rstat_flush() which will clean up the reference count. If block is the only controller that uses rstat, these offline blkcg and blkgs may never be freed leaking more and more memory over time. To prevent this potential memory leak: - flush blkcg per-cpu stats list in __blkg_release(), when no new stat can be added - add global blkg_stat_lock for covering concurrent parent blkg stat update - don't grab bio->bi_blkg reference when adding the stats into blkcg's per-cpu stat list since all stats are guaranteed to be consumed before releasing blkg instance, and grabbing blkg reference for stats was the most fragile part of original patch Based on Waiman's patch: https://lore.kernel.org/linux-block/20221215033132.230023-3-longman@redhat.com/ Fixes: 3b8cc6298724 ("blk-cgroup: Optimize blkcg_rstat_flush()") Cc: stable@vger.kernel.org Reported-by: Jay Shin <jaeshin@redhat.com> Acked-by: Tejun Heo <tj@kernel.org> Cc: Waiman Long <longman@redhat.com> Cc: mkoutny@suse.com Cc: Yosry Ahmed <yosryahmed@google.com> Signed-off-by: Ming Lei <ming.lei@redhat.com> Link: https://lore.kernel.org/r/20230609234249.1412858-1-ming.lei@redhat.com Signed-off-by: Jens Axboe <axboe@kernel.dk>
2023-06-07blk-cgroup: Reinit blkg_iostat_set after clearing in blkcg_reset_stats()Waiman Long1-0/+5
When blkg_alloc() is called to allocate a blkcg_gq structure with the associated blkg_iostat_set's, there are 2 fields within blkg_iostat_set that requires proper initialization - blkg & sync. The former field was introduced by commit 3b8cc6298724 ("blk-cgroup: Optimize blkcg_rstat_flush()") while the later one was introduced by commit f73316482977 ("blk-cgroup: reimplement basic IO stats using cgroup rstat"). Unfortunately those fields in the blkg_iostat_set's are not properly re-initialized when they are cleared in v1's blkcg_reset_stats(). This can lead to a kernel panic due to NULL pointer access of the blkg pointer. The missing initialization of sync is less problematic and can be a problem in a debug kernel due to missing lockdep initialization. Fix these problems by re-initializing them after memory clearing. Fixes: 3b8cc6298724 ("blk-cgroup: Optimize blkcg_rstat_flush()") Fixes: f73316482977 ("blk-cgroup: reimplement basic IO stats using cgroup rstat") Signed-off-by: Waiman Long <longman@redhat.com> Reviewed-by: Ming Lei <ming.lei@redhat.com> Acked-by: Tejun Heo <tj@kernel.org> Link: https://lore.kernel.org/r/20230606180724.2455066-1-longman@redhat.com Signed-off-by: Jens Axboe <axboe@kernel.dk>
2023-05-23block/rq_qos: protect rq_qos apis with a new lockYu Kuai1-0/+9
commit 50e34d78815e ("block: disable the elevator int del_gendisk") move rq_qos_exit() from disk_release() to del_gendisk(), this will introduce some problems: 1) If rq_qos_add() is triggered by enabling iocost/iolatency through cgroupfs, then it can concurrent with del_gendisk(), it's not safe to write 'q->rq_qos' concurrently. 2) Activate cgroup policy that is relied on rq_qos will call rq_qos_add() and blkcg_activate_policy(), and if rq_qos_exit() is called in the middle, null-ptr-dereference will be triggered in blkcg_activate_policy(). 3) blkg_conf_open_bdev() can call blkdev_get_no_open() first to find the disk, then if rq_qos_exit() from del_gendisk() is done before rq_qos_add(), then memory will be leaked. This patch add a new disk level mutex 'rq_qos_mutex': 1) The lock will protect rq_qos_exit() directly. 2) For wbt that doesn't relied on blk-cgroup, rq_qos_add() can only be called from disk initialization for now because wbt can't be destructed until rq_qos_exit(), so it's safe not to protect wbt for now. Hoever, in case that rq_qos dynamically destruc