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2020-09-01blk-iocost: implement Andy's method for donation weight updatesTejun Heo1-8/+244
iocost implements work conservation by reducing iocg->inuse and propagating the adjustment upwards proportionally. However, while I knew the target absolute hierarchical proportion - adjusted hweight_inuse, I couldn't figure out how to determine the iocg->inuse adjustment to achieve that and approximated the adjustment by scaling iocg->inuse using the proportion of the needed hweight_inuse changes. When nested, these scalings aren't accurate even when adjusting a single node as the donating node also receives the benefit of the donated portion. When multiple nodes are donating as they often do, they can be wildly wrong. iocost employed various safety nets to combat the inaccuracies. There are ample buffers in determining how much to donate, the adjustments are conservative and gradual. While it can achieve a reasonable level of work conservation in simple scenarios, the inaccuracies can easily add up leading to significant loss of total work. This in turn makes it difficult to closely cap vrate as vrate adjustment is needed to compensate for the loss of work. The combination of inaccurate donation calculations and vrate adjustments can lead to wide fluctuations and clunky overall behaviors. Andy Newell devised a method to calculate the needed ->inuse updates to achieve the target hweight_inuse's. The method is compatible with the proportional inuse adjustment propagation which allows all hot path operations to be local to each iocg. To roughly summarize, Andy's method divides the tree into donating and non-donating parts, calculates global donation rate which is used to determine the target hweight_inuse for each node, and then derives per-level proportions. There's non-trivial amount of math involved. Please refer to the following pdfs for detailed descriptions. https://drive.google.com/file/d/1PsJwxPFtjUnwOY1QJ5AeICCcsL7BM3bo https://drive.google.com/file/d/1vONz1-fzVO7oY5DXXsLjSxEtYYQbOvsE https://drive.google.com/file/d/1WcrltBOSPN0qXVdBgnKm4mdp9FhuEFQN This patch implements Andy's method in transfer_surpluses(). This makes the donation calculations accurate per cycle and enables further improvements in other parts of the donation logic. Signed-off-by: Tejun Heo <tj@kernel.org> Cc: Andy Newell <newella@fb.com> Signed-off-by: Jens Axboe <axboe@kernel.dk>
2020-09-01blk-iocost: restructure surplus donation logicTejun Heo1-76/+103
The way the surplus donation logic is structured isn't great. There are two separate paths for starting/increasing donations and decreasing them making the logic harder to follow and is prone to unnecessary behavior differences. In preparation for improved donation handling, this patch restructures the code so that * All donors - new, increasing and decreasing - are funneled through the same code path. * The target donation calculation is factored into hweight_after_donation() which is called once from the same spot for all possible donors. * Actual inuse adjustment is factored into trasnfer_surpluses(). This change introduces a few behavior differences - e.g. donation amount reduction now uses the max usage of the recent three periods just like new and increasing donations, and inuse now gets adjusted upwards the same way it gets downwards. These differences are unlikely to have severely negative implications and the whole logic will be revamped soon. This patch also removes two tracepoints. The existing TPs don't quite fit the new implementation. A later patch will update and reinstate them. Signed-off-by: Tejun Heo <tj@kernel.org> Signed-off-by: Jens Axboe <axboe@kernel.dk>
2020-09-01blk-iocost: decouple vrate adjustment from surplus transfersTejun Heo1-12/+7
Budget donations are inaccurate and could take multiple periods to converge. To prevent triggering vrate adjustments while surplus transfers were catching up, vrate adjustment was suppressed if donations were increasing, which was indicated by non-zero nr_surpluses. This entangling won't be necessary with the scheduled rewrite of donation mechanism which will make it precise and immediate. Let's decouple the two in preparation. Signed-off-by: Tejun Heo <tj@kernel.org> Signed-off-by: Jens Axboe <axboe@kernel.dk>
2020-09-01blk-iocost: replace iocg->has_surplus with ->surplus_listTejun Heo1-8/+11
Instead of marking iocgs with surplus with a flag and filtering for them while walking all active iocgs, build a surpluses list. This doesn't make much difference now but will help implementing improved donation logic which will iterate iocgs with surplus multiple times. Signed-off-by: Tejun Heo <tj@kernel.org> Signed-off-by: Jens Axboe <axboe@kernel.dk>
2020-09-01blk-iocost: calculate iocg->usages[] from iocg->local_stat.usage_usTejun Heo1-27/+45
Currently, iocg->usages[] which are used to guide inuse adjustments are calculated from vtime deltas. This, however, assumes that the hierarchical inuse weight at the time of calculation held for the entire period, which often isn't true and can lead to significant errors. Now that we have absolute usage information collected, we can derive iocg->usages[] from iocg->local_stat.usage_us so that inuse adjustment decisions are made based on actual absolute usage. The calculated usage is clamped between 1 and WEIGHT_ONE and WEIGHT_ONE is also used to signal saturation regardless of the current hierarchical inuse weight. Signed-off-by: Tejun Heo <tj@kernel.org> Signed-off-by: Jens Axboe <axboe@kernel.dk>
2020-09-01blk-iocost: add absolute usage statTejun Heo1-6/+149
Currently, iocost doesn't collect or expose any statistics punting off all monitoring duties to drgn based iocost_monitor.py. While it works for some scenarios, there are some usability and data availability challenges. For example, accurate per-cgroup usage information can't be tracked by vtime progression at all and the number available in iocg->usages[] are really short-term snapshots used for control heuristics with possibly significant errors. This patch implements per-cgroup absolute usage stat counter and exposes it through io.stat along with the current vrate. Usage stat collection and flushing employ the same method as cgroup rstat on the active iocg's and the only hot path overhead is preemption toggling and adding to a percpu counter. Signed-off-by: Tejun Heo <tj@kernel.org> Signed-off-by: Jens Axboe <axboe@kernel.dk>
2020-09-01blk-iocost: grab ioc->lock for debt handlingTejun Heo1-19/+73
Currently, debt handling requires only iocg->waitq.lock. In the future, we want to adjust and propagate inuse changes depending on debt status. Let's grab ioc->lock in debt handling paths in preparation. * Because ioc->lock nests outside iocg->waitq.lock, the decision to grab ioc->lock needs to be made before entering the critical sections. * Add and use iocg_[un]lock() which handles the conditional double locking. * Add @pay_debt to iocg_kick_waitq() so that debt payment happens only when the caller grabbed both locks. This patch is prepatory and the comments contain references to future changes. Signed-off-by: Tejun Heo <tj@kernel.org> Signed-off-by: Jens Axboe <axboe@kernel.dk>
2020-09-01blk-iocost: streamline vtime margin and timer slack handlingTejun Heo1-29/+38
The margin handling was pretty inconsistent. * ioc->margin_us and ioc->inuse_margin_vtime were used as vtime margin thresholds. However, the two are in different units with the former requiring conversion to vtime on use. * iocg_kick_waitq() was using a quarter of WAITQ_TIMER_MARGIN_PCT of period_us as the timer slack - ~1.2%. While iocg_kick_delay() was using a quarter of ioc->margin_us - ~12.5%. There aren't strong reasons to use different values for the two. This patch cleans up margin and timer slack handling: * vtime margins are now recorded in ioc->margins.{min, max} on period duration changes and used consistently. * Timer slack is now 1% of period_us and recorded in ioc->timer_slack_ns and used consistently for iocg_kick_waitq() and iocg_kick_delay(). The only functional change is shortening of timer slack. No meaningful visible change is expected. Signed-off-by: Tejun Heo <tj@kernel.org> Signed-off-by: Jens Axboe <axboe@kernel.dk>
2020-09-01blk-iocost: make ioc_now->now and ioc->period_at 64bitTejun Heo1-2/+2
They are in microseconds and wrap in around 1.2 hours with u32. While unlikely, confusions from wraparounds are still possible. We aren't saving anything meaningful by keeping these u32. Let's make them u64. Signed-off-by: Tejun Heo <tj@kernel.org> Signed-off-by: Jens Axboe <axboe@kernel.dk>
2020-09-01blk-iocost: use WEIGHT_ONE based fixed point number for weightsTejun Heo1-12/+13
To improve weight donations, we want to able to scale inuse with a greater accuracy and down below 1. Let's make non-hierarchical weights to use WEIGHT_ONE based fixed point numbers too like hierarchical ones. This doesn't cause any behavior changes yet. Signed-off-by: Tejun Heo <tj@kernel.org> Signed-off-by: Jens Axboe <axboe@kernel.dk>
2020-09-01blk-iocost: s/HWEIGHT_WHOLE/WEIGHT_ONE/gTejun Heo1-10/+10
We're gonna use HWEIGHT_WHOLE for regular weights too. Let's rename it to WEIGHT_ONE. Pure rename. Signed-off-by: Tejun Heo <tj@kernel.org> Signed-off-by: Jens Axboe <axboe@kernel.dk>
2020-09-01blk-iocost: make iocg_kick_waitq() call iocg_kick_delay() after paying debtTejun Heo1-1/+2
iocg_kick_waitq() is the function which pays debt and iocg_kick_delay() updates the actual delay status accordingly. If iocg_kick_delay() is not called after iocg_kick_delay() updated debt, unnecessarily large delays can be applied temporarily. Let's make sure such conditions don't occur by making iocg_kick_waitq() always call iocg_kick_delay() after paying debt. Signed-off-by: Tejun Heo <tj@kernel.org> Signed-off-by: Jens Axboe <axboe@kernel.dk>
2020-09-01blk-iocost: move iocg_kick_delay() above iocg_kick_waitq()Tejun Heo1-60/+60
We'll make iocg_kick_waitq() call iocg_kick_delay(). Reorder them in preparation. This is pure code reorganization. Signed-off-by: Tejun Heo <tj@kernel.org> Signed-off-by: Jens Axboe <axboe@kernel.dk>
2020-09-01blk-iocost: clamp inuse and skip noops in __propagate_weights()Tejun Heo1-1/+4
__propagate_weights() currently expects the callers to clamp inuse within [1, active], which is needlessly fragile. The inuse adjustment logic is going to be revamped, in preparation, let's make __propagate_weights() clamp inuse on entry. Also, make it avoid weight updates altogether if neither active or inuse is changed. Signed-off-by: Tejun Heo <tj@kernel.org> Signed-off-by: Jens Axboe <axboe@kernel.dk>
2020-09-01blk-iocost: rename propagate_active_weights() to propagate_weights()Tejun Heo1-20/+20
It already propagates two weights - active and inuse - and there will be another soon. Let's drop the confusing misnomers. Rename [__]propagate_active_weights() to [__]propagate_weights() and commit_active_weights() to commit_weights(). This is pure rename. Signed-off-by: Tejun Heo <tj@kernel.org> Signed-off-by: Jens Axboe <axboe@kernel.dk>
2020-09-01blk-iocost: use local[64]_t for percpu statTejun Heo1-10/+27
blk-iocost has been reading percpu stat counters from remote cpus which on some archs can lead to torn reads in really rare occassions. Use local[64]_t for those counters. Signed-off-by: Tejun Heo <tj@kernel.org> Signed-off-by: Jens Axboe <axboe@kernel.dk>
2020-09-01block: remove the unused q argument to part_in_flight and part_in_flight_rwChristoph Hellwig1-7/+5
Signed-off-by: Christoph Hellwig <hch@lst.de> Signed-off-by: Jens Axboe <axboe@kernel.dk>
2020-09-01block: remove the disk argument to delete_partitionChristoph Hellwig3-6/+7
We can trivially derive the gendisk from the hd_struct. Signed-off-by: Christoph Hellwig <hch@lst.de> Signed-off-by: Jens Axboe <axboe@kernel.dk>
2020-09-01block: cleanup __alloc_disk_nodeChristoph Hellwig1-35/+38
Use early returns and goto-based unwinding to simplify the flow a bit. Signed-off-by: Christoph Hellwig <hch@lst.de> Signed-off-by: Jens Axboe <axboe@kernel.dk>
2020-09-01block: remove the discard_alignment field from struct hd_structChristoph Hellwig1-3/+4
The alignment offset is only used in slow path callers, so just calculate it on the fly. Signed-off-by: Christoph Hellwig <hch@lst.de> Signed-off-by: Jens Axboe <axboe@kernel.dk>
2020-09-01block: remove the alignment_offset field from struct hd_structChristoph Hellwig1-3/+4
The alignment offset is only used in slow path callers, so just calculate it on the fly. Signed-off-by: Christoph Hellwig <hch@lst.de> Signed-off-by: Jens Axboe <axboe@kernel.dk>
2020-09-01blk-mq: use BLK_MQ_NO_TAG for no tagXianting Tian2-3/+3
Replace various magic -1 constants for tags with BLK_MQ_NO_TAG. Signed-off-by: Xianting Tian <tian.xianting@h3c.com> Signed-off-by: Jens Axboe <axboe@kernel.dk>
2020-09-01block: Remove blk_mq_attempt_merge() functionBaolin Wang1-28/+16
The small blk_mq_attempt_merge() function is only called by __blk_mq_sched_bio_merge(), just open code it. Reviewed-by: Christoph Hellwig <hch@lst.de> Signed-off-by: Baolin Wang <baolin.wang@linux.alibaba.com> Signed-off-by: Jens Axboe <axboe@kernel.dk>
2020-09-01block: Add a new helper to attempt to merge a bioBaolin Wang3-60/+71
There are lots of duplicated code when trying to merge a bio from plug list and sw queue, we can introduce a new helper to attempt to merge a bio, which can simplify the blk_bio_list_merge() and blk_attempt_plug_merge(). Reviewed-by: Christoph Hellwig <hch@lst.de> Signed-off-by: Baolin Wang <baolin.wang@linux.alibaba.com> Signed-off-by: Jens Axboe <axboe@kernel.dk>
2020-09-01block: Move blk_mq_bio_list_merge() into blk-merge.cBaolin Wang4-46/+48
Move the blk_mq_bio_list_merge() into blk-merge.c and rename it as a generic name. Reviewed-by: Christoph Hellwig <hch@lst.de> Signed-off-by: Baolin Wang <baolin.wang@linux.alibaba.com> Signed-off-by: Jens Axboe <axboe@kernel.dk>
2020-09-01block: Move bio merge related functions into blk-merge.cBaolin Wang2-156/+157
It's better to move bio merge related functions into blk-merge.c, which contains all merge related functions. Reviewed-by: Christoph Hellwig <hch@lst.de> Signed-off-by: Baolin Wang <baolin.wang@linux.alibaba.com> Signed-off-by: Jens Axboe <axboe@kernel.dk>
2020-09-01blk-wbt: Remove obsolete multiqueue I/O scheduling commentDanny Lin1-2/+0
This comment was added before the multiqueue I/O scheduler framework was introduced; multiqueue has support for I/O scheduling now, so this obsolete comment can be removed. Signed-off-by: Danny Lin <danny@kdrag0n.dev> Signed-off-by: Jens Axboe <axboe@kernel.dk>
2020-09-01block: remove the BIO_USER_MAPPED flagChristoph Hellwig1-6/+4
Just check if there is private data, in which case the bio must have originated from bio_copy_user_iov. Signed-off-by: Christoph Hellwig <hch@lst.de> Signed-off-by: Jens Axboe <axboe@kernel.dk>
2020-09-01block: remove __blk_rq_map_user_iovChristoph Hellwig1-90/+54
Just duplicate a small amount of code in the low-level map into the bio and copy to the bio routines, leading to much easier to follow and maintain code, and better shared error handling. Signed-off-by: Christoph Hellwig <hch@lst.de> Signed-off-by: Jens Axboe <axboe@kernel.dk>
2020-09-01block: remove __blk_rq_unmap_userChristoph Hellwig1-18/+11
Open code __blk_rq_unmap_user in the two callers. Both never pass a NULL bio, and one of them can use an existing local variable instead of the bio flag. Signed-off-by: Christoph Hellwig <hch@lst.de> Signed-off-by: Jens Axboe <axboe@kernel.dk>
2020-09-01block: remove the BIO_NULL_MAPPED flagChristoph Hellwig1-4/+5
We can simply use a boolean flag in the bio_map_data data structure instead. Signed-off-by: Christoph Hellwig <hch@lst.de> Signed-off-by: Jens Axboe <axboe@kernel.dk>
2020-09-01block: fix locking for struct block_device size updatesChristoph Hellwig1-2/+2
Two different callers use two different mutexes for updating the block device size, which obviously doesn't help to actually protect against concurrent updates from the different callers. In addition one of the locks, bd_mutex is rather prone to deadlocks with other parts of the block stack that use it for high level synchronization. Switch to using a new spinlock protecting just the size updates, as that is all we need, and make sure everyone does the update through the proper helper. This fixes a bug reported with the nvme revalidating disks during a hot removal operation, which can currently deadlock on bd_mutex. Reported-by: Xianting Tian <xianting_tian@126.com> Signed-off-by: Christoph Hellwig <hch@lst.de> Reviewed-by: Sagi Grimberg <sagi@grimberg.me> Signed-off-by: Jens Axboe <axboe@kernel.dk>
2020-09-01Merge branch 'block-5.9' into for-5.10/blockJens Axboe4-23/+37
* block-5.9: blk-stat: make q->stats->lock irqsafe blk-iocost: ioc_pd_free() shouldn't assume irq disabled block: fix locking in bdev_del_partition block: release disk reference in hd_struct_free_work block: ensure bdi->io_pages is always initialized nvme-pci: cancel nvme device request before disabling nvme: only use power of two io boundaries nvme: fix controller instance leak nvmet-fc: Fix a missed _irqsave version of spin_lock in 'nvmet_fc_fod_op_done()' nvme: Fix NULL dereference for pci nvme controllers nvme-rdma: fix reset hang if controller died in the middle of a reset nvme-rdma: fix timeout handler nvme-rdma: serialize controller teardown sequences nvme-tcp: fix reset hang if controller died in the middle of a reset nvme-tcp: fix timeout handler nvme-tcp: serialize controller teardown sequences nvme: have nvme_wait_freeze_timeout return if it timed out nvme-fabrics: don't check state NVME_CTRL_NEW for request acceptance nvmet-tcp: Fix NULL dereference when a connect data comes in h2cdata pdu
2020-09-01blk-stat: make q->stats->lock irqsafeTejun Heo1-6/+11
blk-iocost calls blk_stat_enable_accounting() while holding an irqsafe lock which triggers a lockdep splat because q->stats->lock isn't irqsafe. Let's make it irqsafe. Signed-off-by: Tejun Heo <tj@kernel.org> Fixes: cd006509b0a9 ("blk-iocost: account for IO size when testing latencies") Cc: stable@vger.kernel.org # v5.8+ Signed-off-by: Jens Axboe <axboe@kernel.dk>
2020-09-01blk-iocost: ioc_pd_free() shouldn't assume irq disabledTejun Heo1-2/+3
ioc_pd_free() grabs irq-safe ioc->lock without ensuring that irq is disabled when it can be called with irq disabled or enabled. This has a small chance of causing A-A deadlocks and triggers lockdep splats. Use irqsave operations instead. Signed-off-by: Tejun Heo <tj@kernel.org> Fixes: 7caa47151ab2 ("blkcg: implement blk-iocost") Cc: stable@vger.kernel.org # v5.4+ Signed-off-by: Jens Axboe <axboe@kernel.dk>
2020-09-01block: fix locking in bdev_del_partitionChristoph Hellwig1-14/+13
We need to hold the whole device bd_mutex to protect against other thread concurrently deleting out partition before we get to it, and thus causing a use after free. Fixes: cddae808aeb7 ("block: pass a hd_struct to delete_partition") Reported-by: syzbot+6448f3c229bc52b82f69@syzkaller.appspotmail.com Signed-off-by: Christoph Hellwig <hch@lst.de> Signed-off-by: Jens Axboe <axboe@kernel.dk>
2020-09-01block: release disk reference in hd_struct_free_workMing Lei1-1/+9
Commit e8c7d14ac6c3 ("block: revert back to synchronous request_queue removal") stops to release request queue from wq context because that commit supposed all blk_put_queue() is called in context which is allowed to sleep. However, this assumption isn't true because we release disk's reference in partition's percpu_ref's ->release() which doesn't allow to sleep, because the ->release() is run via call_rcu(). Fixes this issue by moving put disk reference into hd_struct_free_work() Fixes: e8c7d14ac6c3 ("block: revert back to synchronous request_queue removal") Reported-by: Ilya Dryomov <idryomov@gmail.com> Signed-off-by: Ming Lei <ming.lei@redhat.com> Tested-by: Ilya Dryomov <idryomov@gmail.com> Reviewed-by: Christoph Hellwig <hch@lst.de> Cc: Luis Chamberlain <mcgrof@kernel.org> Cc: Christoph Hellwig <hch@lst.de> Cc: Bart Van Assche <bvanassche@acm.org> Signed-off-by: Jens Axboe <axboe@kernel.dk>
2020-09-01block: ensure bdi->io_pages is always initializedJens Axboe1-0/+1
If a driver leaves the limit settings as the defaults, then we don't initialize bdi->io_pages. This means that file systems may need to work around bdi->io_pages == 0, which is somewhat messy. Initialize the default value just like we do for ->ra_pages. Cc: stable@vger.kernel.org Fixes: 9491ae4aade6 ("mm: don't cap request size based on read-ahead setting") Reported-by: OGAWA Hirofumi <hirofumi@mail.parknet.co.jp> Reviewed-by: Christoph Hellwig <hch@lst.de> Signed-off-by: Jens Axboe <axboe@kernel.dk>
2020-08-24Merge tag 'io_uring-5.9-2020-08-23' of git://git.kernel.dk/linux-blockLinus Torvalds9-25/+45
Pull block fixes from Jens Axboe: - NVMe pull request from Sagi: - nvme completion rework from Christoph and Chao that mostly came from a bit of divergence of how we classify errors related to pathing/retry etc. - nvmet passthru fixes from Chaitanya - minor nvmet fixes from Amit and I - mpath round-robin path selection fix from Martin - ignore noiob for zoned devices from Keith - minor nvme-fc fix from Tianjia" - BFQ cgroup leak fix (Dmitry) - block layer MAINTAINERS addition (Geert) - fix null_blk FUA checking (Hou) - get_max_io_size() size fix (Keith) - fix block page_is_mergeable() for compound pages (Matthew) - discard granularity fixes (Ming) - IO scheduler ordering fix (Ming) - misc fixes * tag 'io_uring-5.9-2020-08-23' of git://git.kernel.dk/linux-block: (31 commits) null_blk: fix passing of REQ_FUA flag in null_handle_rq nvmet: Disable keep-alive timer when kato is cleared to 0h nvme: redirect commands on dying queue nvme: just check the status code type in nvme_is_path_error nvme: refactor command completion nvme: rename and document nvme_end_request nvme: skip noiob for zoned devices nvme-pci: fix PRP pool size nvme-pci: Use u32 for nvme_dev.q_depth and nvme_queue.q_depth nvme: Use spin_lock_irq() when taking the ctrl->lock nvmet: call blk_mq_free_request() directly nvmet: fix oops in pt cmd execution nvmet: add ns tear down label for pt-cmd handling nvme: multipath: round-robin: eliminate "fallback" variable nvme: multipath: round-robin: fix single non-optimized path case nvme-fc: Fix wrong return value in __nvme_fc_init_request() nvmet-passthru: Reject commands with non-sgl flags set nvmet: fix a memory leak blkcg: fix memleak for iolatency MAINTAINERS: Add missing header files to BLOCK LAYER section ...
2020-08-23treewide: Use fallthrough pseudo-keywordGustavo A. R. Silva4-5/+5
Replace the existing /* fall through */ comments and its variants with the new pseudo-keyword macro fallthrough[1]. Also, remove unnecessary fall-through markings when it is the case. [1] https://www.kernel.org/doc/html/v5.7/process/deprecated.html?highlight=fallthrough#implicit-switch-case-fall-through Signed-off-by: Gustavo A. R. Silva <gustavoars@kernel.org>
2020-08-21blkcg: fix memleak for iolatencyYufen Yu1-3/+5
Normally, blkcg_iolatency_exit() will free related memory in iolatency when cleanup queue. But if blk_throtl_init() return error and queue init fail, blkcg_iolatency_exit() will not do that for us. Then it cause memory leak. Fixes: d70675121546 ("block: introduce blk-iolatency io controller") Signed-off-by: Yufen Yu <yuyufen@huawei.com> Signed-off-by: Jens Axboe <axboe@kernel.dk>
2020-08-21block: fix get_max_io_size()Keith Busch1-1/+1
A previous commit aligning splits to physical block sizes inadvertently modified one return case such that that it now returns 0 length splits when the number of sectors doesn't exceed the physical offset. This later hits a BUG in bio_split(). Restore the previous working behavior. Fixes: 9cc5169cd478b ("block: Improve physical block alignment of split bios") Reported-by: Eric Deal <eric.deal@wdc.com> Signed-off-by: Keith Busch <kbusch@kernel.org> Cc: Bart Van Assche <bvanassche@acm.org> Cc: stable@vger.kernel.org Signed-off-by: Jens Axboe <axboe@kernel.dk>
2020-08-21blk-mq: insert request not through ->queue_rq into sw/scheduler queueMing Lei1-1/+2
c616cbee97ae ("blk-mq: punt failed direct issue to dispatch list") supposed to add request which has been through ->queue_rq() to the hw queue dispatch list, however it adds request running out of budget or driver tag to hw queue too. This way basically bypasses request merge, and causes too many request dispatched to LLD, and system% is unnecessary increased. Fixes this issue by adding request not through ->queue_rq into sw/scheduler queue, and this way is safe because no ->queue_rq is called on this request yet. High %system can be observed on Azure storvsc device, and even soft lock is observed. This patch reduces %system during heavy sequential IO, meantime decreases soft lockup risk. Fixes: c616cbee97ae ("blk-mq: punt failed direct issue to dispatch list") Signed-off-by: Ming Lei <ming.lei@redhat.com> Cc: Christoph Hellwig <hch@lst.de> Cc: Bart Van Assche <bvanassche@acm.org> Cc: Mike Snitzer <snitzer@redhat.com> Signed-off-by: Jens Axboe <axboe@kernel.dk>
2020-08-18bfq: fix blkio cgroup leakage v4Dmitry Monakhov3-12/+3
Changes from v1: - update commit description with proper ref-accounting justification commit db37a34c563b ("block, bfq: get a ref to a group when adding it to a service tree") introduce leak forbfq_group and blkcg_gq objects because of get/put imbalance. In fact whole idea of original commit is wrong because bfq_group entity can not dissapear under us because it is referenced by child bfq_queue's entities from here: -> bfq_init_entity() ->bfqg_and_blkg_get(bfqg); ->entity->parent = bfqg->my_entity -> bfq_put_queue(bfqq) FINAL_PUT ->bfqg_and_blkg_put(bfqq_group(bfqq)) ->kmem_cache_free(bfq_pool, bfqq); So parent entity can not disappear while child entity is in tree, and child entities already has proper protection. This patch revert commit db37a34c563b ("block, bfq: get a ref to a group when adding it to a service tree") bfq_group leak trace caused by bad commit: -> blkg_alloc -> bfq_pq_alloc -> bfqg_get (+1) ->bfq_activate_bfqq ->bfq_activate_requeue_entity -> __bfq_activate_entity ->bfq_get_entity ->bfqg_and_blkg_get (+1) <==== : Note1 ->bfq_del_bfqq_busy ->bfq_deactivate_entity+0x53/0xc0 [bfq] ->__bfq_deactivate_entity+0x1b8/0x210 [bfq] -> bfq_forget_entity(is_in_service = true) entity->on_st_or_in_serv = false <=== :Note2 if (is_in_service) return; ==> do not touch reference -> blkcg_css_offline -> blkcg_destroy_blkgs -> blkg_destroy -> bfq_pd_offline -> __bfq_deactivate_entity if (!entity->on_st_or_in_serv) /* true, because (Note2) return false; -> bfq_pd_free -> bfqg_put() (-1, byt bfqg->ref == 2) because of (Note2) So bfq_group and blkcg_gq will leak forever, see test-case below. ##TESTCASE_BEGIN: #!/bin/bash max_iters=${1:-100} #prep cgroup mounts mount -t tmpfs cgroup_root /sys/fs/cgroup mkdir /sys/fs/cgroup/blkio mount -t cgroup -o blkio none /sys/fs/cgroup/blkio # Prepare blkdev grep blkio /proc/cgroups truncate -s 1M img losetup /dev/loop0 img echo bfq > /sys/block/loop0/queue/scheduler grep blkio /proc/cgroups for ((i=0;i<max_iters;i++)) do mkdir -p /sys/fs/cgroup/blkio/a echo 0 > /sys/fs/cgroup/blkio/a/cgroup.procs dd if=/dev/loop0 bs=4k count=1 of=/dev/null iflag=direct 2> /dev/null echo 0 > /sys/fs/cgroup/blkio/cgroup.procs rmdir /sys/fs/cgroup/blkio/a grep blkio /proc/cgroups done ##TESTCASE_END: Fixes: db37a34c563b ("block, bfq: get a ref to a group when adding it to a service tree") Tested-by: Oleksandr Natalenko <oleksandr@natalenko.name> Signed-off-by: Dmitry Monakhov <dmtrmonakhov@yandex-team.ru> Signed-off-by: Jens Axboe <axboe@kernel.dk>
2020-08-17block: Fix page_is_mergeable() for compound pagesMatthew Wilcox (Oracle)1-5/+5
If we pass in an offset which is larger than PAGE_SIZE, then page_is_mergeable() thinks it's not mergeable with the previous bio_vec, leading to a large number of bio_vecs being used. Use a slightly more obvious test that the two pages are compatible with each other. Fixes: 52d52d1c98a9 ("block: only allow contiguous page structs in a bio_vec") Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org> Reviewed-by: Ming Lei <ming.lei@redhat.com> Signed-off-by: Jens Axboe <axboe@kernel.dk>
2020-08-17block: respect queue limit of max discard segmentMing Lei1-2/+9
When queue_max_discard_segments(q) is 1, blk_discard_mergable() will return false for discard request, then normal request merge is applied. However, only queue_max_segments() is checked, so max discard segment limit isn't respected. Check max discard segment limit in the request merge code for fixing the issue. Discard request failure of virtio_blk is fixed. Fixes: 69840466086d ("block: fix the DISCARD request merge") Signed-off-by: Ming Lei <ming.lei@redhat.com> Reviewed-by: Christoph Hellwig <hch@lst.de> Cc: Stefano Garzarella <sgarzare@redhat.com> Signed-off-by: Jens Axboe <axboe@kernel.dk>
2020-08-17blk-mq: order adding requests to hctx->dispatch and checking SCHED_RESTARTMing Lei2-0/+18
SCHED_RESTART code path is relied to re-run queue for dispatch requests in hctx->dispatch. Meantime the SCHED_RSTART flag is checked when adding requests to hctx->dispatch. memory barriers have to be used for ordering the following two pair of OPs: 1) adding requests to hctx->dispatch and checking SCHED_RESTART in blk_mq_dispatch_rq_list() 2) clearing SCHED_RESTART and checking if there is request in hctx->dispatch in blk_mq_sched_restart(). Without the added memory barrier, either: 1) blk_mq_sched_restart() may miss requests added to hctx->dispatch meantime blk_mq_dispatch_rq_list() observes SCHED_RESTART, and not run queue in dispatch side or 2) blk_mq_dispatch_rq_list still sees SCHED_RESTART, and not run queue in dispatch side, meantime checking if there is request in hctx->dispatch from blk_mq_sched_restart() is missed. IO hang in ltp/fs_fill test is reported by kernel test robot: https://lkml.org/lkml/2020/7/26/77 Turns out it is caused by the above out-of-order OPs. And the IO hang can't be observed any more after applying this patch. Fixes: bd166ef183c2 ("blk-mq-sched: add framework for MQ capable IO schedulers") Reported-by: kernel test robot <rong.a.chen@intel.com> Signed-off-by: Ming Lei <ming.lei@redhat.com> Reviewed-by: Christoph Hellwig <hch@lst.de> Cc: Bart Van Assche <bvanassche@acm.org> Cc: Christoph Hellwig <hch@lst.de> Cc: David Jeffery <djeffery@redhat.com> Cc: <stable@vger.kernel.org> Signed-off-by: Jens Axboe <axboe@kernel.dk>
2020-08-16bsg-lib: convert comma to semicolonXu Wang1-1/+1
Replace a comma between expression statements by a semicolon. Signed-off-by: Xu Wang <vulab@iscas.ac.cn> Signed-off-by: Jens Axboe <axboe@kernel.dk>
2020-08-16block: blk-mq.c: fix @at_head kernel-doc warningRandy Dunlap1-0/+1
Fix a kernel-doc warning in block/blk-mq.c: ../block/blk-mq.c:1844: warning: Function parameter or member 'at_head' not described in 'blk_mq_request_bypass_insert' Fixes: 01e99aeca397 ("blk-mq: insert passthrough request into hctx->dispatch directly") Signed-off-by: Randy Dunlap <rdunlap@infradead.org> Cc: André Almeida <andrealmeid@collabora.com> Cc: Jens Axboe <axboe@kernel.dk> Cc: Ming Lei <ming.lei@redhat.com> Cc: linux-block@vger.kernel.org Signed-off-by: Jens Axboe <axboe@kernel.dk>
2020-08-15Merge tag 'block-5.9-2020-08-14' of git://git.kernel.dk/linux-blockLinus Torvalds2-2/+18
Pull block fixes from Jens Axboe: "A few fixes on the block side of things: - Discard granularity fix (Coly) - rnbd cleanups (Guoqing) - md error handling fix (Dan) - md sysfs fix (Junxiao) - Fix flush request accounting, which caused an IO slowdown for some configurations (Ming) - Properly propagate loop flag for partition scanning (Lennart)" * tag 'block-5.9-2020-08-14' of git://git.kernel.dk/linux-block: block: fix double account of flush request's driver tag loop: unset GENHD_FL_NO_PART_SCAN on LOOP_CONFIGURE rnbd: no need to set bi_end_io in rnbd_bio_map_kern rnbd: remove rnbd_dev_submit_io md-cluster: Fix potential error pointer dereference in resize_bitmaps() block: check queue's limits.discard_granularity in __blkdev_issue_discard() md: get sysfs entry after redundancy attr group create
generated by cgit v1.2.3 (git 2.25.1) at 2025-08-26 01:03:16 +0000