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path: root/block/blk-rq-qos.c
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2023-09-18block: correct stale comment in rq_qos_waitKemeng Shi
The rq_qos_wait calls common wake-up function rq_qos_wake_function to get token. Just replace stale wbt_wake_function with rq_qos_wake_function in comment. Signed-off-by: Kemeng Shi <shikemeng@huaweicloud.com> Acked-by: Tejun Heo <tj@kernel.org> Link: https://lore.kernel.org/r/20230914091508.36232-1-shikemeng@huaweicloud.com Signed-off-by: Jens Axboe <axboe@kernel.dk>
2023-05-23block/rq_qos: protect rq_qos apis with a new lockYu Kuai
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 destruction is supported in the furture, this patch also protect rq_qos_add() from wbt_init() directly, this is enough because blk-sysfs already synchronize writers with disk removal. 3) For iocost and iolatency, in order to synchronize disk removal and cgroup configuration, the lock is held after blkdev_get_no_open() from blkg_conf_open_bdev(), and is released in blkg_conf_exit(). In order to fix the above memory leak, disk_live() is checked after holding the new lock. Fixes: 50e34d78815e ("block: disable the elevator int del_gendisk") Signed-off-by: Yu Kuai <yukuai3@huawei.com> Acked-by: Tejun Heo <tj@kernel.org> Link: https://lore.kernel.org/r/20230414084008.2085155-1-yukuai1@huaweicloud.com Signed-off-by: Jens Axboe <axboe@kernel.dk>
2023-02-03blk-rq-qos: store a gendisk instead of request_queue in struct rq_qosChristoph Hellwig
This is what about half of the users already want, and it's only going to grow more. Signed-off-by: Christoph Hellwig <hch@lst.de> Reviewed-by: Andreas Herrmann <aherrmann@suse.de> Acked-by: Tejun Heo <tj@kernel.org> Link: https://lore.kernel.org/r/20230203150400.3199230-16-hch@lst.de Signed-off-by: Jens Axboe <axboe@kernel.dk>
2023-02-03blk-rq-qos: constify rq_qos_opsChristoph Hellwig
These op vectors are constant, so mark them const. Signed-off-by: Christoph Hellwig <hch@lst.de> Reviewed-by: Andreas Herrmann <aherrmann@suse.de> Acked-by: Tejun Heo <tj@kernel.org> Link: https://lore.kernel.org/r/20230203150400.3199230-15-hch@lst.de Signed-off-by: Jens Axboe <axboe@kernel.dk>
2023-02-03blk-rq-qos: make rq_qos_add and rq_qos_del more usefulChristoph Hellwig
Switch to passing a gendisk, and make rq_qos_add initialize all required fields and drop the not required q argument from rq_qos_del. Signed-off-by: Christoph Hellwig <hch@lst.de> Reviewed-by: Andreas Herrmann <aherrmann@suse.de> Acked-by: Tejun Heo <tj@kernel.org> Link: https://lore.kernel.org/r/20230203150400.3199230-14-hch@lst.de Signed-off-by: Jens Axboe <axboe@kernel.dk>
2023-02-03blk-rq-qos: move rq_qos_add and rq_qos_del out of lineChristoph Hellwig
These two functions are rather larger and not in a fast path, so move them out of line. Signed-off-by: Christoph Hellwig <hch@lst.de> Acked-by: Tejun Heo <tj@kernel.org> Link: https://lore.kernel.org/r/20230203150400.3199230-13-hch@lst.de Signed-off-by: Jens Axboe <axboe@kernel.dk>
2022-07-12block/rq_qos: Use atomic_try_cmpxchg in atomic_inc_belowUros Bizjak
Use atomic_try_cmpxchg instead of atomic_cmpxchg (*ptr, old, new) == old in atomic_inc_below. x86 CMPXCHG instruction returns success in ZF flag, so this change saves a compare after cmpxchg (and related move instruction in front of cmpxchg). Also, atomic_try_cmpxchg implicitly assigns old *ptr value to "old" when cmpxchg fails, enabling further code simplifications. No functional change intended. Signed-off-by: Uros Bizjak <ubizjak@gmail.com> Cc: Jens Axboe <axboe@kernel.dk> Link: https://lore.kernel.org/r/20220712150547.5786-1-ubizjak@gmail.com Signed-off-by: Jens Axboe <axboe@kernel.dk>
2022-06-17block: remove per-disk debugfs files in blk_unregister_queueChristoph Hellwig
The block debugfs files are created in blk_register_queue, which is called by add_disk and use a naming scheme based on the disk_name. After del_gendisk returns that name can be reused and thus we must not leave these debugfs files around, otherwise the kernel is unhappy and spews messages like: Directory XXXXX with parent 'block' already present! and the newly created devices will not have working debugfs files. Move the unregistration to blk_unregister_queue instead (which matches the sysfs unregistration) to make sure the debugfs life time rules match those of the disk name. As part of the move also make sure the whole debugfs unregistration is inside a single debugfs_mutex critical section. Note that this breaks blktests block/002, which checks that the debugfs directory has not been removed while blktests is running, but that particular check should simply be removed from the test case. Signed-off-by: Christoph Hellwig <hch@lst.de> Link: https://lore.kernel.org/r/20220614074827.458955-4-hch@lst.de Signed-off-by: Jens Axboe <axboe@kernel.dk>
2022-06-17block: serialize all debugfs operations using q->debugfs_mutexChristoph Hellwig
Various places like I/O schedulers or the QOS infrastructure try to register debugfs files on demans, which can race with creating and removing the main queue debugfs directory. Use the existing debugfs_mutex to serialize all debugfs operations that rely on q->debugfs_dir or the directories hanging off it. To make the teardown code a little simpler declare all debugfs dentry pointers and not just the main one uncoditionally in blkdev.h. Move debugfs_mutex next to the dentries that it protects and document what it is used for. Signed-off-by: Christoph Hellwig <hch@lst.de> Link: https://lore.kernel.org/r/20220614074827.458955-3-hch@lst.de Signed-off-by: Jens Axboe <axboe@kernel.dk>
2021-06-08rq-qos: fix missed wake-ups in rq_qos_throttle try twoJan Kara
Commit 545fbd0775ba ("rq-qos: fix missed wake-ups in rq_qos_throttle") tried to fix a problem that a process could be sleeping in rq_qos_wait() without anyone to wake it up. However the fix is not complete and the following can still happen: CPU1 (waiter1) CPU2 (waiter2) CPU3 (waker) rq_qos_wait() rq_qos_wait() acquire_inflight_cb() -> fails acquire_inflight_cb() -> fails completes IOs, inflight decreased prepare_to_wait_exclusive() prepare_to_wait_exclusive() has_sleeper = !wq_has_single_sleeper() -> true as there are two sleepers has_sleeper = !wq_has_single_sleeper() -> true io_schedule() io_schedule() Deadlock as now there's nobody to wakeup the two waiters. The logic automatically blocking when there are already sleepers is really subtle and the only way to make it work reliably is that we check whether there are some waiters in the queue when adding ourselves there. That way, we are guaranteed that at least the first process to enter the wait queue will recheck the waiting condition before going to sleep and thus guarantee forward progress. Fixes: 545fbd0775ba ("rq-qos: fix missed wake-ups in rq_qos_throttle") CC: stable@vger.kernel.org Signed-off-by: Jan Kara <jack@suse.cz> Link: https://lore.kernel.org/r/20210607112613.25344-1-jack@suse.cz Signed-off-by: Jens Axboe <axboe@kernel.dk>
2019-10-06blk-wbt: fix performance regression in wbt scale_up/scale_downHarshad Shirwadkar
scale_up wakes up waiters after scaling up. But after scaling max, it should not wake up more waiters as waiters will not have anything to do. This patch fixes this by making scale_up (and also scale_down) return when threshold is reached. This bug causes increased fdatasync latency when fdatasync and dd conv=sync are performed in parallel on 4.19 compared to 4.14. This bug was introduced during refactoring of blk-wbt code. Fixes: a79050434b45 ("blk-rq-qos: refactor out common elements of blk-wbt") Cc: stable@vger.kernel.org Cc: Josef Bacik <jbacik@fb.com> Signed-off-by: Harshad Shirwadkar <harshadshirwadkar@gmail.com> Signed-off-by: Jens Axboe <axboe@kernel.dk>
2019-08-28block/rq_qos: implement rq_qos_ops->queue_depth_changed()Tejun Heo
wbt already gets queue depth changed notification through wbt_set_queue_depth(). Generalize it into rq_qos_ops->queue_depth_changed() so that other rq_qos policies can easily hook into the events too. Signed-off-by: Tejun Heo <tj@kernel.org> Signed-off-by: Jens Axboe <axboe@kernel.dk>
2019-08-28block/rq_qos: add rq_qos_merge()Tejun Heo
Add a merge hook for rq_qos. This will be used by io.weight. Signed-off-by: Tejun Heo <tj@kernel.org> Signed-off-by: Jens Axboe <axboe@kernel.dk>
2019-07-18rq-qos: use a mb for got_tokenJosef Bacik
Oleg noticed that our checking of data.got_token is unsafe in the cleanup case, and should really use a memory barrier. Use a wmb on the write side, and a rmb() on the read side. We don't need one in the main loop since we're saved by set_current_state(). Reviewed-by: Oleg Nesterov <oleg@redhat.com> Signed-off-by: Josef Bacik <josef@toxicpanda.com> Signed-off-by: Jens Axboe <axboe@kernel.dk>
2019-07-18rq-qos: set ourself TASK_UNINTERRUPTIBLE after we scheduleJosef Bacik
In case we get a spurious wakeup we need to make sure to re-set ourselves to TASK_UNINTERRUPTIBLE so we don't busy wait. Reviewed-by: Oleg Nesterov <oleg@redhat.com> Signed-off-by: Josef Bacik <josef@toxicpanda.com> Signed-off-by: Jens Axboe <axboe@kernel.dk>
2019-07-18rq-qos: don't reset has_sleepers on spurious wakeupsJosef Bacik
If we raced with somebody else getting an inflight counter we could fail to get an inflight counter with no sleepers on the list, and thus need to go to sleep. In this case has_sleepers should be true because we are now relying on the waker to get our inflight counter for us. And in the case of spurious wakeups we'd still want this to be the case. So set has_sleepers to true if we went to sleep to make sure we're woken up the proper way. Reviewed-by: Oleg Nesterov <oleg@redhat.com> Signed-off-by: Josef Bacik <josef@toxicpanda.com> Signed-off-by: Jens Axboe <axboe@kernel.dk>
2019-07-18rq-qos: fix missed wake-ups in rq_qos_throttleJosef Bacik
We saw a hang in production with WBT where there was only one waiter in the throttle path and no outstanding IO. This is because of the has_sleepers optimization that is used to make sure we don't steal an inflight counter for new submitters when there are people already on the list. We can race with our check to see if the waitqueue has any waiters (this is done locklessly) and the time we actually add ourselves to the waitqueue. If this happens we'll go to sleep and never be woken up because nobody is doing IO to wake us up. Fix this by checking if the waitqueue has a single sleeper on the list after we add ourselves, that way we have an uptodate view of the list. Reviewed-by: Oleg Nesterov <oleg@redhat.com> Signed-off-by: Josef Bacik <josef@toxicpanda.com> Signed-off-by: Jens Axboe <axboe@kernel.dk>
2019-05-31block: Fix rq_qos_wait() kernel-doc headerBart Van Assche
Add documentation for the @rqw argument and change " - " into ": ". Fixes: 84f603246db9 ("block: add rq_qos_wait to rq_qos") # v5.0-rc1~52^2~140. Reviewed-by: Chaitanya Kulkarni <chiatanya.kulkarni@wdc.com> Signed-off-by: Bart Van Assche <bvanassche@acm.org> Signed-off-by: Jens Axboe <axboe@kernel.dk>
2019-04-30block: add SPDX tags to block layer files missing licensing informationChristoph Hellwig
Various block layer files do not have any licensing information at all. Add SPDX tags for the default kernel GPLv2 license to those. Reviewed-by: Chaitanya Kulkarni <chaitanya.kulkarni@wdc.com> Signed-off-by: Christoph Hellwig <hch@lst.de> Signed-off-by: Jens Axboe <axboe@kernel.dk>
2018-12-16blk-mq-debugfs: support rq_qosMing Lei
blk-mq-debugfs has been proved as very helpful for debug some tough issues, such as IO hang. We have seen blk-wbt related IO hang several times, even inside Red Hat BZ, there is such report not sovled yet, so this patch adds support debugfs on rq_qos. Cc: Bart Van Assche <bart.vanassche@wdc.com> Cc: Omar Sandoval <osandov@fb.com> Cc: Christoph Hellwig <hch@lst.de> Cc: Josef Bacik <josef@toxicpanda.com> Signed-off-by: Ming Lei <ming.lei@redhat.com> Signed-off-by: Jens Axboe <axboe@kernel.dk>
2018-12-07block: add rq_qos_wait to rq_qosJosef Bacik
Originally when I split out the common code from blk-wbt into rq_qos I left the wbt_wait() where it was and simply copied and modified it slightly to work for io-latency. However they are both basically the same thing, and as time has gone on wbt_wait() has ended up much smarter and kinder than it was when I copied it into io-latency, which means io-latency has lost out on these improvements. Since they are the same thing essentially except for a few minor things, create rq_qos_wait() that replicates what wbt_wait() currently does with callbacks that can be passed in for the snowflakes to do their own thing as appropriate. Signed-off-by: Josef Bacik <josef@toxicpanda.com> Signed-off-by: Jens Axboe <axboe@kernel.dk>
2018-11-16blk-rq-qos: inline check for q->rq_qos functionsJens Axboe
Put the short code in the fast path, where we don't have any functions attached to the queue. This minimizes the impact on the hot path in the core code. Cc: Josef Bacik <josef@toxicpanda.com> Reviewed-by: Christoph Hellwig <hch@lst.de> Signed-off-by: Jens Axboe <axboe@kernel.dk>
2018-11-15block: remove the unused lock argument to rq_qos_throttleChristoph Hellwig
Unused now that the legacy request path is gone. Reviewed-by: Hannes Reinecke <hare@suse.com> Signed-off-by: Christoph Hellwig <hch@lst.de> Signed-off-by: Jens Axboe <axboe@kernel.dk>
2018-07-22blk-rq-qos: make depth comparisons unsignedJosef Bacik
With the change to use UINT_MAX I broke the depth check as any value of inflight (ie 0) would be less than (int)UINT_MAX. Fix this by changing everything to unsigned int to match the depth. Signed-off-by: Josef Bacik <josef@toxicpanda.com> Signed-off-by: Jens Axboe <axboe@kernel.dk>
2018-07-09rq-qos: introduce dio_bio callbackJosef Bacik
wbt cares only about request completion time, but controllers may need information that is on the bio itself, so add a done_bio callback for rq-qos so things like blk-iolatency can use it to have the bio when it completes. Signed-off-by: Josef Bacik <jbacik@fb.com> Signed-off-by: Jens Axboe <axboe@kernel.dk>
2018-07-09block: remove external dependency on wbt_flagsJosef Bacik
We don't really need to save this stuff in the core block code, we can just pass the bio back into the helpers later on to derive the same flags and update the rq->wbt_flags appropriately. Signed-off-by: Josef Bacik <jbacik@fb.com> Signed-off-by: Jens Axboe <axboe@kernel.dk>
2018-07-09blk-rq-qos: refactor out common elements of blk-wbtJosef Bacik
blkcg-qos is going to do essentially what wbt does, only on a cgroup basis. Break out the common code that will be shared between blkcg-qos and wbt into blk-rq-qos.* so they can both utilize the same infrastructure. Signed-off-by: Josef Bacik <jbacik@fb.com> Signed-off-by: Jens Axboe <axboe@kernel.dk>