To avoid recursion on the kernel stack when stacked block devices are in use, generic_make_request() will, when called recursively, queue new requests for later handling. They will be handled when the make_request_fn for the current bio completes. If any bios are submitted by a make_request_fn, these will ultimately be handled seqeuntially. If the handling of one of those generates further requests, they will be added to the end of the queue. This strict first-in-first-out behaviour can lead to deadlocks in various ways, normally because a request might need to wait for a previous request to the same device to complete. This can happen when they share a mempool, and can happen due to interdependencies particular to the device. Both md and dm have examples where this happens. These deadlocks can be erradicated by more selective ordering of bios. Specifically by handling them in depth-first order. That is: when the handling of one bio generates one or more further bios, they are handled immediately after the parent, before any siblings of the parent. That way, when generic_make_request() calls make_request_fn for some particular device, we can be certain that all previously submited requests for that device have been completely handled and are not waiting for anything in the queue of requests maintained in generic_make_request(). An easy way to achieve this would be to use a last-in-first-out stack instead of a queue. However this will change the order of consecutive bios submitted by a make_request_fn, which could have unexpected consequences. Instead we take a slightly more complex approach. A fresh queue is created for each call to a make_request_fn. After it completes, any bios for a different device are placed on the front of the main queue, followed by any bios for the same device, followed by all bios that were already on the queue before the make_request_fn was called. This provides the depth-first approach without reordering bios on the same level. This, by itself, it not enough to remove all deadlocks. It just makes it possible for drivers to take the extra step required themselves. To avoid deadlocks, drivers must never risk waiting for a request after submitting one to generic_make_request. This includes never allocing from a mempool twice in the one call to a make_request_fn. A common pattern in drivers is to call bio_split() in a loop, handling the first part and then looping around to possibly split the next part. Instead, a driver that finds it needs to split a bio should queue (with generic_make_request) the second part, handle the first part, and then return. The new code in generic_make_request will ensure the requests to underlying bios are processed first, then the second bio that was split off. If it splits again, the same process happens. In each case one bio will be completely handled before the next one is attempted. With this is place, it should be possible to disable the punt_bios_to_recover() recovery thread for many block devices, and eventually it may be possible to remove it completely. Ref: http://www.spinics.net/lists/raid/msg54680.html Tested-by: Jinpu Wang <jinpu.wang@profitbricks.com> Inspired-by: Lars Ellenberg <lars.ellenberg@linbit.com> Signed-off-by: NeilBrown <neilb@suse.com> Signed-off-by: Jens Axboe <axboe@fb.com>
This reverts commit 0dba1314d4f81115dce711292ec7981d17231064. It causes leaking of device numbers for SCSI when SCSI registers multiple gendisks for one request_queue in succession. It can be easily reproduced using Omar's script [1] on kernel with CONFIG_DEBUG_TEST_DRIVER_REMOVE. Furthermore the protection provided by this commit is not needed anymore as the problem it was fixing got also fixed by commit 165a5e22fafb "block: Move bdi_unregister() to del_gendisk()". [1]: http://marc.info/?l=linux-block&m=148554717109098&w=2 Signed-off-by: Jan Kara <jack@suse.cz> Acked-by: Dan Williams <dan.j.williams@intel.com> Tested-by: Omar Sandoval <osandov@fb.com> Signed-off-by: Jens Axboe <axboe@fb.com>
Commit 165a5e22fafb "block: Move bdi_unregister() to del_gendisk()" added disk->queue dereference to del_gendisk(). Although del_gendisk() is not supposed to be called without disk->queue valid and blk_unregister_queue() warns in that case, this change will make it oops instead. Return to the old more robust behavior of just warning when del_gendisk() gets called for gendisk with disk->queue being NULL. Reported-by: Dan Carpenter <dan.carpenter@oracle.com> Signed-off-by: Jan Kara <jack@suse.cz> Tested-by: Omar Sandoval <osandov@fb.com> Signed-off-by: Jens Axboe <axboe@fb.com>
Fixes check that the opal user is within the range, and cleans up unused method variables. Signed-off-by: Jon Derrick <jonathan.derrick@intel.com> Reviewed-by: Scott Bauer <scott.bauer@intel.com> Signed-off-by: Jens Axboe <axboe@fb.com>
It is obviously that hctx->cpumask is per hctx, and both share same lifetime, so this patch moves freeing of hctx->cpumask into release handler of hctx's kobject. Signed-off-by: Ming Lei <tom.leiming@gmail.com> Tested-by: Peter Zijlstra (Intel) <peterz@infradead.org> Signed-off-by: Jens Axboe <axboe@fb.com>
This patch removes kobject_put() over hctx in __blk_mq_unregister_dev(), and trys to keep lifetime consistent between hctx and hctx's kobject. Now blk_mq_sysfs_register() and blk_mq_sysfs_unregister() become totally symmetrical, and kobject's refcounter drops to zero just when the hctx is freed. Signed-off-by: Ming Lei <tom.leiming@gmail.com> Tested-by: Peter Zijlstra (Intel) <peterz@infradead.org> Signed-off-by: Jens Axboe <axboe@fb.com>
Currently from kobject view, both q->mq_kobj and ctx->kobj can be released during one cycle of blk_mq_register_dev() and blk_mq_unregister_dev(). Actually, sw queue's lifetime is same with its request queue's, which is covered by request_queue->kobj. So we don't need to call kobject_put() for the two kinds of kobject in __blk_mq_unregister_dev(), instead we do that in release handler of request queue. Signed-off-by: Ming Lei <tom.leiming@gmail.com> Tested-by: Peter Zijlstra (Intel) <peterz@infradead.org> Signed-off-by: Jens Axboe <axboe@fb.com>
Both q->mq_kobj and sw queues' kobjects should have been initialized once, instead of doing that each add_disk context. Also this patch removes clearing of ctx in blk_mq_init_cpu_queues() because percpu allocator fills zero to allocated variable. This patch fixes one issue[1] reported from Omar. [1] kernel wearning when doing unbind/bind on one scsi-mq device [ 19.347924] kobject (ffff8800791ea0b8): tried to init an initialized object, something is seriously wrong. [ 19.349781] CPU: 1 PID: 84 Comm: kworker/u8:1 Not tainted 4.10.0-rc7-00210-g53f39eeaa263 #34 [ 19.350686] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.10.1-20161122_114906-anatol 04/01/2014 [ 19.350920] Workqueue: events_unbound async_run_entry_fn [ 19.350920] Call Trace: [ 19.350920] dump_stack+0x63/0x83 [ 19.350920] kobject_init+0x77/0x90 [ 19.350920] blk_mq_register_dev+0x40/0x130 [ 19.350920] blk_register_queue+0xb6/0x190 [ 19.350920] device_add_disk+0x1ec/0x4b0 [ 19.350920] sd_probe_async+0x10d/0x1c0 [sd_mod] [ 19.350920] async_run_entry_fn+0x48/0x150 [ 19.350920] process_one_work+0x1d0/0x480 [ 19.350920] worker_thread+0x48/0x4e0 [ 19.350920] kthread+0x101/0x140 [ 19.350920] ? process_one_work+0x480/0x480 [ 19.350920] ? kthread_create_on_node+0x60/0x60 [ 19.350920] ret_from_fork+0x2c/0x40 Cc: Omar Sandoval <osandov@osandov.com> Signed-off-by: Ming Lei <tom.leiming@gmail.com> Tested-by: Peter Zijlstra (Intel) <peterz@infradead.org> Signed-off-by: Jens Axboe <axboe@fb.com>
Pull block layer fixes from Jens Axboe:
"A collection of fixes for this merge window, either fixes for existing
issues, or parts that were waiting for acks to come in. This pull
request contains:
- Allocation of nvme queues on the right node from Shaohua.
This was ready long before the merge window, but waiting on an ack
from Bjorn on the PCI bit. Now that we have that, the three patches
can go in.
- Two fixes for blk-mq-sched with nvmeof, which uses hctx specific
request allocations. This caused an oops. One part from Sagi, one
part from Omar.
- A loop partition scan deadlock fix from Omar, fixing a regression
in this merge window.
- A three-patch series from Keith, closing up a hole on clearing out
requests on shutdown/resume.
- A stable fix for nbd from Josef, fixing a leak of sockets.
- Two fixes for a regression in this window from Jan, fixing a
problem with one of his earlier patches dealing with queue vs bdi
life times.
- A fix for a regression with virtio-blk, causing an IO stall if
scheduling is used. From me.
- A fix for an io context lock ordering problem. From me"
* 'for-linus' of git://git.kernel.dk/linux-block:
block: Move bdi_unregister() to del_gendisk()
blk-mq: ensure that bd->last is always set correctly
block: don't call ioc_exit_icq() with the queue lock held for blk-mq
block: Initialize bd_bdi on inode initialization
loop: fix LO_FLAGS_PARTSCAN hang
nvme: Complete all stuck requests
blk-mq: Provide freeze queue timeout
blk-mq: Export blk_mq_freeze_queue_wait
nbd: stop leaking sockets
blk-mq: move update of tags->rqs to __blk_mq_alloc_request()
blk-mq: kill blk_mq_set_alloc_data()
blk-mq: make blk_mq_alloc_request_hctx() allocate a scheduler request
blk-mq-sched: Allocate sched reserved tags as specified in the original queue tagset
nvme: allocate nvme_queue in correct node
PCI: add an API to get node from vector
blk-mq: allocate blk_mq_tags and requests in correct node
Pull sched.h split-up from Ingo Molnar: "The point of these changes is to significantly reduce the <linux/sched.h> header footprint, to speed up the kernel build and to have a cleaner header structure. After these changes the new <linux/sched.h>'s typical preprocessed size goes down from a previous ~0.68 MB (~22K lines) to ~0.45 MB (~15K lines), which is around 40% faster to build on typical configs. Not much changed from the last version (-v2) posted three weeks ago: I eliminated quirks, backmerged fixes plus I rebased it to an upstream SHA1 from yesterday that includes most changes queued up in -next plus all sched.h changes that were pending from Andrew. I've re-tested the series both on x86 and on cross-arch defconfigs, and did a bisectability test at a number of random points. I tried to test as many build configurations as possible, but some build breakage is probably still left - but it should be mostly limited to architectures that have no cross-compiler binaries available on kernel.org, and non-default configurations" * 'WIP.sched-core-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: (146 commits) sched/headers: Clean up <linux/sched.h> sched/headers: Remove #ifdefs from <linux/sched.h> sched/headers: Remove the <linux/topology.h> include from <linux/sched.h> sched/headers, hrtimer: Remove the <linux/wait.h> include from <linux/hrtimer.h> sched/headers, x86/apic: Remove the <linux/pm.h> header inclusion from <asm/apic.h> sched/headers, timers: Remove the <linux/sysctl.h> include from <linux/timer.h> sched/headers: Remove <linux/magic.h> from <linux/sched/task_stack.h> sched/headers: Remove <linux/sched.h> from <linux/sched/init.h> sched/core: Remove unused prefetch_stack() sched/headers: Remove <linux/rculist.h> from <linux/sched.h> sched/headers: Remove the 'init_pid_ns' prototype from <linux/sched.h> sched/headers: Remove <linux/signal.h> from <linux/sched.h> sched/headers: Remove <linux/rwsem.h> from <linux/sched.h> sched/headers: Remove the runqueue_is_locked() prototype sched/headers: Remove <linux/sched.h> from <linux/sched/hotplug.h> sched/headers: Remove <linux/sched.h> from <linux/sched/debug.h> sched/headers: Remove <linux/sched.h> from <linux/sched/nohz.h> sched/headers: Remove <linux/sched.h> from <linux/sched/stat.h> sched/headers: Remove the <linux/gfp.h> include from <linux/sched.h> sched/headers: Remove <linux/rtmutex.h> from <linux/sched.h> ...