linux/block/blk-ioc.c

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License cleanup: add SPDX GPL-2.0 license identifier to files with no license Many source files in the tree are missing licensing information, which makes it harder for compliance tools to determine the correct license. By default all files without license information are under the default license of the kernel, which is GPL version 2. Update the files which contain no license information with the 'GPL-2.0' SPDX license identifier. The SPDX identifier is a legally binding shorthand, which can be used instead of the full boiler plate text. This patch is based on work done by Thomas Gleixner and Kate Stewart and Philippe Ombredanne. How this work was done: Patches were generated and checked against linux-4.14-rc6 for a subset of the use cases: - file had no licensing information it it. - file was a */uapi/* one with no licensing information in it, - file was a */uapi/* one with existing licensing information, Further patches will be generated in subsequent months to fix up cases where non-standard license headers were used, and references to license had to be inferred by heuristics based on keywords. The analysis to determine which SPDX License Identifier to be applied to a file was done in a spreadsheet of side by side results from of the output of two independent scanners (ScanCode & Windriver) producing SPDX tag:value files created by Philippe Ombredanne. Philippe prepared the base worksheet, and did an initial spot review of a few 1000 files. The 4.13 kernel was the starting point of the analysis with 60,537 files assessed. Kate Stewart did a file by file comparison of the scanner results in the spreadsheet to determine which SPDX license identifier(s) to be applied to the file. She confirmed any determination that was not immediately clear with lawyers working with the Linux Foundation. Criteria used to select files for SPDX license identifier tagging was: - Files considered eligible had to be source code files. - Make and config files were included as candidates if they contained >5 lines of source - File already had some variant of a license header in it (even if <5 lines). All documentation files were explicitly excluded. The following heuristics were used to determine which SPDX license identifiers to apply. - when both scanners couldn't find any license traces, file was considered to have no license information in it, and the top level COPYING file license applied. For non */uapi/* files that summary was: SPDX license identifier # files ---------------------------------------------------|------- GPL-2.0 11139 and resulted in the first patch in this series. If that file was a */uapi/* path one, it was "GPL-2.0 WITH Linux-syscall-note" otherwise it was "GPL-2.0". Results of that was: SPDX license identifier # files ---------------------------------------------------|------- GPL-2.0 WITH Linux-syscall-note 930 and resulted in the second patch in this series. - if a file had some form of licensing information in it, and was one of the */uapi/* ones, it was denoted with the Linux-syscall-note if any GPL family license was found in the file or had no licensing in it (per prior point). Results summary: SPDX license identifier # files ---------------------------------------------------|------ GPL-2.0 WITH Linux-syscall-note 270 GPL-2.0+ WITH Linux-syscall-note 169 ((GPL-2.0 WITH Linux-syscall-note) OR BSD-2-Clause) 21 ((GPL-2.0 WITH Linux-syscall-note) OR BSD-3-Clause) 17 LGPL-2.1+ WITH Linux-syscall-note 15 GPL-1.0+ WITH Linux-syscall-note 14 ((GPL-2.0+ WITH Linux-syscall-note) OR BSD-3-Clause) 5 LGPL-2.0+ WITH Linux-syscall-note 4 LGPL-2.1 WITH Linux-syscall-note 3 ((GPL-2.0 WITH Linux-syscall-note) OR MIT) 3 ((GPL-2.0 WITH Linux-syscall-note) AND MIT) 1 and that resulted in the third patch in this series. - when the two scanners agreed on the detected license(s), that became the concluded license(s). - when there was disagreement between the two scanners (one detected a license but the other didn't, or they both detected different licenses) a manual inspection of the file occurred. - In most cases a manual inspection of the information in the file resulted in a clear resolution of the license that should apply (and which scanner probably needed to revisit its heuristics). - When it was not immediately clear, the license identifier was confirmed with lawyers working with the Linux Foundation. - If there was any question as to the appropriate license identifier, the file was flagged for further research and to be revisited later in time. In total, over 70 hours of logged manual review was done on the spreadsheet to determine the SPDX license identifiers to apply to the source files by Kate, Philippe, Thomas and, in some cases, confirmation by lawyers working with the Linux Foundation. Kate also obtained a third independent scan of the 4.13 code base from FOSSology, and compared selected files where the other two scanners disagreed against that SPDX file, to see if there was new insights. The Windriver scanner is based on an older version of FOSSology in part, so they are related. Thomas did random spot checks in about 500 files from the spreadsheets for the uapi headers and agreed with SPDX license identifier in the files he inspected. For the non-uapi files Thomas did random spot checks in about 15000 files. In initial set of patches against 4.14-rc6, 3 files were found to have copy/paste license identifier errors, and have been fixed to reflect the correct identifier. Additionally Philippe spent 10 hours this week doing a detailed manual inspection and review of the 12,461 patched files from the initial patch version early this week with: - a full scancode scan run, collecting the matched texts, detected license ids and scores - reviewing anything where there was a license detected (about 500+ files) to ensure that the applied SPDX license was correct - reviewing anything where there was no detection but the patch license was not GPL-2.0 WITH Linux-syscall-note to ensure that the applied SPDX license was correct This produced a worksheet with 20 files needing minor correction. This worksheet was then exported into 3 different .csv files for the different types of files to be modified. These .csv files were then reviewed by Greg. Thomas wrote a script to parse the csv files and add the proper SPDX tag to the file, in the format that the file expected. This script was further refined by Greg based on the output to detect more types of files automatically and to distinguish between header and source .c files (which need different comment types.) Finally Greg ran the script using the .csv files to generate the patches. Reviewed-by: Kate Stewart <kstewart@linuxfoundation.org> Reviewed-by: Philippe Ombredanne <pombredanne@nexb.com> Reviewed-by: Thomas Gleixner <tglx@linutronix.de> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
2017-11-01 14:07:57 +00:00
// SPDX-License-Identifier: GPL-2.0
/*
* Functions related to io context handling
*/
#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/init.h>
#include <linux/bio.h>
#include <linux/blkdev.h>
include cleanup: Update gfp.h and slab.h includes to prepare for breaking implicit slab.h inclusion from percpu.h percpu.h is included by sched.h and module.h and thus ends up being included when building most .c files. percpu.h includes slab.h which in turn includes gfp.h making everything defined by the two files universally available and complicating inclusion dependencies. percpu.h -> slab.h dependency is about to be removed. Prepare for this change by updating users of gfp and slab facilities include those headers directly instead of assuming availability. As this conversion needs to touch large number of source files, the following script is used as the basis of conversion. http://userweb.kernel.org/~tj/misc/slabh-sweep.py The script does the followings. * Scan files for gfp and slab usages and update includes such that only the necessary includes are there. ie. if only gfp is used, gfp.h, if slab is used, slab.h. * When the script inserts a new include, it looks at the include blocks and try to put the new include such that its order conforms to its surrounding. It's put in the include block which contains core kernel includes, in the same order that the rest are ordered - alphabetical, Christmas tree, rev-Xmas-tree or at the end if there doesn't seem to be any matching order. * If the script can't find a place to put a new include (mostly because the file doesn't have fitting include block), it prints out an error message indicating which .h file needs to be added to the file. The conversion was done in the following steps. 1. The initial automatic conversion of all .c files updated slightly over 4000 files, deleting around 700 includes and adding ~480 gfp.h and ~3000 slab.h inclusions. The script emitted errors for ~400 files. 2. Each error was manually checked. Some didn't need the inclusion, some needed manual addition while adding it to implementation .h or embedding .c file was more appropriate for others. This step added inclusions to around 150 files. 3. The script was run again and the output was compared to the edits from #2 to make sure no file was left behind. 4. Several build tests were done and a couple of problems were fixed. e.g. lib/decompress_*.c used malloc/free() wrappers around slab APIs requiring slab.h to be added manually. 5. The script was run on all .h files but without automatically editing them as sprinkling gfp.h and slab.h inclusions around .h files could easily lead to inclusion dependency hell. Most gfp.h inclusion directives were ignored as stuff from gfp.h was usually wildly available and often used in preprocessor macros. Each slab.h inclusion directive was examined and added manually as necessary. 6. percpu.h was updated not to include slab.h. 7. Build test were done on the following configurations and failures were fixed. CONFIG_GCOV_KERNEL was turned off for all tests (as my distributed build env didn't work with gcov compiles) and a few more options had to be turned off depending on archs to make things build (like ipr on powerpc/64 which failed due to missing writeq). * x86 and x86_64 UP and SMP allmodconfig and a custom test config. * powerpc and powerpc64 SMP allmodconfig * sparc and sparc64 SMP allmodconfig * ia64 SMP allmodconfig * s390 SMP allmodconfig * alpha SMP allmodconfig * um on x86_64 SMP allmodconfig 8. percpu.h modifications were reverted so that it could be applied as a separate patch and serve as bisection point. Given the fact that I had only a couple of failures from tests on step 6, I'm fairly confident about the coverage of this conversion patch. If there is a breakage, it's likely to be something in one of the arch headers which should be easily discoverable easily on most builds of the specific arch. Signed-off-by: Tejun Heo <tj@kernel.org> Guess-its-ok-by: Christoph Lameter <cl@linux-foundation.org> Cc: Ingo Molnar <mingo@redhat.com> Cc: Lee Schermerhorn <Lee.Schermerhorn@hp.com>
2010-03-24 08:04:11 +00:00
#include <linux/slab.h>
#include <linux/security.h>
#include <linux/sched/task.h>
#include "blk.h"
#include "blk-mq-sched.h"
/*
* For io context allocations
*/
static struct kmem_cache *iocontext_cachep;
#ifdef CONFIG_BLK_ICQ
block: make ioc get/put interface more conventional and fix race on alloction Ignoring copy_io() during fork, io_context can be allocated from two places - current_io_context() and set_task_ioprio(). The former is always called from local task while the latter can be called from different task. The synchornization between them are peculiar and dubious. * current_io_context() doesn't grab task_lock() and assumes that if it saw %NULL ->io_context, it would stay that way until allocation and assignment is complete. It has smp_wmb() between alloc/init and assignment. * set_task_ioprio() grabs task_lock() for assignment and does smp_read_barrier_depends() between "ioc = task->io_context" and "if (ioc)". Unfortunately, this doesn't achieve anything - the latter is not a dependent load of the former. ie, if ioc itself were being dereferenced "ioc->xxx", it would mean something (not sure what tho) but as the code currently stands, the dependent read barrier is noop. As only one of the the two test-assignment sequences is task_lock() protected, the task_lock() can't do much about race between the two. Nothing prevents current_io_context() and set_task_ioprio() allocating its own ioc for the same task and overwriting the other's. Also, set_task_ioprio() can race with exiting task and create a new ioc after exit_io_context() is finished. ioc get/put doesn't have any reason to be complex. The only hot path is accessing the existing ioc of %current, which is simple to achieve given that ->io_context is never destroyed as long as the task is alive. All other paths can happily go through task_lock() like all other task sub structures without impacting anything. This patch updates ioc get/put so that it becomes more conventional. * alloc_io_context() is replaced with get_task_io_context(). This is the only interface which can acquire access to ioc of another task. On return, the caller has an explicit reference to the object which should be put using put_io_context() afterwards. * The functionality of current_io_context() remains the same but when creating a new ioc, it shares the code path with get_task_io_context() and always goes through task_lock(). * get_io_context() now means incrementing ref on an ioc which the caller already has access to (be that an explicit refcnt or implicit %current one). * PF_EXITING inhibits creation of new io_context and once exit_io_context() is finished, it's guaranteed that both ioc acquisition functions return %NULL. * All users are updated. Most are trivial but smp_read_barrier_depends() removal from cfq_get_io_context() needs a bit of explanation. I suppose the original intention was to ensure ioc->ioprio is visible when set_task_ioprio() allocates new io_context and installs it; however, this wouldn't have worked because set_task_ioprio() doesn't have wmb between init and install. There are other problems with this which will be fixed in another patch. * While at it, use NUMA_NO_NODE instead of -1 for wildcard node specification. -v2: Vivek spotted contamination from debug patch. Removed. Signed-off-by: Tejun Heo <tj@kernel.org> Cc: Vivek Goyal <vgoyal@redhat.com> Signed-off-by: Jens Axboe <axboe@kernel.dk>
2011-12-13 23:33:38 +00:00
/**
* get_io_context - increment reference count to io_context
* @ioc: io_context to get
*
* Increment reference count to @ioc.
*/
static void get_io_context(struct io_context *ioc)
block: make ioc get/put interface more conventional and fix race on alloction Ignoring copy_io() during fork, io_context can be allocated from two places - current_io_context() and set_task_ioprio(). The former is always called from local task while the latter can be called from different task. The synchornization between them are peculiar and dubious. * current_io_context() doesn't grab task_lock() and assumes that if it saw %NULL ->io_context, it would stay that way until allocation and assignment is complete. It has smp_wmb() between alloc/init and assignment. * set_task_ioprio() grabs task_lock() for assignment and does smp_read_barrier_depends() between "ioc = task->io_context" and "if (ioc)". Unfortunately, this doesn't achieve anything - the latter is not a dependent load of the former. ie, if ioc itself were being dereferenced "ioc->xxx", it would mean something (not sure what tho) but as the code currently stands, the dependent read barrier is noop. As only one of the the two test-assignment sequences is task_lock() protected, the task_lock() can't do much about race between the two. Nothing prevents current_io_context() and set_task_ioprio() allocating its own ioc for the same task and overwriting the other's. Also, set_task_ioprio() can race with exiting task and create a new ioc after exit_io_context() is finished. ioc get/put doesn't have any reason to be complex. The only hot path is accessing the existing ioc of %current, which is simple to achieve given that ->io_context is never destroyed as long as the task is alive. All other paths can happily go through task_lock() like all other task sub structures without impacting anything. This patch updates ioc get/put so that it becomes more conventional. * alloc_io_context() is replaced with get_task_io_context(). This is the only interface which can acquire access to ioc of another task. On return, the caller has an explicit reference to the object which should be put using put_io_context() afterwards. * The functionality of current_io_context() remains the same but when creating a new ioc, it shares the code path with get_task_io_context() and always goes through task_lock(). * get_io_context() now means incrementing ref on an ioc which the caller already has access to (be that an explicit refcnt or implicit %current one). * PF_EXITING inhibits creation of new io_context and once exit_io_context() is finished, it's guaranteed that both ioc acquisition functions return %NULL. * All users are updated. Most are trivial but smp_read_barrier_depends() removal from cfq_get_io_context() needs a bit of explanation. I suppose the original intention was to ensure ioc->ioprio is visible when set_task_ioprio() allocates new io_context and installs it; however, this wouldn't have worked because set_task_ioprio() doesn't have wmb between init and install. There are other problems with this which will be fixed in another patch. * While at it, use NUMA_NO_NODE instead of -1 for wildcard node specification. -v2: Vivek spotted contamination from debug patch. Removed. Signed-off-by: Tejun Heo <tj@kernel.org> Cc: Vivek Goyal <vgoyal@redhat.com> Signed-off-by: Jens Axboe <axboe@kernel.dk>
2011-12-13 23:33:38 +00:00
{
BUG_ON(atomic_long_read(&ioc->refcount) <= 0);
atomic_long_inc(&ioc->refcount);
}
static void icq_free_icq_rcu(struct rcu_head *head)
{
struct io_cq *icq = container_of(head, struct io_cq, __rcu_head);
kmem_cache_free(icq->__rcu_icq_cache, icq);
}
/*
* Exit an icq. Called with ioc locked for blk-mq, and with both ioc
* and queue locked for legacy.
*/
static void ioc_exit_icq(struct io_cq *icq)
block: exit_io_context() should call elevator_exit_icq_fn() While updating locking, b2efa05265 "block, cfq: unlink cfq_io_context's immediately" moved elevator_exit_icq_fn() invocation from exit_io_context() to the final ioc put. While this doesn't cause catastrophic failure, it effectively removes task exit notification to elevator and cause noticeable IO performance degradation with CFQ. On task exit, CFQ used to immediately expire the slice if it was being used by the exiting task as no more IO would be issued by the task; however, after b2efa05265, the notification is lost and disk could sit idle needlessly, leading to noticeable IO performance degradation for certain workloads. This patch renames ioc_exit_icq() to ioc_destroy_icq(), separates elevator_exit_icq_fn() invocation into ioc_exit_icq() and invokes it from exit_io_context(). ICQ_EXITED flag is added to avoid invoking the callback more than once for the same icq. Walking icq_list from ioc side and invoking elevator callback requires reverse double locking. This may be better implemented using RCU; unfortunately, using RCU isn't trivial. e.g. RCU protection would need to cover request_queue and queue_lock switch on cleanup makes grabbing queue_lock from RCU unsafe. Reverse double locking should do, at least for now. Signed-off-by: Tejun Heo <tj@kernel.org> Reported-and-bisected-by: Shaohua Li <shli@kernel.org> LKML-Reference: <CANejiEVzs=pUhQSTvUppkDcc2TNZyfohBRLygW5zFmXyk5A-xQ@mail.gmail.com> Tested-by: Shaohua Li <shaohua.li@intel.com> Signed-off-by: Jens Axboe <axboe@kernel.dk>
2012-02-15 08:45:53 +00:00
{
struct elevator_type *et = icq->q->elevator->type;
if (icq->flags & ICQ_EXITED)
return;
if (et->ops.exit_icq)
et->ops.exit_icq(icq);
block: exit_io_context() should call elevator_exit_icq_fn() While updating locking, b2efa05265 "block, cfq: unlink cfq_io_context's immediately" moved elevator_exit_icq_fn() invocation from exit_io_context() to the final ioc put. While this doesn't cause catastrophic failure, it effectively removes task exit notification to elevator and cause noticeable IO performance degradation with CFQ. On task exit, CFQ used to immediately expire the slice if it was being used by the exiting task as no more IO would be issued by the task; however, after b2efa05265, the notification is lost and disk could sit idle needlessly, leading to noticeable IO performance degradation for certain workloads. This patch renames ioc_exit_icq() to ioc_destroy_icq(), separates elevator_exit_icq_fn() invocation into ioc_exit_icq() and invokes it from exit_io_context(). ICQ_EXITED flag is added to avoid invoking the callback more than once for the same icq. Walking icq_list from ioc side and invoking elevator callback requires reverse double locking. This may be better implemented using RCU; unfortunately, using RCU isn't trivial. e.g. RCU protection would need to cover request_queue and queue_lock switch on cleanup makes grabbing queue_lock from RCU unsafe. Reverse double locking should do, at least for now. Signed-off-by: Tejun Heo <tj@kernel.org> Reported-and-bisected-by: Shaohua Li <shli@kernel.org> LKML-Reference: <CANejiEVzs=pUhQSTvUppkDcc2TNZyfohBRLygW5zFmXyk5A-xQ@mail.gmail.com> Tested-by: Shaohua Li <shaohua.li@intel.com> Signed-off-by: Jens Axboe <axboe@kernel.dk>
2012-02-15 08:45:53 +00:00
icq->flags |= ICQ_EXITED;
}
static void ioc_exit_icqs(struct io_context *ioc)
{
struct io_cq *icq;
spin_lock_irq(&ioc->lock);
hlist_for_each_entry(icq, &ioc->icq_list, ioc_node)
ioc_exit_icq(icq);
spin_unlock_irq(&ioc->lock);
}
/*
* Release an icq. Called with ioc locked for blk-mq, and with both ioc
* and queue locked for legacy.
*/
block: exit_io_context() should call elevator_exit_icq_fn() While updating locking, b2efa05265 "block, cfq: unlink cfq_io_context's immediately" moved elevator_exit_icq_fn() invocation from exit_io_context() to the final ioc put. While this doesn't cause catastrophic failure, it effectively removes task exit notification to elevator and cause noticeable IO performance degradation with CFQ. On task exit, CFQ used to immediately expire the slice if it was being used by the exiting task as no more IO would be issued by the task; however, after b2efa05265, the notification is lost and disk could sit idle needlessly, leading to noticeable IO performance degradation for certain workloads. This patch renames ioc_exit_icq() to ioc_destroy_icq(), separates elevator_exit_icq_fn() invocation into ioc_exit_icq() and invokes it from exit_io_context(). ICQ_EXITED flag is added to avoid invoking the callback more than once for the same icq. Walking icq_list from ioc side and invoking elevator callback requires reverse double locking. This may be better implemented using RCU; unfortunately, using RCU isn't trivial. e.g. RCU protection would need to cover request_queue and queue_lock switch on cleanup makes grabbing queue_lock from RCU unsafe. Reverse double locking should do, at least for now. Signed-off-by: Tejun Heo <tj@kernel.org> Reported-and-bisected-by: Shaohua Li <shli@kernel.org> LKML-Reference: <CANejiEVzs=pUhQSTvUppkDcc2TNZyfohBRLygW5zFmXyk5A-xQ@mail.gmail.com> Tested-by: Shaohua Li <shaohua.li@intel.com> Signed-off-by: Jens Axboe <axboe@kernel.dk>
2012-02-15 08:45:53 +00:00
static void ioc_destroy_icq(struct io_cq *icq)
{
struct io_context *ioc = icq->ioc;
struct request_queue *q = icq->q;
struct elevator_type *et = q->elevator->type;
lockdep_assert_held(&ioc->lock);
radix_tree_delete(&ioc->icq_tree, icq->q->id);
hlist_del_init(&icq->ioc_node);
list_del_init(&icq->q_node);
/*
* Both setting lookup hint to and clearing it from @icq are done
* under queue_lock. If it's not pointing to @icq now, it never
* will. Hint assignment itself can race safely.
*/
if (rcu_access_pointer(ioc->icq_hint) == icq)
rcu_assign_pointer(ioc->icq_hint, NULL);
block: exit_io_context() should call elevator_exit_icq_fn() While updating locking, b2efa05265 "block, cfq: unlink cfq_io_context's immediately" moved elevator_exit_icq_fn() invocation from exit_io_context() to the final ioc put. While this doesn't cause catastrophic failure, it effectively removes task exit notification to elevator and cause noticeable IO performance degradation with CFQ. On task exit, CFQ used to immediately expire the slice if it was being used by the exiting task as no more IO would be issued by the task; however, after b2efa05265, the notification is lost and disk could sit idle needlessly, leading to noticeable IO performance degradation for certain workloads. This patch renames ioc_exit_icq() to ioc_destroy_icq(), separates elevator_exit_icq_fn() invocation into ioc_exit_icq() and invokes it from exit_io_context(). ICQ_EXITED flag is added to avoid invoking the callback more than once for the same icq. Walking icq_list from ioc side and invoking elevator callback requires reverse double locking. This may be better implemented using RCU; unfortunately, using RCU isn't trivial. e.g. RCU protection would need to cover request_queue and queue_lock switch on cleanup makes grabbing queue_lock from RCU unsafe. Reverse double locking should do, at least for now. Signed-off-by: Tejun Heo <tj@kernel.org> Reported-and-bisected-by: Shaohua Li <shli@kernel.org> LKML-Reference: <CANejiEVzs=pUhQSTvUppkDcc2TNZyfohBRLygW5zFmXyk5A-xQ@mail.gmail.com> Tested-by: Shaohua Li <shaohua.li@intel.com> Signed-off-by: Jens Axboe <axboe@kernel.dk>
2012-02-15 08:45:53 +00:00
ioc_exit_icq(icq);
/*
* @icq->q might have gone away by the time RCU callback runs
* making it impossible to determine icq_cache. Record it in @icq.
*/
icq->__rcu_icq_cache = et->icq_cache;
block: Fix use-after-free issue accessing struct io_cq There is a potential race between ioc_release_fn() and ioc_clear_queue() as shown below, due to which below kernel crash is observed. It also can result into use-after-free issue. context#1: context#2: ioc_release_fn() __ioc_clear_queue() gets the same icq ->spin_lock(&ioc->lock); ->spin_lock(&ioc->lock); ->ioc_destroy_icq(icq); ->list_del_init(&icq->q_node); ->call_rcu(&icq->__rcu_head, icq_free_icq_rcu); ->spin_unlock(&ioc->lock); ->ioc_destroy_icq(icq); ->hlist_del_init(&icq->ioc_node); This results into below crash as this memory is now used by icq->__rcu_head in context#1. There is a chance that icq could be free'd as well. 22150.386550: <6> Unable to handle kernel write to read-only memory at virtual address ffffffaa8d31ca50 ... Call trace: 22150.607350: <2> ioc_destroy_icq+0x44/0x110 22150.611202: <2> ioc_clear_queue+0xac/0x148 22150.615056: <2> blk_cleanup_queue+0x11c/0x1a0 22150.619174: <2> __scsi_remove_device+0xdc/0x128 22150.623465: <2> scsi_forget_host+0x2c/0x78 22150.627315: <2> scsi_remove_host+0x7c/0x2a0 22150.631257: <2> usb_stor_disconnect+0x74/0xc8 22150.635371: <2> usb_unbind_interface+0xc8/0x278 22150.639665: <2> device_release_driver_internal+0x198/0x250 22150.644897: <2> device_release_driver+0x24/0x30 22150.649176: <2> bus_remove_device+0xec/0x140 22150.653204: <2> device_del+0x270/0x460 22150.656712: <2> usb_disable_device+0x120/0x390 22150.660918: <2> usb_disconnect+0xf4/0x2e0 22150.664684: <2> hub_event+0xd70/0x17e8 22150.668197: <2> process_one_work+0x210/0x480 22150.672222: <2> worker_thread+0x32c/0x4c8 Fix this by adding a new ICQ_DESTROYED flag in ioc_destroy_icq() to indicate this icq is once marked as destroyed. Also, ensure __ioc_clear_queue() is accessing icq within rcu_read_lock/unlock so that icq doesn't get free'd up while it is still using it. Signed-off-by: Sahitya Tummala <stummala@codeaurora.org> Co-developed-by: Pradeep P V K <ppvk@codeaurora.org> Signed-off-by: Pradeep P V K <ppvk@codeaurora.org> Signed-off-by: Jens Axboe <axboe@kernel.dk>
2020-03-11 10:37:50 +00:00
icq->flags |= ICQ_DESTROYED;
call_rcu(&icq->__rcu_head, icq_free_icq_rcu);
}
block, cfq: unlink cfq_io_context's immediately cic is association between io_context and request_queue. A cic is linked from both ioc and q and should be destroyed when either one goes away. As ioc and q both have their own locks, locking becomes a bit complex - both orders work for removal from one but not from the other. Currently, cfq tries to circumvent this locking order issue with RCU. ioc->lock nests inside queue_lock but the radix tree and cic's are also protected by RCU allowing either side to walk their lists without grabbing lock. This rather unconventional use of RCU quickly devolves into extremely fragile convolution. e.g. The following is from cfqd going away too soon after ioc and q exits raced. general protection fault: 0000 [#1] PREEMPT SMP CPU 2 Modules linked in: [ 88.503444] Pid: 599, comm: hexdump Not tainted 3.1.0-rc10-work+ #158 Bochs Bochs RIP: 0010:[<ffffffff81397628>] [<ffffffff81397628>] cfq_exit_single_io_context+0x58/0xf0 ... Call Trace: [<ffffffff81395a4a>] call_for_each_cic+0x5a/0x90 [<ffffffff81395ab5>] cfq_exit_io_context+0x15/0x20 [<ffffffff81389130>] exit_io_context+0x100/0x140 [<ffffffff81098a29>] do_exit+0x579/0x850 [<ffffffff81098d5b>] do_group_exit+0x5b/0xd0 [<ffffffff81098de7>] sys_exit_group+0x17/0x20 [<ffffffff81b02f2b>] system_call_fastpath+0x16/0x1b The only real hot path here is cic lookup during request initialization and avoiding extra locking requires very confined use of RCU. This patch makes cic removal from both ioc and request_queue perform double-locking and unlink immediately. * From q side, the change is almost trivial as ioc->lock nests inside queue_lock. It just needs to grab each ioc->lock as it walks cic_list and unlink it. * From ioc side, it's a bit more difficult because of inversed lock order. ioc needs its lock to walk its cic_list but can't grab the matching queue_lock and needs to perform unlock-relock dancing. Unlinking is now wholly done from put_io_context() and fast path is optimized by using the queue_lock the caller already holds, which is by far the most common case. If the ioc accessed multiple devices, it tries with trylock. In unlikely cases of fast path failure, it falls back to full double-locking dance from workqueue. Double-locking isn't the prettiest thing in the world but it's *far* simpler and more understandable than RCU trick without adding any meaningful overhead. This still leaves a lot of now unnecessary RCU logics. Future patches will trim them. -v2: Vivek pointed out that cic->q was being dereferenced after cic->release() was called. Updated to use local variable @this_q instead. Signed-off-by: Tejun Heo <tj@kernel.org> Cc: Vivek Goyal <vgoyal@redhat.com> Signed-off-by: Jens Axboe <axboe@kernel.dk>
2011-12-13 23:33:39 +00:00
/*
* Slow path for ioc release in put_io_context(). Performs double-lock
* dancing to unlink all icq's and then frees ioc.
block, cfq: unlink cfq_io_context's immediately cic is association between io_context and request_queue. A cic is linked from both ioc and q and should be destroyed when either one goes away. As ioc and q both have their own locks, locking becomes a bit complex - both orders work for removal from one but not from the other. Currently, cfq tries to circumvent this locking order issue with RCU. ioc->lock nests inside queue_lock but the radix tree and cic's are also protected by RCU allowing either side to walk their lists without grabbing lock. This rather unconventional use of RCU quickly devolves into extremely fragile convolution. e.g. The following is from cfqd going away too soon after ioc and q exits raced. general protection fault: 0000 [#1] PREEMPT SMP CPU 2 Modules linked in: [ 88.503444] Pid: 599, comm: hexdump Not tainted 3.1.0-rc10-work+ #158 Bochs Bochs RIP: 0010:[<ffffffff81397628>] [<ffffffff81397628>] cfq_exit_single_io_context+0x58/0xf0 ... Call Trace: [<ffffffff81395a4a>] call_for_each_cic+0x5a/0x90 [<ffffffff81395ab5>] cfq_exit_io_context+0x15/0x20 [<ffffffff81389130>] exit_io_context+0x100/0x140 [<ffffffff81098a29>] do_exit+0x579/0x850 [<ffffffff81098d5b>] do_group_exit+0x5b/0xd0 [<ffffffff81098de7>] sys_exit_group+0x17/0x20 [<ffffffff81b02f2b>] system_call_fastpath+0x16/0x1b The only real hot path here is cic lookup during request initialization and avoiding extra locking requires very confined use of RCU. This patch makes cic removal from both ioc and request_queue perform double-locking and unlink immediately. * From q side, the change is almost trivial as ioc->lock nests inside queue_lock. It just needs to grab each ioc->lock as it walks cic_list and unlink it. * From ioc side, it's a bit more difficult because of inversed lock order. ioc needs its lock to walk its cic_list but can't grab the matching queue_lock and needs to perform unlock-relock dancing. Unlinking is now wholly done from put_io_context() and fast path is optimized by using the queue_lock the caller already holds, which is by far the most common case. If the ioc accessed multiple devices, it tries with trylock. In unlikely cases of fast path failure, it falls back to full double-locking dance from workqueue. Double-locking isn't the prettiest thing in the world but it's *far* simpler and more understandable than RCU trick without adding any meaningful overhead. This still leaves a lot of now unnecessary RCU logics. Future patches will trim them. -v2: Vivek pointed out that cic->q was being dereferenced after cic->release() was called. Updated to use local variable @this_q instead. Signed-off-by: Tejun Heo <tj@kernel.org> Cc: Vivek Goyal <vgoyal@redhat.com> Signed-off-by: Jens Axboe <axboe@kernel.dk>
2011-12-13 23:33:39 +00:00
*/
static void ioc_release_fn(struct work_struct *work)
{
block, cfq: unlink cfq_io_context's immediately cic is association between io_context and request_queue. A cic is linked from both ioc and q and should be destroyed when either one goes away. As ioc and q both have their own locks, locking becomes a bit complex - both orders work for removal from one but not from the other. Currently, cfq tries to circumvent this locking order issue with RCU. ioc->lock nests inside queue_lock but the radix tree and cic's are also protected by RCU allowing either side to walk their lists without grabbing lock. This rather unconventional use of RCU quickly devolves into extremely fragile convolution. e.g. The following is from cfqd going away too soon after ioc and q exits raced. general protection fault: 0000 [#1] PREEMPT SMP CPU 2 Modules linked in: [ 88.503444] Pid: 599, comm: hexdump Not tainted 3.1.0-rc10-work+ #158 Bochs Bochs RIP: 0010:[<ffffffff81397628>] [<ffffffff81397628>] cfq_exit_single_io_context+0x58/0xf0 ... Call Trace: [<ffffffff81395a4a>] call_for_each_cic+0x5a/0x90 [<ffffffff81395ab5>] cfq_exit_io_context+0x15/0x20 [<ffffffff81389130>] exit_io_context+0x100/0x140 [<ffffffff81098a29>] do_exit+0x579/0x850 [<ffffffff81098d5b>] do_group_exit+0x5b/0xd0 [<ffffffff81098de7>] sys_exit_group+0x17/0x20 [<ffffffff81b02f2b>] system_call_fastpath+0x16/0x1b The only real hot path here is cic lookup during request initialization and avoiding extra locking requires very confined use of RCU. This patch makes cic removal from both ioc and request_queue perform double-locking and unlink immediately. * From q side, the change is almost trivial as ioc->lock nests inside queue_lock. It just needs to grab each ioc->lock as it walks cic_list and unlink it. * From ioc side, it's a bit more difficult because of inversed lock order. ioc needs its lock to walk its cic_list but can't grab the matching queue_lock and needs to perform unlock-relock dancing. Unlinking is now wholly done from put_io_context() and fast path is optimized by using the queue_lock the caller already holds, which is by far the most common case. If the ioc accessed multiple devices, it tries with trylock. In unlikely cases of fast path failure, it falls back to full double-locking dance from workqueue. Double-locking isn't the prettiest thing in the world but it's *far* simpler and more understandable than RCU trick without adding any meaningful overhead. This still leaves a lot of now unnecessary RCU logics. Future patches will trim them. -v2: Vivek pointed out that cic->q was being dereferenced after cic->release() was called. Updated to use local variable @this_q instead. Signed-off-by: Tejun Heo <tj@kernel.org> Cc: Vivek Goyal <vgoyal@redhat.com> Signed-off-by: Jens Axboe <axboe@kernel.dk>
2011-12-13 23:33:39 +00:00
struct io_context *ioc = container_of(work, struct io_context,
release_work);
spin_lock_irq(&ioc->lock);
block, cfq: unlink cfq_io_context's immediately cic is association between io_context and request_queue. A cic is linked from both ioc and q and should be destroyed when either one goes away. As ioc and q both have their own locks, locking becomes a bit complex - both orders work for removal from one but not from the other. Currently, cfq tries to circumvent this locking order issue with RCU. ioc->lock nests inside queue_lock but the radix tree and cic's are also protected by RCU allowing either side to walk their lists without grabbing lock. This rather unconventional use of RCU quickly devolves into extremely fragile convolution. e.g. The following is from cfqd going away too soon after ioc and q exits raced. general protection fault: 0000 [#1] PREEMPT SMP CPU 2 Modules linked in: [ 88.503444] Pid: 599, comm: hexdump Not tainted 3.1.0-rc10-work+ #158 Bochs Bochs RIP: 0010:[<ffffffff81397628>] [<ffffffff81397628>] cfq_exit_single_io_context+0x58/0xf0 ... Call Trace: [<ffffffff81395a4a>] call_for_each_cic+0x5a/0x90 [<ffffffff81395ab5>] cfq_exit_io_context+0x15/0x20 [<ffffffff81389130>] exit_io_context+0x100/0x140 [<ffffffff81098a29>] do_exit+0x579/0x850 [<ffffffff81098d5b>] do_group_exit+0x5b/0xd0 [<ffffffff81098de7>] sys_exit_group+0x17/0x20 [<ffffffff81b02f2b>] system_call_fastpath+0x16/0x1b The only real hot path here is cic lookup during request initialization and avoiding extra locking requires very confined use of RCU. This patch makes cic removal from both ioc and request_queue perform double-locking and unlink immediately. * From q side, the change is almost trivial as ioc->lock nests inside queue_lock. It just needs to grab each ioc->lock as it walks cic_list and unlink it. * From ioc side, it's a bit more difficult because of inversed lock order. ioc needs its lock to walk its cic_list but can't grab the matching queue_lock and needs to perform unlock-relock dancing. Unlinking is now wholly done from put_io_context() and fast path is optimized by using the queue_lock the caller already holds, which is by far the most common case. If the ioc accessed multiple devices, it tries with trylock. In unlikely cases of fast path failure, it falls back to full double-locking dance from workqueue. Double-locking isn't the prettiest thing in the world but it's *far* simpler and more understandable than RCU trick without adding any meaningful overhead. This still leaves a lot of now unnecessary RCU logics. Future patches will trim them. -v2: Vivek pointed out that cic->q was being dereferenced after cic->release() was called. Updated to use local variable @this_q instead. Signed-off-by: Tejun Heo <tj@kernel.org> Cc: Vivek Goyal <vgoyal@redhat.com> Signed-off-by: Jens Axboe <axboe@kernel.dk>
2011-12-13 23:33:39 +00:00
while (!hlist_empty(&ioc->icq_list)) {
struct io_cq *icq = hlist_entry(ioc->icq_list.first,
struct io_cq, ioc_node);
struct request_queue *q = icq->q;
if (spin_trylock(&q->queue_lock)) {
block: exit_io_context() should call elevator_exit_icq_fn() While updating locking, b2efa05265 "block, cfq: unlink cfq_io_context's immediately" moved elevator_exit_icq_fn() invocation from exit_io_context() to the final ioc put. While this doesn't cause catastrophic failure, it effectively removes task exit notification to elevator and cause noticeable IO performance degradation with CFQ. On task exit, CFQ used to immediately expire the slice if it was being used by the exiting task as no more IO would be issued by the task; however, after b2efa05265, the notification is lost and disk could sit idle needlessly, leading to noticeable IO performance degradation for certain workloads. This patch renames ioc_exit_icq() to ioc_destroy_icq(), separates elevator_exit_icq_fn() invocation into ioc_exit_icq() and invokes it from exit_io_context(). ICQ_EXITED flag is added to avoid invoking the callback more than once for the same icq. Walking icq_list from ioc side and invoking elevator callback requires reverse double locking. This may be better implemented using RCU; unfortunately, using RCU isn't trivial. e.g. RCU protection would need to cover request_queue and queue_lock switch on cleanup makes grabbing queue_lock from RCU unsafe. Reverse double locking should do, at least for now. Signed-off-by: Tejun Heo <tj@kernel.org> Reported-and-bisected-by: Shaohua Li <shli@kernel.org> LKML-Reference: <CANejiEVzs=pUhQSTvUppkDcc2TNZyfohBRLygW5zFmXyk5A-xQ@mail.gmail.com> Tested-by: Shaohua Li <shaohua.li@intel.com> Signed-off-by: Jens Axboe <axboe@kernel.dk>
2012-02-15 08:45:53 +00:00
ioc_destroy_icq(icq);
spin_unlock(&q->queue_lock);
} else {
/* Make sure q and icq cannot be freed. */
rcu_read_lock();
/* Re-acquire the locks in the correct order. */
spin_unlock(&ioc->lock);
spin_lock(&q->queue_lock);
spin_lock(&ioc->lock);
/*
* The icq may have been destroyed when the ioc lock
* was released.
*/
if (!(icq->flags & ICQ_DESTROYED))
ioc_destroy_icq(icq);
spin_unlock(&q->queue_lock);
rcu_read_unlock();
block, cfq: unlink cfq_io_context's immediately cic is association between io_context and request_queue. A cic is linked from both ioc and q and should be destroyed when either one goes away. As ioc and q both have their own locks, locking becomes a bit complex - both orders work for removal from one but not from the other. Currently, cfq tries to circumvent this locking order issue with RCU. ioc->lock nests inside queue_lock but the radix tree and cic's are also protected by RCU allowing either side to walk their lists without grabbing lock. This rather unconventional use of RCU quickly devolves into extremely fragile convolution. e.g. The following is from cfqd going away too soon after ioc and q exits raced. general protection fault: 0000 [#1] PREEMPT SMP CPU 2 Modules linked in: [ 88.503444] Pid: 599, comm: hexdump Not tainted 3.1.0-rc10-work+ #158 Bochs Bochs RIP: 0010:[<ffffffff81397628>] [<ffffffff81397628>] cfq_exit_single_io_context+0x58/0xf0 ... Call Trace: [<ffffffff81395a4a>] call_for_each_cic+0x5a/0x90 [<ffffffff81395ab5>] cfq_exit_io_context+0x15/0x20 [<ffffffff81389130>] exit_io_context+0x100/0x140 [<ffffffff81098a29>] do_exit+0x579/0x850 [<ffffffff81098d5b>] do_group_exit+0x5b/0xd0 [<ffffffff81098de7>] sys_exit_group+0x17/0x20 [<ffffffff81b02f2b>] system_call_fastpath+0x16/0x1b The only real hot path here is cic lookup during request initialization and avoiding extra locking requires very confined use of RCU. This patch makes cic removal from both ioc and request_queue perform double-locking and unlink immediately. * From q side, the change is almost trivial as ioc->lock nests inside queue_lock. It just needs to grab each ioc->lock as it walks cic_list and unlink it. * From ioc side, it's a bit more difficult because of inversed lock order. ioc needs its lock to walk its cic_list but can't grab the matching queue_lock and needs to perform unlock-relock dancing. Unlinking is now wholly done from put_io_context() and fast path is optimized by using the queue_lock the caller already holds, which is by far the most common case. If the ioc accessed multiple devices, it tries with trylock. In unlikely cases of fast path failure, it falls back to full double-locking dance from workqueue. Double-locking isn't the prettiest thing in the world but it's *far* simpler and more understandable than RCU trick without adding any meaningful overhead. This still leaves a lot of now unnecessary RCU logics. Future patches will trim them. -v2: Vivek pointed out that cic->q was being dereferenced after cic->release() was called. Updated to use local variable @this_q instead. Signed-off-by: Tejun Heo <tj@kernel.org> Cc: Vivek Goyal <vgoyal@redhat.com> Signed-off-by: Jens Axboe <axboe@kernel.dk>
2011-12-13 23:33:39 +00:00
}
}
spin_unlock_irq(&ioc->lock);
block, cfq: unlink cfq_io_context's immediately cic is association between io_context and request_queue. A cic is linked from both ioc and q and should be destroyed when either one goes away. As ioc and q both have their own locks, locking becomes a bit complex - both orders work for removal from one but not from the other. Currently, cfq tries to circumvent this locking order issue with RCU. ioc->lock nests inside queue_lock but the radix tree and cic's are also protected by RCU allowing either side to walk their lists without grabbing lock. This rather unconventional use of RCU quickly devolves into extremely fragile convolution. e.g. The following is from cfqd going away too soon after ioc and q exits raced. general protection fault: 0000 [#1] PREEMPT SMP CPU 2 Modules linked in: [ 88.503444] Pid: 599, comm: hexdump Not tainted 3.1.0-rc10-work+ #158 Bochs Bochs RIP: 0010:[<ffffffff81397628>] [<ffffffff81397628>] cfq_exit_single_io_context+0x58/0xf0 ... Call Trace: [<ffffffff81395a4a>] call_for_each_cic+0x5a/0x90 [<ffffffff81395ab5>] cfq_exit_io_context+0x15/0x20 [<ffffffff81389130>] exit_io_context+0x100/0x140 [<ffffffff81098a29>] do_exit+0x579/0x850 [<ffffffff81098d5b>] do_group_exit+0x5b/0xd0 [<ffffffff81098de7>] sys_exit_group+0x17/0x20 [<ffffffff81b02f2b>] system_call_fastpath+0x16/0x1b The only real hot path here is cic lookup during request initialization and avoiding extra locking requires very confined use of RCU. This patch makes cic removal from both ioc and request_queue perform double-locking and unlink immediately. * From q side, the change is almost trivial as ioc->lock nests inside queue_lock. It just needs to grab each ioc->lock as it walks cic_list and unlink it. * From ioc side, it's a bit more difficult because of inversed lock order. ioc needs its lock to walk its cic_list but can't grab the matching queue_lock and needs to perform unlock-relock dancing. Unlinking is now wholly done from put_io_context() and fast path is optimized by using the queue_lock the caller already holds, which is by far the most common case. If the ioc accessed multiple devices, it tries with trylock. In unlikely cases of fast path failure, it falls back to full double-locking dance from workqueue. Double-locking isn't the prettiest thing in the world but it's *far* simpler and more understandable than RCU trick without adding any meaningful overhead. This still leaves a lot of now unnecessary RCU logics. Future patches will trim them. -v2: Vivek pointed out that cic->q was being dereferenced after cic->release() was called. Updated to use local variable @this_q instead. Signed-off-by: Tejun Heo <tj@kernel.org> Cc: Vivek Goyal <vgoyal@redhat.com> Signed-off-by: Jens Axboe <axboe@kernel.dk>
2011-12-13 23:33:39 +00:00
kmem_cache_free(iocontext_cachep, ioc);
}
/*
* Releasing icqs requires reverse order double locking and we may already be
* holding a queue_lock. Do it asynchronously from a workqueue.
*/
static bool ioc_delay_free(struct io_context *ioc)
{
unsigned long flags;
spin_lock_irqsave(&ioc->lock, flags);
if (!hlist_empty(&ioc->icq_list)) {
queue_work(system_power_efficient_wq, &ioc->release_work);
spin_unlock_irqrestore(&ioc->lock, flags);
return true;
}
spin_unlock_irqrestore(&ioc->lock, flags);
return false;
}
/**
* ioc_clear_queue - break any ioc association with the specified queue
* @q: request_queue being cleared
*
* Walk @q->icq_list and exit all io_cq's.
*/
void ioc_clear_queue(struct request_queue *q)
{
LIST_HEAD(icq_list);
spin_lock_irq(&q->queue_lock);
list_splice_init(&q->icq_list, &icq_list);
spin_unlock_irq(&q->queue_lock);
rcu_read_lock();
while (!list_empty(&icq_list)) {
struct io_cq *icq =
list_entry(icq_list.next, struct io_cq, q_node);
spin_lock_irq(&icq->ioc->lock);
if (!(icq->flags & ICQ_DESTROYED))
ioc_destroy_icq(icq);
spin_unlock_irq(&icq->ioc->lock);
}
rcu_read_unlock();
}
#else /* CONFIG_BLK_ICQ */
static inline void ioc_exit_icqs(struct io_context *ioc)
{
}
static inline bool ioc_delay_free(struct io_context *ioc)
{
return false;
}
#endif /* CONFIG_BLK_ICQ */
/**
* put_io_context - put a reference of io_context
* @ioc: io_context to put
*
* Decrement reference count of @ioc and release it if the count reaches
* zero.
*/
void put_io_context(struct io_context *ioc)
{
BUG_ON(atomic_long_read(&ioc->refcount) <= 0);
if (atomic_long_dec_and_test(&ioc->refcount) && !ioc_delay_free(ioc))
kmem_cache_free(iocontext_cachep, ioc);
}
EXPORT_SYMBOL_GPL(put_io_context);
/* Called by the exiting task */
void exit_io_context(struct task_struct *task)
{
struct io_context *ioc;
task_lock(task);
ioc = task->io_context;
task->io_context = NULL;
task_unlock(task);
if (atomic_dec_and_test(&ioc->active_ref)) {
ioc_exit_icqs(ioc);
put_io_context(ioc);
}
}
static struct io_context *alloc_io_context(gfp_t gfp_flags, int node)
{
struct io_context *ioc;
ioc = kmem_cache_alloc_node(iocontext_cachep, gfp_flags | __GFP_ZERO,
node);
if (unlikely(!ioc))
return NULL;
atomic_long_set(&ioc->refcount, 1);
atomic_set(&ioc->active_ref, 1);
#ifdef CONFIG_BLK_ICQ
spin_lock_init(&ioc->lock);
INIT_RADIX_TREE(&ioc->icq_tree, GFP_ATOMIC);
INIT_HLIST_HEAD(&ioc->icq_list);
block, cfq: unlink cfq_io_context's immediately cic is association between io_context and request_queue. A cic is linked from both ioc and q and should be destroyed when either one goes away. As ioc and q both have their own locks, locking becomes a bit complex - both orders work for removal from one but not from the other. Currently, cfq tries to circumvent this locking order issue with RCU. ioc->lock nests inside queue_lock but the radix tree and cic's are also protected by RCU allowing either side to walk their lists without grabbing lock. This rather unconventional use of RCU quickly devolves into extremely fragile convolution. e.g. The following is from cfqd going away too soon after ioc and q exits raced. general protection fault: 0000 [#1] PREEMPT SMP CPU 2 Modules linked in: [ 88.503444] Pid: 599, comm: hexdump Not tainted 3.1.0-rc10-work+ #158 Bochs Bochs RIP: 0010:[<ffffffff81397628>] [<ffffffff81397628>] cfq_exit_single_io_context+0x58/0xf0 ... Call Trace: [<ffffffff81395a4a>] call_for_each_cic+0x5a/0x90 [<ffffffff81395ab5>] cfq_exit_io_context+0x15/0x20 [<ffffffff81389130>] exit_io_context+0x100/0x140 [<ffffffff81098a29>] do_exit+0x579/0x850 [<ffffffff81098d5b>] do_group_exit+0x5b/0xd0 [<ffffffff81098de7>] sys_exit_group+0x17/0x20 [<ffffffff81b02f2b>] system_call_fastpath+0x16/0x1b The only real hot path here is cic lookup during request initialization and avoiding extra locking requires very confined use of RCU. This patch makes cic removal from both ioc and request_queue perform double-locking and unlink immediately. * From q side, the change is almost trivial as ioc->lock nests inside queue_lock. It just needs to grab each ioc->lock as it walks cic_list and unlink it. * From ioc side, it's a bit more difficult because of inversed lock order. ioc needs its lock to walk its cic_list but can't grab the matching queue_lock and needs to perform unlock-relock dancing. Unlinking is now wholly done from put_io_context() and fast path is optimized by using the queue_lock the caller already holds, which is by far the most common case. If the ioc accessed multiple devices, it tries with trylock. In unlikely cases of fast path failure, it falls back to full double-locking dance from workqueue. Double-locking isn't the prettiest thing in the world but it's *far* simpler and more understandable than RCU trick without adding any meaningful overhead. This still leaves a lot of now unnecessary RCU logics. Future patches will trim them. -v2: Vivek pointed out that cic->q was being dereferenced after cic->release() was called. Updated to use local variable @this_q instead. Signed-off-by: Tejun Heo <tj@kernel.org> Cc: Vivek Goyal <vgoyal@redhat.com> Signed-off-by: Jens Axboe <axboe@kernel.dk>
2011-12-13 23:33:39 +00:00
INIT_WORK(&ioc->release_work, ioc_release_fn);
#endif
block: fix default IO priority handling again Commit e70344c05995 ("block: fix default IO priority handling") introduced an inconsistency in get_current_ioprio() that tasks without IO context return IOPRIO_DEFAULT priority while tasks with freshly allocated IO context will return 0 (IOPRIO_CLASS_NONE/0) IO priority. Tasks without IO context used to be rare before 5a9d041ba2f6 ("block: move io_context creation into where it's needed") but after this commit they became common because now only BFQ IO scheduler setups task's IO context. Similar inconsistency is there for get_task_ioprio() so this inconsistency is now exposed to userspace and userspace will see different IO priority for tasks operating on devices with BFQ compared to devices without BFQ. Furthemore the changes done by commit e70344c05995 change the behavior when no IO priority is set for BFQ IO scheduler which is also documented in ioprio_set(2) manpage: "If no I/O scheduler has been set for a thread, then by default the I/O priority will follow the CPU nice value (setpriority(2)). In Linux kernels before version 2.6.24, once an I/O priority had been set using ioprio_set(), there was no way to reset the I/O scheduling behavior to the default. Since Linux 2.6.24, specifying ioprio as 0 can be used to reset to the default I/O scheduling behavior." So make sure we default to IOPRIO_CLASS_NONE as used to be the case before commit e70344c05995. Also cleanup alloc_io_context() to explicitely set this IO priority for the allocated IO context to avoid future surprises. Note that we tweak ioprio_best() to maintain ioprio_get(2) behavior and make this commit easily backportable. CC: stable@vger.kernel.org Fixes: e70344c05995 ("block: fix default IO priority handling") Reviewed-by: Damien Le Moal <damien.lemoal@opensource.wdc.com> Tested-by: Damien Le Moal <damien.lemoal@opensource.wdc.com> Signed-off-by: Jan Kara <jack@suse.cz> Reviewed-by: Christoph Hellwig <hch@lst.de> Link: https://lore.kernel.org/r/20220623074840.5960-1-jack@suse.cz Signed-off-by: Jens Axboe <axboe@kernel.dk>
2022-06-23 07:48:26 +00:00
ioc->ioprio = IOPRIO_DEFAULT;
return ioc;
}
int set_task_ioprio(struct task_struct *task, int ioprio)
{
int err;
const struct cred *cred = current_cred(), *tcred;
rcu_read_lock();
tcred = __task_cred(task);
if (!uid_eq(tcred->uid, cred->euid) &&
!uid_eq(tcred->uid, cred->uid) && !capable(CAP_SYS_NICE)) {
rcu_read_unlock();
return -EPERM;
}
rcu_read_unlock();
err = security_task_setioprio(task, ioprio);
if (err)
return err;
task_lock(task);
if (unlikely(!task->io_context)) {
struct io_context *ioc;
task_unlock(task);
ioc = alloc_io_context(GFP_ATOMIC, NUMA_NO_NODE);
if (!ioc)
return -ENOMEM;
task_lock(task);
if (task->flags & PF_EXITING) {
kmem_cache_free(iocontext_cachep, ioc);
goto out;
}
if (task->io_context)
kmem_cache_free(iocontext_cachep, ioc);
else
task->io_context = ioc;
}
task->io_context->ioprio = ioprio;
out:
task_unlock(task);
block: restore the old set_task_ioprio() behaviour wrt PF_EXITING PF_EXITING tasks were silently ignored before the below commits. Continue doing so. Otherwise python-psutil tests fail: ERROR: psutil.tests.test_process.TestProcess.test_zombie_process ---------------------------------------------------------------------- Traceback (most recent call last): File "/home/abuild/rpmbuild/BUILD/psutil-5.9.0/build/lib.linux-x86_64-3.9/psutil/_pslinux.py", line 1661, in wrapper return fun(self, *args, **kwargs) File "/home/abuild/rpmbuild/BUILD/psutil-5.9.0/build/lib.linux-x86_64-3.9/psutil/_pslinux.py", line 2133, in ionice_set return cext.proc_ioprio_set(self.pid, ioclass, value) ProcessLookupError: [Errno 3] No such process During handling of the above exception, another exception occurred: Traceback (most recent call last): File "/home/abuild/rpmbuild/BUILD/psutil-5.9.0/psutil/tests/test_process.py", line 1313, in test_zombie_process succeed_or_zombie_p_exc(fun) File "/home/abuild/rpmbuild/BUILD/psutil-5.9.0/psutil/tests/test_process.py", line 1288, in succeed_or_zombie_p_exc return fun() File "/home/abuild/rpmbuild/BUILD/psutil-5.9.0/build/lib.linux-x86_64-3.9/psutil/__init__.py", line 792, in ionice return self._proc.ionice_set(ioclass, value) File "/home/abuild/rpmbuild/BUILD/psutil-5.9.0/build/lib.linux-x86_64-3.9/psutil/_pslinux.py", line 1665, in wrapper raise NoSuchProcess(self.pid, self._name) psutil.NoSuchProcess: process no longer exists (pid=2057) Cc: Christoph Hellwig <hch@lst.de> Cc: Jan Kara <jack@suse.cz> Cc: Jens Axboe <axboe@kernel.dk> Fixes: 5fc11eebb4 (block: open code create_task_io_context in set_task_ioprio) Fixes: a957b61254 (block: fix error in handling dead task for ioprio setting) Signed-off-by: Jiri Slaby <jslaby@suse.cz> Reviewed-by: Jan Kara <jack@suse.cz> Link: https://lore.kernel.org/r/20220328085928.7899-1-jslaby@suse.cz Signed-off-by: Jens Axboe <axboe@kernel.dk>
2022-03-28 08:59:28 +00:00
return 0;
}
EXPORT_SYMBOL_GPL(set_task_ioprio);
int __copy_io(unsigned long clone_flags, struct task_struct *tsk)
{
struct io_context *ioc = current->io_context;
/*
* Share io context with parent, if CLONE_IO is set
*/
if (clone_flags & CLONE_IO) {
atomic_inc(&ioc->active_ref);
tsk->io_context = ioc;
} else if (ioprio_valid(ioc->ioprio)) {
tsk->io_context = alloc_io_context(GFP_KERNEL, NUMA_NO_NODE);
if (!tsk->io_context)
return -ENOMEM;
tsk->io_context->ioprio = ioc->ioprio;
}
return 0;
}
#ifdef CONFIG_BLK_ICQ
/**
* ioc_lookup_icq - lookup io_cq from ioc
* @q: the associated request_queue
*
* Look up io_cq associated with @ioc - @q pair from @ioc. Must be called
* with @q->queue_lock held.
*/
struct io_cq *ioc_lookup_icq(struct request_queue *q)
{
struct io_context *ioc = current->io_context;
struct io_cq *icq;
lockdep_assert_held(&q->queue_lock);
/*
* icq's are indexed from @ioc using radix tree and hint pointer,
* both of which are protected with RCU. All removals are done
* holding both q and ioc locks, and we're holding q lock - if we
* find a icq which points to us, it's guaranteed to be valid.
*/
rcu_read_lock();
icq = rcu_dereference(ioc->icq_hint);
if (icq && icq->q == q)
goto out;
icq = radix_tree_lookup(&ioc->icq_tree, q->id);
if (icq && icq->q == q)
rcu_assign_pointer(ioc->icq_hint, icq); /* allowed to race */
else
icq = NULL;
out:
rcu_read_unlock();
return icq;
}
EXPORT_SYMBOL(ioc_lookup_icq);
block, cfq: move icq creation and rq->elv.icq association to block core Now block layer knows everything necessary to create and associate icq's with requests. Move ioc_create_icq() to blk-ioc.c and update get_request() such that, if elevator_type->icq_size is set, requests are automatically associated with their matching icq's before elv_set_request(). io_context reference is also managed by block core on request alloc/free. * Only ioprio/cgroup changed handling remains from cfq_get_cic(). Collapsed into cfq_set_request(). * This removes queue kicking on icq allocation failure (for now). As icq allocation failure is rare and the only effect of queue kicking achieved was possibily accelerating queue processing, this change shouldn't be noticeable. There is a larger underlying problem. Unlike request allocation, icq allocation is not guaranteed to succeed eventually after retries. The number of icq is unbound and thus mempool can't be the solution either. This effectively adds allocation dependency on memory free path and thus possibility of deadlock. This usually wouldn't happen because icq allocation is not a hot path and, even when the condition triggers, it's highly unlikely that none of the writeback workers already has icq. However, this is still possible especially if elevator is being switched under high memory pressure, so we better get it fixed. Probably the only solution is just bypassing elevator and appending to dispatch queue on any elevator allocation failure. * Comment added to explain how icq's are managed and synchronized. This completes cleanup of io_context interface. Signed-off-by: Tejun Heo <tj@kernel.org> Signed-off-by: Jens Axboe <axboe@kernel.dk>
2011-12-13 23:33:42 +00:00
/**
* ioc_create_icq - create and link io_cq
* @q: request_queue of interest
*
* Make sure io_cq linking @ioc and @q exists. If icq doesn't exist, they
* will be created using @gfp_mask.
block, cfq: move icq creation and rq->elv.icq association to block core Now block layer knows everything necessary to create and associate icq's with requests. Move ioc_create_icq() to blk-ioc.c and update get_request() such that, if elevator_type->icq_size is set, requests are automatically associated with their matching icq's before elv_set_request(). io_context reference is also managed by block core on request alloc/free. * Only ioprio/cgroup changed handling remains from cfq_get_cic(). Collapsed into cfq_set_request(). * This removes queue kicking on icq allocation failure (for now). As icq allocation failure is rare and the only effect of queue kicking achieved was possibily accelerating queue processing, this change shouldn't be noticeable. There is a larger underlying problem. Unlike request allocation, icq allocation is not guaranteed to succeed eventually after retries. The number of icq is unbound and thus mempool can't be the solution either. This effectively adds allocation dependency on memory free path and thus possibility of deadlock. This usually wouldn't happen because icq allocation is not a hot path and, even when the condition triggers, it's highly unlikely that none of the writeback workers already has icq. However, this is still possible especially if elevator is being switched under high memory pressure, so we better get it fixed. Probably the only solution is just bypassing elevator and appending to dispatch queue on any elevator allocation failure. * Comment added to explain how icq's are managed and synchronized. This completes cleanup of io_context interface. Signed-off-by: Tejun Heo <tj@kernel.org> Signed-off-by: Jens Axboe <axboe@kernel.dk>
2011-12-13 23:33:42 +00:00
*
* The caller is responsible for ensuring @ioc won't go away and @q is
* alive and will stay alive until this function returns.
*/
static struct io_cq *ioc_create_icq(struct request_queue *q)
block, cfq: move icq creation and rq->elv.icq association to block core Now block layer knows everything necessary to create and associate icq's with requests. Move ioc_create_icq() to blk-ioc.c and update get_request() such that, if elevator_type->icq_size is set, requests are automatically associated with their matching icq's before elv_set_request(). io_context reference is also managed by block core on request alloc/free. * Only ioprio/cgroup changed handling remains from cfq_get_cic(). Collapsed into cfq_set_request(). * This removes queue kicking on icq allocation failure (for now). As icq allocation failure is rare and the only effect of queue kicking achieved was possibily accelerating queue processing, this change shouldn't be noticeable. There is a larger underlying problem. Unlike request allocation, icq allocation is not guaranteed to succeed eventually after retries. The number of icq is unbound and thus mempool can't be the solution either. This effectively adds allocation dependency on memory free path and thus possibility of deadlock. This usually wouldn't happen because icq allocation is not a hot path and, even when the condition triggers, it's highly unlikely that none of the writeback workers already has icq. However, this is still possible especially if elevator is being switched under high memory pressure, so we better get it fixed. Probably the only solution is just bypassing elevator and appending to dispatch queue on any elevator allocation failure. * Comment added to explain how icq's are managed and synchronized. This completes cleanup of io_context interface. Signed-off-by: Tejun Heo <tj@kernel.org> Signed-off-by: Jens Axboe <axboe@kernel.dk>
2011-12-13 23:33:42 +00:00
{
struct io_context *ioc = current->io_context;
block, cfq: move icq creation and rq->elv.icq association to block core Now block layer knows everything necessary to create and associate icq's with requests. Move ioc_create_icq() to blk-ioc.c and update get_request() such that, if elevator_type->icq_size is set, requests are automatically associated with their matching icq's before elv_set_request(). io_context reference is also managed by block core on request alloc/free. * Only ioprio/cgroup changed handling remains from cfq_get_cic(). Collapsed into cfq_set_request(). * This removes queue kicking on icq allocation failure (for now). As icq allocation failure is rare and the only effect of queue kicking achieved was possibily accelerating queue processing, this change shouldn't be noticeable. There is a larger underlying problem. Unlike request allocation, icq allocation is not guaranteed to succeed eventually after retries. The number of icq is unbound and thus mempool can't be the solution either. This effectively adds allocation dependency on memory free path and thus possibility of deadlock. This usually wouldn't happen because icq allocation is not a hot path and, even when the condition triggers, it's highly unlikely that none of the writeback workers already has icq. However, this is still possible especially if elevator is being switched under high memory pressure, so we better get it fixed. Probably the only solution is just bypassing elevator and appending to dispatch queue on any elevator allocation failure. * Comment added to explain how icq's are managed and synchronized. This completes cleanup of io_context interface. Signed-off-by: Tejun Heo <tj@kernel.org> Signed-off-by: Jens Axboe <axboe@kernel.dk>
2011-12-13 23:33:42 +00:00
struct elevator_type *et = q->elevator->type;
struct io_cq *icq;
/* allocate stuff */
icq = kmem_cache_alloc_node(et->icq_cache, GFP_ATOMIC | __GFP_ZERO,
block, cfq: move icq creation and rq->elv.icq association to block core Now block layer knows everything necessary to create and associate icq's with requests. Move ioc_create_icq() to blk-ioc.c and update get_request() such that, if elevator_type->icq_size is set, requests are automatically associated with their matching icq's before elv_set_request(). io_context reference is also managed by block core on request alloc/free. * Only ioprio/cgroup changed handling remains from cfq_get_cic(). Collapsed into cfq_set_request(). * This removes queue kicking on icq allocation failure (for now). As icq allocation failure is rare and the only effect of queue kicking achieved was possibily accelerating queue processing, this change shouldn't be noticeable. There is a larger underlying problem. Unlike request allocation, icq allocation is not guaranteed to succeed eventually after retries. The number of icq is unbound and thus mempool can't be the solution either. This effectively adds allocation dependency on memory free path and thus possibility of deadlock. This usually wouldn't happen because icq allocation is not a hot path and, even when the condition triggers, it's highly unlikely that none of the writeback workers already has icq. However, this is still possible especially if elevator is being switched under high memory pressure, so we better get it fixed. Probably the only solution is just bypassing elevator and appending to dispatch queue on any elevator allocation failure. * Comment added to explain how icq's are managed and synchronized. This completes cleanup of io_context interface. Signed-off-by: Tejun Heo <tj@kernel.org> Signed-off-by: Jens Axboe <axboe@kernel.dk>
2011-12-13 23:33:42 +00:00
q->node);
if (!icq)
return NULL;
if (radix_tree_maybe_preload(GFP_ATOMIC) < 0) {
block, cfq: move icq creation and rq->elv.icq association to block core Now block layer knows everything necessary to create and associate icq's with requests. Move ioc_create_icq() to blk-ioc.c and update get_request() such that, if elevator_type->icq_size is set, requests are automatically associated with their matching icq's before elv_set_request(). io_context reference is also managed by block core on request alloc/free. * Only ioprio/cgroup changed handling remains from cfq_get_cic(). Collapsed into cfq_set_request(). * This removes queue kicking on icq allocation failure (for now). As icq allocation failure is rare and the only effect of queue kicking achieved was possibily accelerating queue processing, this change shouldn't be noticeable. There is a larger underlying problem. Unlike request allocation, icq allocation is not guaranteed to succeed eventually after retries. The number of icq is unbound and thus mempool can't be the solution either. This effectively adds allocation dependency on memory free path and thus possibility of deadlock. This usually wouldn't happen because icq allocation is not a hot path and, even when the condition triggers, it's highly unlikely that none of the writeback workers already has icq. However, this is still possible especially if elevator is being switched under high memory pressure, so we better get it fixed. Probably the only solution is just bypassing elevator and appending to dispatch queue on any elevator allocation failure. * Comment added to explain how icq's are managed and synchronized. This completes cleanup of io_context interface. Signed-off-by: Tejun Heo <tj@kernel.org> Signed-off-by: Jens Axboe <axboe@kernel.dk>
2011-12-13 23:33:42 +00:00
kmem_cache_free(et->icq_cache, icq);
return NULL;
}
icq->ioc = ioc;
icq->q = q;
INIT_LIST_HEAD(&icq->q_node);
INIT_HLIST_NODE(&icq->ioc_node);
/* lock both q and ioc and try to link @icq */
spin_lock_irq(&q->queue_lock);
block, cfq: move icq creation and rq->elv.icq association to block core Now block layer knows everything necessary to create and associate icq's with requests. Move ioc_create_icq() to blk-ioc.c and update get_request() such that, if elevator_type->icq_size is set, requests are automatically associated with their matching icq's before elv_set_request(). io_context reference is also managed by block core on request alloc/free. * Only ioprio/cgroup changed handling remains from cfq_get_cic(). Collapsed into cfq_set_request(). * This removes queue kicking on icq allocation failure (for now). As icq allocation failure is rare and the only effect of queue kicking achieved was possibily accelerating queue processing, this change shouldn't be noticeable. There is a larger underlying problem. Unlike request allocation, icq allocation is not guaranteed to succeed eventually after retries. The number of icq is unbound and thus mempool can't be the solution either. This effectively adds allocation dependency on memory free path and thus possibility of deadlock. This usually wouldn't happen because icq allocation is not a hot path and, even when the condition triggers, it's highly unlikely that none of the writeback workers already has icq. However, this is still possible especially if elevator is being switched under high memory pressure, so we better get it fixed. Probably the only solution is just bypassing elevator and appending to dispatch queue on any elevator allocation failure. * Comment added to explain how icq's are managed and synchronized. This completes cleanup of io_context interface. Signed-off-by: Tejun Heo <tj@kernel.org> Signed-off-by: Jens Axboe <axboe@kernel.dk>
2011-12-13 23:33:42 +00:00
spin_lock(&ioc->lock);
if (likely(!radix_tree_insert(&ioc->icq_tree, q->id, icq))) {
hlist_add_head(&icq->ioc_node, &ioc->icq_list);
list_add(&icq->q_node, &q->icq_list);
if (et->ops.init_icq)
et->ops.init_icq(icq);
block, cfq: move icq creation and rq->elv.icq association to block core Now block layer knows everything necessary to create and associate icq's with requests. Move ioc_create_icq() to blk-ioc.c and update get_request() such that, if elevator_type->icq_size is set, requests are automatically associated with their matching icq's before elv_set_request(). io_context reference is also managed by block core on request alloc/free. * Only ioprio/cgroup changed handling remains from cfq_get_cic(). Collapsed into cfq_set_request(). * This removes queue kicking on icq allocation failure (for now). As icq allocation failure is rare and the only effect of queue kicking achieved was possibily accelerating queue processing, this change shouldn't be noticeable. There is a larger underlying problem. Unlike request allocation, icq allocation is not guaranteed to succeed eventually after retries. The number of icq is unbound and thus mempool can't be the solution either. This effectively adds allocation dependency on memory free path and thus possibility of deadlock. This usually wouldn't happen because icq allocation is not a hot path and, even when the condition triggers, it's highly unlikely that none of the writeback workers already has icq. However, this is still possible especially if elevator is being switched under high memory pressure, so we better get it fixed. Probably the only solution is just bypassing elevator and appending to dispatch queue on any elevator allocation failure. * Comment added to explain how icq's are managed and synchronized. This completes cleanup of io_context interface. Signed-off-by: Tejun Heo <tj@kernel.org> Signed-off-by: Jens Axboe <axboe@kernel.dk>
2011-12-13 23:33:42 +00:00
} else {
kmem_cache_free(et->icq_cache, icq);
icq = ioc_lookup_icq(q);
block, cfq: move icq creation and rq->elv.icq association to block core Now block layer knows everything necessary to create and associate icq's with requests. Move ioc_create_icq() to blk-ioc.c and update get_request() such that, if elevator_type->icq_size is set, requests are automatically associated with their matching icq's before elv_set_request(). io_context reference is also managed by block core on request alloc/free. * Only ioprio/cgroup changed handling remains from cfq_get_cic(). Collapsed into cfq_set_request(). * This removes queue kicking on icq allocation failure (for now). As icq allocation failure is rare and the only effect of queue kicking achieved was possibily accelerating queue processing, this change shouldn't be noticeable. There is a larger underlying problem. Unlike request allocation, icq allocation is not guaranteed to succeed eventually after retries. The number of icq is unbound and thus mempool can't be the solution either. This effectively adds allocation dependency on memory free path and thus possibility of deadlock. This usually wouldn't happen because icq allocation is not a hot path and, even when the condition triggers, it's highly unlikely that none of the writeback workers already has icq. However, this is still possible especially if elevator is being switched under high memory pressure, so we better get it fixed. Probably the only solution is just bypassing elevator and appending to dispatch queue on any elevator allocation failure. * Comment added to explain how icq's are managed and synchronized. This completes cleanup of io_context interface. Signed-off-by: Tejun Heo <tj@kernel.org> Signed-off-by: Jens Axboe <axboe@kernel.dk>
2011-12-13 23:33:42 +00:00
if (!icq)
printk(KERN_ERR "cfq: icq link failed!\n");
}
spin_unlock(&ioc->lock);
spin_unlock_irq(&q->queue_lock);
block, cfq: move icq creation and rq->elv.icq association to block core Now block layer knows everything necessary to create and associate icq's with requests. Move ioc_create_icq() to blk-ioc.c and update get_request() such that, if elevator_type->icq_size is set, requests are automatically associated with their matching icq's before elv_set_request(). io_context reference is also managed by block core on request alloc/free. * Only ioprio/cgroup changed handling remains from cfq_get_cic(). Collapsed into cfq_set_request(). * This removes queue kicking on icq allocation failure (for now). As icq allocation failure is rare and the only effect of queue kicking achieved was possibily accelerating queue processing, this change shouldn't be noticeable. There is a larger underlying problem. Unlike request allocation, icq allocation is not guaranteed to succeed eventually after retries. The number of icq is unbound and thus mempool can't be the solution either. This effectively adds allocation dependency on memory free path and thus possibility of deadlock. This usually wouldn't happen because icq allocation is not a hot path and, even when the condition triggers, it's highly unlikely that none of the writeback workers already has icq. However, this is still possible especially if elevator is being switched under high memory pressure, so we better get it fixed. Probably the only solution is just bypassing elevator and appending to dispatch queue on any elevator allocation failure. * Comment added to explain how icq's are managed and synchronized. This completes cleanup of io_context interface. Signed-off-by: Tejun Heo <tj@kernel.org> Signed-off-by: Jens Axboe <axboe@kernel.dk>
2011-12-13 23:33:42 +00:00
radix_tree_preload_end();
return icq;
}
struct io_cq *ioc_find_get_icq(struct request_queue *q)
{
struct io_context *ioc = current->io_context;
struct io_cq *icq = NULL;
if (unlikely(!ioc)) {
ioc = alloc_io_context(GFP_ATOMIC, q->node);
if (!ioc)
return NULL;
task_lock(current);
if (current->io_context) {
kmem_cache_free(iocontext_cachep, ioc);
ioc = current->io_context;
} else {
current->io_context = ioc;
}
get_io_context(ioc);
task_unlock(current);
} else {
get_io_context(ioc);
spin_lock_irq(&q->queue_lock);
icq = ioc_lookup_icq(q);
spin_unlock_irq(&q->queue_lock);
}
if (!icq) {
icq = ioc_create_icq(q);
if (!icq) {
put_io_context(ioc);
return NULL;
}
}
return icq;
}
EXPORT_SYMBOL_GPL(ioc_find_get_icq);
#endif /* CONFIG_BLK_ICQ */
static int __init blk_ioc_init(void)
{
iocontext_cachep = kmem_cache_create("blkdev_ioc",
sizeof(struct io_context), 0, SLAB_PANIC, NULL);
return 0;
}
subsys_initcall(blk_ioc_init);