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* Merge branch 'for-3.4' of ↵Linus Torvalds2012-03-201-14/+8
|\ | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | git://git.kernel.org/pub/scm/linux/kernel/git/tj/cgroup Pull cgroup changes from Tejun Heo: "Out of the 8 commits, one fixes a long-standing locking issue around tasklist walking and others are cleanups." * 'for-3.4' of git://git.kernel.org/pub/scm/linux/kernel/git/tj/cgroup: cgroup: Walk task list under tasklist_lock in cgroup_enable_task_cg_list cgroup: Remove wrong comment on cgroup_enable_task_cg_list() cgroup: remove cgroup_subsys argument from callbacks cgroup: remove extra calls to find_existing_css_set cgroup: replace tasklist_lock with rcu_read_lock cgroup: simplify double-check locking in cgroup_attach_proc cgroup: move struct cgroup_pidlist out from the header file cgroup: remove cgroup_attach_task_current_cg()
| * cgroup: remove cgroup_subsys argument from callbacksLi Zefan2012-02-021-14/+8
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | The argument is not used at all, and it's not necessary, because a specific callback handler of course knows which subsys it belongs to. Now only ->pupulate() takes this argument, because the handlers of this callback always call cgroup_add_file()/cgroup_add_files(). So we reduce a few lines of code, though the shrinking of object size is minimal. 16 files changed, 113 insertions(+), 162 deletions(-) text data bss dec hex filename 5486240 656987 7039960 13183187 c928d3 vmlinux.o.orig 5486170 656987 7039960 13183117 c9288d vmlinux.o Signed-off-by: Li Zefan <lizf@cn.fujitsu.com> Signed-off-by: Tejun Heo <tj@kernel.org>
* | Merge branch 'sched-core-for-linus' of ↵Linus Torvalds2012-03-202-24/+8
|\ \ | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip Pull scheduler changes for v3.4 from Ingo Molnar * 'sched-core-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: (27 commits) printk: Make it compile with !CONFIG_PRINTK sched/x86: Fix overflow in cyc2ns_offset sched: Fix nohz load accounting -- again! sched: Update yield() docs printk/sched: Introduce special printk_sched() for those awkward moments sched/nohz: Correctly initialize 'next_balance' in 'nohz' idle balancer sched: Cleanup cpu_active madness sched: Fix load-balance wreckage sched: Clean up parameter passing of proc_sched_autogroup_set_nice() sched: Ditch per cgroup task lists for load-balancing sched: Rename load-balancing fields sched: Move load-balancing arguments into helper struct sched/rt: Do not submit new work when PI-blocked sched/rt: Prevent idle task boosting sched/wait: Add __wake_up_all_locked() API sched/rt: Document scheduler related skip-resched-check sites sched/rt: Use schedule_preempt_disabled() sched/rt: Add schedule_preempt_disabled() sched/rt: Do not throttle when PI boosting sched/rt: Keep period timer ticking when rt throttling is active ...
| * \ Merge branch 'linus' into sched/coreIngo Molnar2012-03-019-177/+101
| |\ \ | | | | | | | | | | | | | | | | | | | | Merge reason: we'll queue up dependent patches. Signed-off-by: Ingo Molnar <mingo@elte.hu>
| * | | sched, block: Unify cache detectionPeter Zijlstra2012-01-272-24/+8
| | |/ | |/| | | | | | | | | | | | | | | | | | | | | | | | | | | | The block layer has some code trying to determine if two CPUs share a cache, the scheduler has a similar function. Expose the function used by the scheduler and make the block layer use it, thereby removing the block layers usage of CONFIG_SCHED* and topology bits. Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl> Acked-by: Jens Axboe <axboe@kernel.dk> Link: http://lkml.kernel.org/r/1327579450.2446.95.camel@twins
* | | Merge branch 'for-linus' of git://git.kernel.dk/linux-blockLinus Torvalds2012-03-144-79/+158
|\ \ \ | |_|/ |/| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | Pull block fixes from Jens Axboe: "Been sitting on this for a while, but lets get this out the door. This fixes various important bugs for 3.3 final, along with a few more trivial ones. Please pull!" * 'for-linus' of git://git.kernel.dk/linux-block: block: fix ioc leak in put_io_context block, sx8: fix pointer math issue getting fw version Block: use a freezable workqueue for disk-event polling drivers/block/DAC960: fix -Wuninitialized warning drivers/block/DAC960: fix DAC960_V2_IOCTL_Opcode_T -Wenum-compare warning block: fix __blkdev_get and add_disk race condition block: Fix setting bio flags in drivers (sd_dif/floppy) block: Fix NULL pointer dereference in sd_revalidate_disk block: exit_io_context() should call elevator_exit_icq_fn() block: simplify ioc_release_fn() block: replace icq->changed with icq->flags
| * | block: fix ioc leak in put_io_contextXiaotian Feng2012-03-141-0/+6
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | When put_io_context is called, if ioc->icq_list is empty and refcount is 1, kernel will not free the ioc. This is caught by following kmemleak: unreferenced object 0xffff880036349fe0 (size 216): comm "sh", pid 2137, jiffies 4294931140 (age 290579.412s) hex dump (first 32 bytes): 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................ 01 00 01 00 ad 4e ad de ff ff ff ff 00 00 00 00 .....N.......... backtrace: [<ffffffff8169f926>] kmemleak_alloc+0x26/0x50 [<ffffffff81195a9c>] kmem_cache_alloc_node+0x1cc/0x2a0 [<ffffffff81356b67>] create_io_context_slowpath+0x27/0x130 [<ffffffff81356d2b>] get_task_io_context+0xbb/0xf0 [<ffffffff81055f0e>] copy_process+0x188e/0x18b0 [<ffffffff8105609b>] do_fork+0x11b/0x420 [<ffffffff810247f8>] sys_clone+0x28/0x30 [<ffffffff816d3373>] stub_clone+0x13/0x20 [<ffffffffffffffff>] 0xffffffffffffffff ioc should be freed if ioc->icq_list is empty. Signed-off-by: Xiaotian Feng <dannyfeng@tencent.com> Acked-by: Vivek Goyal <vgoyal@redhat.com> Acked-by: Tejun Heo <tj@kernel.org> Signed-off-by: Jens Axboe <axboe@kernel.dk>
| * | Block: use a freezable workqueue for disk-event pollingAlan Stern2012-03-021-5/+5
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | This patch (as1519) fixes a bug in the block layer's disk-events polling. The polling is done by a work routine queued on the system_nrt_wq workqueue. Since that workqueue isn't freezable, the polling continues even in the middle of a system sleep transition. Obviously, polling a suspended drive for media changes and such isn't a good thing to do; in the case of USB mass-storage devices it can lead to real problems requiring device resets and even re-enumeration. The patch fixes things by creating a new system-wide, non-reentrant, freezable workqueue and using it for disk-events polling. Signed-off-by: Alan Stern <stern@rowland.harvard.edu> CC: <stable@kernel.org> Acked-by: Tejun Heo <tj@kernel.org> Acked-by: Rafael J. Wysocki <rjw@sisk.pl> Signed-off-by: Jens Axboe <axboe@kernel.dk>
| * | block: fix __blkdev_get and add_disk race conditionStanislaw Gruszka2012-03-021-13/+19
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | The following situation might occur: __blkdev_get: add_disk: register_disk() get_gendisk() disk_block_events() disk->ev == NULL disk_add_events() __disk_unblock_events() disk->ev != NULL --ev->block Then we unblock events, when they are suppose to be blocked. This can trigger events related block/genhd.c warnings, but also can crash in sd_check_events() or other places. I'm able to reproduce crashes with the following scripts (with connected usb dongle as sdb disk). <snip> DEV=/dev/sdb ENABLE=/sys/bus/usb/devices/1-2/bConfigurationValue function stop_me() { for i in `jobs -p` ; do kill $i 2> /dev/null ; done exit } trap stop_me SIGHUP SIGINT SIGTERM for ((i = 0; i < 10; i++)) ; do while true; do fdisk -l $DEV 2>&1 > /dev/null ; done & done while true ; do echo 1 > $ENABLE sleep 1 echo 0 > $ENABLE done </snip> I use the script to verify patch fixing oops in sd_revalidate_disk http://marc.info/?l=linux-scsi&m=132935572512352&w=2 Without Jun'ichi Nomura patch titled "Fix NULL pointer dereference in sd_revalidate_disk" or this one, script easily crash kernel within a few seconds. With both patches applied I do not observe crash. Unfortunately after some time (dozen of minutes), script will hung in: [ 1563.906432] [<c08354f5>] schedule_timeout_uninterruptible+0x15/0x20 [ 1563.906437] [<c04532d5>] msleep+0x15/0x20 [ 1563.906443] [<c05d60b2>] blk_drain_queue+0x32/0xd0 [ 1563.906447] [<c05d6e00>] blk_cleanup_queue+0xd0/0x170 [ 1563.906454] [<c06d278f>] scsi_free_queue+0x3f/0x60 [ 1563.906459] [<c06d7e6e>] __scsi_remove_device+0x6e/0xb0 [ 1563.906463] [<c06d4aff>] scsi_forget_host+0x4f/0x60 [ 1563.906468] [<c06cd84a>] scsi_remove_host+0x5a/0xf0 [ 1563.906482] [<f7f030fb>] quiesce_and_remove_host+0x5b/0xa0 [usb_storage] [ 1563.906490] [<f7f03203>] usb_stor_disconnect+0x13/0x20 [usb_storage] Anyway I think this patch is some step forward. As drawback, I do not teardown on sysfs file create error, because I do not know how to nullify disk->ev (since it can be used). However add_disk error handling practically does not exist too, and things will work without this sysfs file, except events will not be exported to user space. Signed-off-by: Stanislaw Gruszka <sgruszka@redhat.com> Acked-by: Tejun Heo <tj@kernel.org> Cc: stable@kernel.org Signed-off-by: Jens Axboe <axboe@kernel.dk>
| * | block: Fix NULL pointer dereference in sd_revalidate_diskJun'ichi Nomura2012-03-021-8/+40
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | Since 2.6.39 (1196f8b), when a driver returns -ENOMEDIUM for open(), __blkdev_get() calls rescan_partitions() to remove in-kernel partition structures and raise KOBJ_CHANGE uevent. However it ends up calling driver's revalidate_disk without open and could cause oops. In the case of SCSI: process A process B ---------------------------------------------- sys_open __blkdev_get sd_open returns -ENOMEDIUM scsi_remove_device <scsi_device torn down> rescan_partitions sd_revalidate_disk <oops> Oopses are reported here: http://marc.info/?l=linux-scsi&m=132388619710052 This patch separates the partition invalidation from rescan_partitions() and use it for -ENOMEDIUM case. Reported-by: Huajun Li <huajun.li.lee@gmail.com> Signed-off-by: Jun'ichi Nomura <j-nomura@ce.jp.nec.com> Acked-by: Tejun Heo <tj@kernel.org> Cc: stable@kernel.org Signed-off-by: Jens Axboe <axboe@kernel.dk>
| * | block: exit_io_context() should call elevator_exit_icq_fn()Tejun Heo2012-02-151-8/+47
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | 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>
| * | block: simplify ioc_release_fn()Tejun Heo2012-02-151-36/+10
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | Reverse double lock dancing in ioc_release_fn() can be simplified by just using trylock on the queue_lock and back out from ioc lock on trylock failure. Simplify it. Signed-off-by: Tejun Heo <tj@kernel.org> Tested-by: Shaohua Li <shaohua.li@intel.com> Signed-off-by: Jens Axboe <axboe@kernel.dk>
| * | block: replace icq->changed with icq->flagsTejun Heo2012-02-152-10/+32
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | icq->changed was used for ICQ_*_CHANGED bits. Rename it to flags and access it under ioc->lock instead of using atomic bitops. ioc_get_changed() is added so that the changed part can be fetched and cleared as before. icq->flags will be used to carry other flags. Signed-off-by: Tejun Heo <tj@kernel.org> Tested-by: Shaohua Li <shaohua.li@intel.com> Signed-off-by: Jens Axboe <axboe@kernel.dk>
* | | LDM: Fix reassembly of extended VBLKs.Anton Altaparmakov2012-02-241-7/+4
|/ / | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | From: Ben Hutchings <ben@decadent.org.uk> Extended VBLKs (those larger than the preset VBLK size) are divided into fragments, each with its own VBLK header. Our LDM implementation generally assumes that each VBLK is contiguous in memory, so these fragments must be assembled before further processing. Currently the reassembly seems to be done quite wrongly - no VBLK header is copied into the contiguous buffer, and the length of the header is subtracted twice from each fragment. Also the total length of the reassembled VBLK is calculated incorrectly. Signed-off-by: Ben Hutchings <ben@decadent.org.uk> Signed-off-by: Anton Altaparmakov <anton@tuxera.com>
* | block: fix lockdep warning on io_context release put_io_context()Tejun Heo2012-02-111-7/+14
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | 11a3122f6c "block: strip out locking optimization in put_io_context()" removed ioc_lock depth lockdep annoation along with locking optimization; however, while recursing from put_io_context() is no longer possible, ioc_release_fn() may still end up putting the last reference of another ioc through elevator, which wlil grab ioc->lock triggering spurious (as the ioc is always different one) A-A deadlock warning. As this can only happen one time from ioc_release_fn(), using non-zero subclass from ioc_release_fn() is enough. Use subclass 1. Signed-off-by: Tejun Heo <tj@kernel.org> Signed-off-by: Jens Axboe <axboe@kernel.dk>
* | bsg: fix sysfs link remove warningStanislaw Gruszka2012-02-081-1/+2
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | We create "bsg" link if q->kobj.sd is not NULL, so remove it only when the same condition is true. Fixes: WARNING: at fs/sysfs/inode.c:323 sysfs_hash_and_remove+0x2b/0x77() sysfs: can not remove 'bsg', no directory Call Trace: [<c0429683>] warn_slowpath_common+0x6a/0x7f [<c0537a68>] ? sysfs_hash_and_remove+0x2b/0x77 [<c042970b>] warn_slowpath_fmt+0x2b/0x2f [<c0537a68>] sysfs_hash_and_remove+0x2b/0x77 [<c053969a>] sysfs_remove_link+0x20/0x23 [<c05d88f1>] bsg_unregister_queue+0x40/0x6d [<c0692263>] __scsi_remove_device+0x31/0x9d [<c069149f>] scsi_forget_host+0x41/0x52 [<c0689fa9>] scsi_remove_host+0x71/0xe0 [<f7de5945>] quiesce_and_remove_host+0x51/0x83 [usb_storage] [<f7de5a1e>] usb_stor_disconnect+0x18/0x22 [usb_storage] [<c06c29de>] usb_unbind_interface+0x4e/0x109 [<c067a80f>] __device_release_driver+0x6b/0xa6 [<c067a861>] device_release_driver+0x17/0x22 [<c067a46a>] bus_remove_device+0xd6/0xe6 [<c06785e2>] device_del+0xf2/0x137 [<c06c101f>] usb_disable_device+0x94/0x1a0 Signed-off-by: Stanislaw Gruszka <sgruszka@redhat.com> Signed-off-by: Jens Axboe <axboe@kernel.dk>
* | block: don't call elevator callbacks for plug mergesTejun Heo2012-02-082-21/+13
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | Plug merge calls two elevator callbacks outside queue lock - elevator_allow_merge_fn() and elevator_bio_merged_fn(). Although attempt_plug_merge() suggests that elevator is guaranteed to be there through the existing request on the plug list, nothing prevents plug merge from calling into dying or initializing elevator. For regular merges, bypass ensures elvpriv count to reach zero, which in turn prevents merges as all !ELVPRIV requests get REQ_SOFTBARRIER from forced back insertion. Plug merge doesn't check ELVPRIV, and, as the requests haven't gone through elevator insertion yet, it doesn't have SOFTBARRIER set allowing merges on a bypassed queue. This, for example, leads to the following crash during elevator switch. BUG: unable to handle kernel NULL pointer dereference at 0000000000000008 IP: [<ffffffff813b34e9>] cfq_allow_merge+0x49/0xa0 PGD 112cbc067 PUD 115d5c067 PMD 0 Oops: 0000 [#1] PREEMPT SMP CPU 1 Modules linked in: deadline_iosched Pid: 819, comm: dd Not tainted 3.3.0-rc2-work+ #76 Bochs Bochs RIP: 0010:[<ffffffff813b34e9>] [<ffffffff813b34e9>] cfq_allow_merge+0x49/0xa0 RSP: 0018:ffff8801143a38f8 EFLAGS: 00010297 RAX: 0000000000000000 RBX: ffff88011817ce28 RCX: ffff880116eb6cc0 RDX: 0000000000000000 RSI: ffff880118056e20 RDI: ffff8801199512f8 RBP: ffff8801143a3908 R08: 0000000000000000 R09: 0000000000000000 R10: 0000000000000001 R11: 0000000000000000 R12: ffff880118195708 R13: ffff880118052aa0 R14: ffff8801143a3d50 R15: ffff880118195708 FS: 00007f19f82cb700(0000) GS:ffff88011fc80000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 000000008005003b CR2: 0000000000000008 CR3: 0000000112c6a000 CR4: 00000000000006e0 DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 DR3: 0000000000000000 DR6: 00000000ffff0ff0 DR7: 0000000000000400 Process dd (pid: 819, threadinfo ffff8801143a2000, task ffff880116eb6cc0) Stack: ffff88011817ce28 ffff880118195708 ffff8801143a3928 ffffffff81391bba ffff88011817ce28 ffff880118195708 ffff8801143a3948 ffffffff81391bf1 ffff88011817ce28 0000000000000000 ffff8801143a39a8 ffffffff81398e3e Call Trace: [<ffffffff81391bba>] elv_rq_merge_ok+0x4a/0x60 [<ffffffff81391bf1>] elv_try_merge+0x21/0x40 [<ffffffff81398e3e>] blk_queue_bio+0x8e/0x390 [<ffffffff81396a5a>] generic_make_request+0xca/0x100 [<ffffffff81396b04>] submit_bio+0x74/0x100 [<ffffffff811d45c2>] __blockdev_direct_IO+0x1ce2/0x3450 [<ffffffff811d0dc7>] blkdev_direct_IO+0x57/0x60 [<ffffffff811460b5>] generic_file_aio_read+0x6d5/0x760 [<ffffffff811986b2>] do_sync_read+0xe2/0x120 [<ffffffff81199345>] vfs_read+0xc5/0x180 [<ffffffff81199501>] sys_read+0x51/0x90 [<ffffffff81aeac12>] system_call_fastpath+0x16/0x1b There are multiple ways to fix this including making plug merge check ELVPRIV; however, * Calling into elevator outside queue lock is confusing and error-prone. * Requests on plug list aren't known to the elevator. They aren't on the elevator yet, so there's no elevator specific state to update. * Given the nature of plug merges - collecting bio's for the same purpose from the same issuer - elevator specific restrictions aren't applicable. So, simply don't call into elevator methods from plug merge by moving elv_bio_merged() from bio_attempt_*_merge() to blk_queue_bio(), and using blk_try_merge() in attempt_plug_merge(). This is based on Jens' patch to skip elevator_allow_merge_fn() from plug merge. Note that this makes per-cgroup merged stats skip plug merging. Signed-off-by: Tejun Heo <tj@kernel.org> LKML-Reference: <4F16F3CA.90904@kernel.dk> Original-patch-by: Jens Axboe <axboe@kernel.dk> Signed-off-by: Jens Axboe <axboe@kernel.dk>
* | block: separate out blk_rq_merge_ok() and blk_try_merge() from elevator ↵Tejun Heo2012-02-084-53/+45
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | functions blk_rq_merge_ok() is the elevator-neutral part of merge eligibility test. blk_try_merge() determines merge direction and expects the caller to have tested elv_rq_merge_ok() previously. elv_rq_merge_ok() now wraps blk_rq_merge_ok() and then calls elv_iosched_allow_merge(). elv_try_merge() is removed and the two callers are updated to call elv_rq_merge_ok() explicitly followed by blk_try_merge(). While at it, make rq_merge_ok() functions return bool. This is to prepare for plug merge update and doesn't introduce any behavior change. This is based on Jens' patch to skip elevator_allow_merge_fn() from plug merge. Signed-off-by: Tejun Heo <tj@kernel.org> LKML-Reference: <4F16F3CA.90904@kernel.dk> Original-patch-by: Jens Axboe <axboe@kernel.dk> Signed-off-by: Jens Axboe <axboe@kernel.dk>
* | block: strip out locking optimization in put_io_context()Tejun Heo2012-02-074-84/+14
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | put_io_context() performed a complex trylock dancing to avoid deferring ioc release to workqueue. It was also broken on UP because trylock was always assumed to succeed which resulted in unbalanced preemption count. While there are ways to fix the UP breakage, even the most pathological microbench (forced ioc allocation and tight fork/exit loop) fails to show any appreciable performance benefit of the optimization. Strip it out. If there turns out to be workloads which are affected by this change, simpler optimization from the discussion thread can be applied later. Signed-off-by: Tejun Heo <tj@kernel.org> LKML-Reference: <1328514611.21268.66.camel@sli10-conroe> Signed-off-by: Jens Axboe <axboe@kernel.dk>
* | block: fix ioc locking warningShaohua Li2012-02-061-1/+3
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | Meelis reported a warning: WARNING: at kernel/timer.c:1122 run_timer_softirq+0x199/0x1ec() Hardware name: 939Dual-SATA2 timer: cfq_idle_slice_timer+0x0/0xaa preempt leak: 00000102 -> 00000103 Modules linked in: sr_mod cdrom videodev media drm_kms_helper ohci_hcd ehci_hcd v4l2_compat_ioctl32 usbcore i2c_ali15x3 snd_seq drm snd_timer snd_seq Pid: 0, comm: swapper Not tainted 3.3.0-rc2-00110-gd125666 #176 Call Trace: <IRQ> [<ffffffff81022aaa>] warn_slowpath_common+0x7e/0x96 [<ffffffff8114c485>] ? cfq_slice_expired+0x1d/0x1d [<ffffffff81022b56>] warn_slowpath_fmt+0x41/0x43 [<ffffffff8114c526>] ? cfq_idle_slice_timer+0xa1/0xaa [<ffffffff8114c485>] ? cfq_slice_expired+0x1d/0x1d [<ffffffff8102c124>] run_timer_softirq+0x199/0x1ec [<ffffffff81047a53>] ? timekeeping_get_ns+0x12/0x31 [<ffffffff810145fd>] ? apic_write+0x11/0x13 [<ffffffff81027475>] __do_softirq+0x74/0xfa [<ffffffff812f337a>] call_softirq+0x1a/0x30 [<ffffffff81002ff9>] do_softirq+0x31/0x68 [<ffffffff810276cf>] irq_exit+0x3d/0xa3 [<ffffffff81014aca>] smp_apic_timer_interrupt+0x6b/0x77 [<ffffffff812f2de9>] apic_timer_interrupt+0x69/0x70 <EOI> [<ffffffff81040136>] ? sched_clock_cpu+0x73/0x7d [<ffffffff81040136>] ? sched_clock_cpu+0x73/0x7d [<ffffffff8100801f>] ? default_idle+0x1e/0x32 [<ffffffff81008019>] ? default_idle+0x18/0x32 [<ffffffff810008b1>] cpu_idle+0x87/0xd1 [<ffffffff812de861>] rest_init+0x85/0x89 [<ffffffff81659a4d>] start_kernel+0x2eb/0x2f8 [<ffffffff8165926e>] x86_64_start_reservations+0x7e/0x82 [<ffffffff81659362>] x86_64_start_kernel+0xf0/0xf7 this_q == locked_q is possible. There are two problems here: 1. In UP case, there is preemption counter issue as spin_trylock always successes. 2. In SMP case, the loop breaks too earlier. Signed-off-by: Shaohua Li <shaohua.li@intel.com> Reported-by: Meelis Roos <mroos@linux.ee> Reported-by: Knut Petersen <Knut_Petersen@t-online.de> Tested-by: Knut Petersen <Knut_Petersen@t-online.de> Signed-off-by: Jens Axboe <axboe@kernel.dk>
* | block: fix NULL icq_cache referenceShaohua Li2012-01-191-4/+6
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | Vivek reported a kernel crash: [ 94.217015] BUG: unable to handle kernel NULL pointer dereference at 000000000000001c [ 94.218004] IP: [<ffffffff81142fae>] kmem_cache_free+0x5e/0x200 [ 94.218004] PGD 13abda067 PUD 137d52067 PMD 0 [ 94.218004] Oops: 0000 [#1] SMP DEBUG_PAGEALLOC [ 94.218004] CPU 0 [ 94.218004] Modules linked in: [last unloaded: scsi_wait_scan] [ 94.218004] [ 94.218004] Pid: 0, comm: swapper/0 Not tainted 3.2.0+ #16 Hewlett-Packard HP xw6600 Workstation/0A9Ch [ 94.218004] RIP: 0010:[<ffffffff81142fae>] [<ffffffff81142fae>] kmem_cache_free+0x5e/0x200 [ 94.218004] RSP: 0018:ffff88013fc03de0 EFLAGS: 00010006 [ 94.218004] RAX: ffffffff81e0d020 RBX: ffff880138b3c680 RCX: 00000001801c001b [ 94.218004] RDX: 00000000003aac1d RSI: ffff880138b3c680 RDI: ffffffff81142fae [ 94.218004] RBP: ffff88013fc03e10 R08: ffff880137830238 R09: 0000000000000001 [ 94.218004] R10: 0000000000000000 R11: 0000000000000000 R12: 0000000000000000 [ 94.218004] R13: ffffea0004e2cf00 R14: ffffffff812f6eb6 R15: 0000000000000246 [ 94.218004] FS: 0000000000000000(0000) GS:ffff88013fc00000(0000) knlGS:0000000000000000 [ 94.218004] CS: 0010 DS: 0000 ES: 0000 CR0: 000000008005003b [ 94.218004] CR2: 000000000000001c CR3: 00000001395ab000 CR4: 00000000000006f0 [ 94.218004] DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 [ 94.218004] DR3: 0000000000000000 DR6: 00000000ffff0ff0 DR7: 0000000000000400 [ 94.218004] Process swapper/0 (pid: 0, threadinfo ffffffff81e00000, task ffffffff81e0d020) [ 94.218004] Stack: [ 94.218004] 0000000000000102 ffff88013fc0db20 ffffffff81e22700 ffff880139500f00 [ 94.218004] 0000000000000001 000000000000000a ffff88013fc03e20 ffffffff812f6eb6 [ 94.218004] ffff88013fc03e90 ffffffff810c8da2 ffffffff81e01fd8 ffff880137830240 [ 94.218004] Call Trace: [ 94.218004] <IRQ> [ 94.218004] [<ffffffff812f6eb6>] icq_free_icq_rcu+0x16/0x20 [ 94.218004] [<ffffffff810c8da2>] __rcu_process_callbacks+0x1c2/0x420 [ 94.218004] [<ffffffff810c9038>] rcu_process_callbacks+0x38/0x250 [ 94.218004] [<ffffffff810405ee>] __do_softirq+0xce/0x3e0 [ 94.218004] [<ffffffff8108ed04>] ? clockevents_program_event+0x74/0x100 [ 94.218004] [<ffffffff81090104>] ? tick_program_event+0x24/0x30 [ 94.218004] [<ffffffff8183ed1c>] call_softirq+0x1c/0x30 [ 94.218004] [<ffffffff8100422d>] do_softirq+0x8d/0xc0 [ 94.218004] [<ffffffff81040c3e>] irq_exit+0xae/0xe0 [ 94.218004] [<ffffffff8183f4be>] smp_apic_timer_interrupt+0x6e/0x99 [ 94.218004] [<ffffffff8183e330>] apic_timer_interrupt+0x70/0x80 Once a queue is quiesced, it's not supposed to have any elvpriv data or icq's, and elevator switching depends on that. Request alloc path followed the rule for elvpriv data but forgot apply it to icq's leading to the following crash during elevator switch. Fix it by not allocating icq's if ELVPRIV is not set for the request. Reported-by: Vivek Goyal <vgoyal@redhat.com> Tested-by: Vivek Goyal <vgoyal@redhat.com> Signed-off-by: Shaohua Li <shaohua.li@intel.com> Acked-by: Tejun Heo <tj@kernel.org> Signed-off-by: Jens Axboe <axboe@kernel.dk>
* | block,cfq: change code orderShaohua Li2012-01-191-3/+4
|/ | | | | | | | | | | cfq_slice_expired will change saved_workload_slice. It should be called first so saved_workload_slice is correctly set to 0 after workload type is changed. This fixes the code order changed by 54b466e44b1c7. Tested-by: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp> Signed-off-by: Shaohua Li <shaohua.li@intel.com> Signed-off-by: Jens Axboe <axboe@kernel.dk>
* cfq-iosched: fix use-after-free of cfqqJens Axboe2012-01-171-4/+3
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | With the changes in life time management between the cfq IO contexts and the cfq queues, we now risk having cfqd->active_queue being freed when cfq_slice_expired() is being called. cfq_preempt_queue() caches this queue and uses it after calling said function, causing a use-after-free condition. This triggers the following oops, when cfqq_type() attempts to dereference it: BUG: unable to handle kernel paging request at ffff8800746c4f0c IP: [<ffffffff81266d59>] cfqq_type+0xb/0x20 PGD 18d4063 PUD 1fe15067 PMD 1ffb9067 PTE 80000000746c4160 Oops: 0000 [#1] SMP DEBUG_PAGEALLOC CPU 3 Modules linked in: Pid: 1, comm: init Not tainted 3.2.0-josef+ #367 Bochs Bochs RIP: 0010:[<ffffffff81266d59>] [<ffffffff81266d59>] cfqq_type+0xb/0x20 RSP: 0018:ffff880079c11778 EFLAGS: 00010046 RAX: 0000000000000000 RBX: ffff880076f3df08 RCX: 0000000000000000 RDX: 0000000000000006 RSI: ffff880074271888 RDI: ffff8800746c4f08 RBP: ffff880079c11778 R08: 0000000000000078 R09: 0000000000000001 R10: 09f911029d74e35b R11: 09f911029d74e35b R12: ffff880076f337f0 R13: ffff8800746c4f08 R14: ffff8800746c4f08 R15: 0000000000000002 FS: 00007f62fd44f700(0000) GS:ffff88007cd80000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: ffff8800746c4f0c CR3: 0000000076c21000 CR4: 00000000000006e0 DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 DR3: 0000000000000000 DR6: 00000000ffff0ff0 DR7: 0000000000000400 Process init (pid: 1, threadinfo ffff880079c10000, task ffff880079c0a040) Stack: ffff880079c117c8 ffffffff812683d8 ffff880079c117a8 ffffffff8125de43 ffff8800744fcf48 ffff880074b43e98 ffff8800770c8828 ffff880074b43e98 0000000000000003 0000000000000000 ffff880079c117f8 ffffffff81254149 Call Trace: [<ffffffff812683d8>] cfq_insert_request+0x3f5/0x47c [<ffffffff8125de43>] ? blk_recount_segments+0x20/0x31 [<ffffffff81254149>] __elv_add_request+0x1ca/0x200 [<ffffffff8125aa99>] blk_queue_bio+0x2ef/0x312 [<ffffffff81258f7b>] generic_make_request+0x9f/0xe0 [<ffffffff8125907b>] submit_bio+0xbf/0xca [<ffffffff81136ec7>] submit_bh+0xdf/0xfe [<ffffffff81176d04>] ext3_bread+0x50/0x99 [<ffffffff811785b3>] dx_probe+0x38/0x291 [<ffffffff81178864>] ext3_dx_find_entry+0x58/0x219 [<ffffffff81178ad5>] ext3_find_entry+0xb0/0x406 [<ffffffff8110c4d5>] ? cache_alloc_debugcheck_after.isra.46+0x14d/0x1a0 [<ffffffff8110cfbd>] ? kmem_cache_alloc+0xef/0x191 [<ffffffff8117a330>] ext3_lookup+0x39/0xe1 [<ffffffff81119461>] d_alloc_and_lookup+0x45/0x6c [<ffffffff8111ac41>] do_lookup+0x1e4/0x2f5 [<ffffffff8111aef6>] link_path_walk+0x1a4/0x6ef [<ffffffff8111b557>] path_lookupat+0x59/0x5ea [<ffffffff8127406c>] ? __strncpy_from_user+0x30/0x5a [<ffffffff8111bce0>] do_path_lookup+0x23/0x59 [<ffffffff8111cfd6>] user_path_at_empty+0x53/0x99 [<ffffffff8107b37b>] ? remove_wait_queue+0x51/0x56 [<ffffffff8111d02d>] user_path_at+0x11/0x13 [<ffffffff811141f5>] vfs_fstatat+0x3a/0x64 [<ffffffff8111425a>] vfs_stat+0x1b/0x1d [<ffffffff81114359>] sys_newstat+0x1a/0x33 [<ffffffff81060e12>] ? task_stopped_code+0x42/0x42 [<ffffffff815d6712>] system_call_fastpath+0x16/0x1b Code: 89 e6 48 89 c7 e8 fa ca fe ff 85 c0 74 06 4c 89 2b 41 b6 01 5b 44 89 f0 41 5c 41 5d 41 5e 5d c3 55 48 89 e5 66 66 66 66 90 31 c0 <8b> 57 04 f6 c6 01 74 0b 83 e2 20 83 fa 01 19 c0 83 c0 02 5d c3 RIP [<ffffffff81266d59>] cfqq_type+0xb/0x20 RSP <ffff880079c11778> CR2: ffff8800746c4f0c Get rid of the caching of cfqd->active_queue, and reorder the check so that it happens before we expire the active queue. Thanks to Tejun for pin pointing the error location. Reported-by: Chris Mason <chris.mason@oracle.com> Tested-by: Chris Mason <chris.mason@oracle.com> Signed-off-by: Jens Axboe <axboe@kernel.dk>
* Merge branch 'for-3.3/core' of git://git.kernel.dk/linux-blockLinus Torvalds2012-01-1516-821/+847
|\ | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | * 'for-3.3/core' of git://git.kernel.dk/linux-block: (37 commits) Revert "block: recursive merge requests" block: Stop using macro stubs for the bio data integrity calls blockdev: convert some macros to static inlines fs: remove unneeded plug in mpage_readpages() block: Add BLKROTATIONAL ioctl block: Introduce blk_set_stacking_limits function block: remove WARN_ON_ONCE() in exit_io_context() block: an exiting task should be allowed to create io_context block: ioc_cgroup_changed() needs to be exported block: recursive merge requests block, cfq: fix empty queue crash caused by request merge block, cfq: move icq creation and rq->elv.icq association to block core block, cfq: restructure io_cq creation path for io_context interface cleanup block, cfq: move io_cq exit/release to blk-ioc.c block, cfq: move icq cache management to block core block, cfq: move io_cq lookup to blk-ioc.c block, cfq: move cfqd->icq_list to request_queue and add request->elv.icq block, cfq: reorganize cfq_io_context into generic and cfq specific parts block: remove elevator_queue->ops block: reorder elevator switch sequence ... Fix up conflicts in: - block/blk-cgroup.c Switch from can_attach_task to can_attach - block/cfq-iosched.c conflict with now removed cic index changes (we now use q->id instead)
| * Revert "block: recursive merge requests"Jens Axboe2012-01-151-12/+4
| | | | | | | | | | | | | | | | | | | | | | | | This reverts commit 274193224cdabd687d804a26e0150bb20f2dd52c. We have some problems related to selection of empty queues that need to be resolved, evidence so far points to the recursive merge logic making either being the cause or at least the accelerator for this. So revert it for now, until we figure this out. Signed-off-by: Jens Axboe <axboe@kernel.dk>
| * block: Add BLKROTATIONAL ioctlMartin K. Petersen2012-01-112-0/+5
| | | | | | | | | | | | | | | | Introduce an ioctl which permits applications to query whether a block device is rotational. Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com> Signed-off-by: Jens Axboe <axboe@kernel.dk>
| * block: Introduce blk_set_stacking_limits functionMartin K. Petersen2012-01-111-8/+24
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | Stacking driver queue limits are typically bounded exclusively by the capabilities of the low level devices, not by the stacking driver itself. This patch introduces blk_set_stacking_limits() which has more liberal metrics than the default queue limits function. This allows us to inherit topology parameters from bottom devices without manually tweaking the default limits in each driver prior to calling the stacking function. Since there is now a clear distinction between stacking and low-level devices, blk_set_default_limits() has been modified to carry the more conservative values that we used to manually set in blk_queue_make_request(). Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com> Acked-by: Mike Snitzer <snitzer@redhat.com> Signed-off-by: Jens Axboe <axboe@kernel.dk>
| * block: remove WARN_ON_ONCE() in exit_io_context()Tejun Heo2011-12-271-3/+0
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | 6e736be7 "block: make ioc get/put interface more conventional and fix race on alloction" added WARN_ON_ONCE() in exit_io_context() which triggers if !PF_EXITING. All tasks hitting exit_io_context() from task exit should have PF_EXITING set but task struct tearing down after fork failure calls into the function without PF_EXITING, triggering the condition. WARNING: at block/blk-ioc.c:234 exit_io_context+0x40/0x92() Pid: 17090, comm: trinity Not tainted 3.2.0-rc6-next-20111222-sasha-dirty #77 Call Trace: [<ffffffff810b69a3>] warn_slowpath_common+0x8f/0xb2 [<ffffffff810b6a77>] warn_slowpath_null+0x18/0x1a [<ffffffff8181a7a2>] exit_io_context+0x40/0x92 [<ffffffff810b58c9>] copy_process+0x126f/0x1453 [<ffffffff810b5c1b>] do_fork+0x120/0x3e9 [<ffffffff8106242f>] sys_clone+0x26/0x28 [<ffffffff82425803>] stub_clone+0x13/0x20 ---[ end trace a2e4eb670b375238 ]--- Reported-by: Sasha Levin <levinsasha928@gmail.com> Signed-off-by: Tejun Heo <tj@kernel.org> Signed-off-by: Jens Axboe <axboe@kernel.dk>
| * block: an exiting task should be allowed to create io_contextTejun Heo2011-12-251-2/+9
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | While fixing io_context creation / task exit race condition, 6e736be7f2 "block: make ioc get/put interface more conventional and fix race on alloction" also prevented an exiting (%PF_EXITING) task from creating its own io_context. This is incorrect as exit path may issue IOs, e.g. from exit_files(), and if those IOs are the first ones issued by the task, io_context needs to be created to process the IOs. Combined with the existing problem of io_context / io_cq creation failure having the possibility of stalling IO, this problem results in deterministic full IO lockup with certain workloads. Fix it by allowing io_context creation regardless of %PF_EXITING for %current. Signed-off-by: Tejun Heo <tj@kernel.org> Reported-by: Andrew Morton <akpm@linux-foundation.org> Reported-by: Hugh Dickins <hughd@google.com> Signed-off-by: Jens Axboe <axboe@kernel.dk>
| * block: ioc_cgroup_changed() needs to be exportedJens Axboe2011-12-191-0/+1
| | | | | | | | | | | | | | | | With the ioc changed, ioc_cgroup_changed() can be used by modular code. So ensure that it is exported. Reported-by: Stephen Rothwell <sfr@canb.auug.org.au> Signed-off-by: Jens Axboe <axboe@kernel.dk>
| * block: recursive merge requestsShaohua Li2011-12-161-4/+12
| | | | | | | | | | | | | | | | | | | | | | | | In my workload, thread 1 accesses a, a+2, ..., thread 2 accesses a+1, a+3,.... When the requests are flushed to queue, a and a+1 are merged to (a, a+1), a+2 and a+3 too to (a+2, a+3), but (a, a+1) and (a+2, a+3) aren't merged. With recursive merge below, the workload throughput gets improved 20% and context switch drops 60%. Signed-off-by: Shaohua Li <shaohua.li@intel.com> Signed-off-by: Jens Axboe <axboe@kernel.dk>
| * block, cfq: fix empty queue crash caused by request mergeShaohua Li2011-12-161-0/+12
| | | | | | | | | | | | | | | | | | | | | | All requests of a queue could be merged to other requests of other queue. Such queue will not have request in it, but it's in service tree. This will cause kernel oops. I encounter a BUG_ON() in cfq_dispatch_request() with next patch, but the issue should exist without the patch. Signed-off-by: Shaohua Li <shaohua.li@intel.com> Signed-off-by: Jens Axboe <axboe@kernel.dk>
| * block, cfq: move icq creation and rq->elv.icq association to block coreTejun Heo2011-12-144-132/+110
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | 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>
| * block, cfq: restructure io_cq creation path for io_context interface cleanupTejun Heo2011-12-141-53/+41
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | Add elevator_ops->elevator_init_icq_fn() and restructure cfq_create_cic() and rename it to ioc_create_icq(). The new function expects its caller to pass in io_context, uses elevator_type->icq_cache, handles generic init, calls the new elevator operation for elevator specific initialization, and returns pointer to created or looked up icq. This leaves cfq_icq_pool variable without any user. Removed. This prepares for io_context interface cleanup and doesn't introduce any functional difference. Signed-off-by: Tejun Heo <tj@kernel.org> Signed-off-by: Jens Axboe <axboe@kernel.dk>
| * block, cfq: move io_cq exit/release to blk-ioc.cTejun Heo2011-12-145-55/+78
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | With kmem_cache managed by blk-ioc, io_cq exit/release can be moved to blk-ioc too. The odd ->io_cq->exit/release() callbacks are replaced with elevator_ops->elevator_exit_icq_fn() with unlinking from both ioc and q, and freeing automatically handled by blk-ioc. The elevator operation only need to perform exit operation specific to the elevator - in cfq's case, exiting the cfqq's. Also, clearing of io_cq's on q detach is moved to block core and automatically performed on elevator switch and q release. Because the q io_cq points to might be freed before RCU callback for the io_cq runs, blk-ioc code should remember to which cache the io_cq needs to be freed when the io_cq is released. New field io_cq->__rcu_icq_cache is added for this purpose. As both the new field and rcu_head are used only after io_cq is released and the q/ioc_node fields aren't, they are put into unions. Signed-off-by: Tejun Heo <tj@kernel.org> Signed-off-by: Jens Axboe <axboe@kernel.dk>
| * block, cfq: move icq cache management to block coreTejun Heo2011-12-144-41/+52
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | Let elevators set ->icq_size and ->icq_align in elevator_type and elv_register() and elv_unregister() respectively create and destroy kmem_cache for icq. * elv_register() now can return failure. All callers updated. * icq caches are automatically named "ELVNAME_io_cq". * cfq_slab_setup/kill() are collapsed into cfq_init/exit(). * While at it, minor indentation change for iosched_cfq.elevator_name for consistency. This will help moving icq management to block core. This doesn't introduce any functional change. Signed-off-by: Tejun Heo <tj@kernel.org> Signed-off-by: Jens Axboe <axboe@kernel.dk>
| * block, cfq: move io_cq lookup to blk-ioc.cTejun Heo2011-12-143-40/+45
| | | | | | | | | | | | | | | | | | | | | | | | | | Now that all io_cq related data structures are in block core layer, io_cq lookup can be moved from cfq-iosched.c to blk-ioc.c. Lookup logic from cfq_cic_lookup() is moved to ioc_lookup_icq() with parameter return type changes (cfqd -> request_queue, cfq_io_cq -> io_cq) and cfq_cic_lookup() becomes thin wrapper around cfq_cic_lookup(). Signed-off-by: Tejun Heo <tj@kernel.org> Signed-off-by: Jens Axboe <axboe@kernel.dk>
| * block, cfq: move cfqd->icq_list to request_queue and add request->elv.icqTejun Heo2011-12-143-19/+12
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | Most of icq management is about to be moved out of cfq into blk-ioc. This patch prepares for it. * Move cfqd->icq_list to request_queue->icq_list * Make request explicitly point to icq instead of through elevator private data. ->elevator_private[3] is replaced with sub struct elv which contains icq pointer and priv[2]. cfq is updated accordingly. * Meaningless clearing of ->elevator_private[0] removed from elv_set_request(). At that point in code, the field was guaranteed to be %NULL anyway. This patch doesn't introduce any functional change. Signed-off-by: Tejun Heo <tj@kernel.org> Signed-off-by: Jens Axboe <axboe@kernel.dk>
| * block, cfq: reorganize cfq_io_context into generic and cfq specific partsTejun Heo2011-12-142-145/+161
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | Currently io_context and cfq logics are mixed without clear boundary. Most of io_context is independent from cfq but cfq_io_context handling logic is dispersed between generic ioc code and cfq. cfq_io_context represents association between an io_context and a request_queue, which is a concept useful outside of cfq, but it also contains fields which are useful only to cfq. This patch takes out generic part and put it into io_cq (io context-queue) and the rest into cfq_io_cq (cic moniker remains the same) which contains io_cq. The following changes are made together. * cfq_ttime and cfq_io_cq now live in cfq-iosched.c. * All related fields, functions and constants are renamed accordingly. * ioc->ioc_data is now "struct io_cq *" instead of "void *" and renamed to icq_hint. This prepares for io_context API cleanup. Documentation is currently sparse. It will be added later. Changes in this patch are mechanical and don't cause functional change. Signed-off-by: Tejun Heo <tj@kernel.org> Signed-off-by: Jens Axboe <axboe@kernel.dk>
| * block: remove elevator_queue->opsTejun Heo2011-12-142-43/+41
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | elevator_queue->ops points to the same ops struct ->elevator_type.ops is pointing to. The only effect of caching it in elevator_queue is shorter notation - it doesn't save any indirect derefence. Relocate elevator_type->list which used only during module init/exit to the end of the structure, rename elevator_queue->elevator_type to ->type, and replace elevator_queue->ops with elevator_queue->type.ops. This doesn't introduce any functional difference. Signed-off-by: Tejun Heo <tj@kernel.org> Signed-off-by: Jens Axboe <axboe@kernel.dk>
| * block: reorder elevator switch sequenceTejun Heo2011-12-141-54/+37
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | Elevator switch sequence first attached the new elevator, then tried registering it (sysfs) and if that failed attached back the old elevator. However, sysfs registration doesn't require the elevator to be attached, so there is no reason to do the "detach, attach new, register, maybe re-attach old" sequence. It can just do "register, detach, attach". * elevator_init_queue() is updated to set ->elevator_data directly and return 0 / -errno. This allows elevator_exit() on an unattached elevator. * __elv_unregister_queue() which was necessary to unregister unattached q is removed in favor of __elv_register_queue() which can register unattached q. * elevator_attach() becomes a single assignment and obscures more then it helps. Dropped. This will help cleaning up io_context handling across elevator switch. This patch doesn't introduce visible behavior change. Signed-off-by: Tejun Heo <tj@kernel.org> Signed-off-by: Jens Axboe <axboe@kernel.dk>
| * block, cfq: replace current_io_context() with create_io_context()Tejun Heo2011-12-144-54/+71
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | When called under queue_lock, current_io_context() triggers lockdep warning if it hits allocation path. This is because io_context installation is protected by task_lock which is not IRQ safe, so it triggers irq-unsafe-lock -> irq -> irq-safe-lock -> irq-unsafe-lock deadlock warning. Given the restriction, accessor + creator rolled into one doesn't work too well. Drop current_io_context() and let the users access task->io_context directly inside queue_lock combined with explicit creation using create_io_context(). Future ioc updates will further consolidate ioc access and the create interface will be unexported. While at it, relocate ioc internal interface declarations in blk.h and add section comments before and after. This patch does not introduce functional change. Signed-off-by: Tejun Heo <tj@kernel.org> Signed-off-by: Jens Axboe <axboe@kernel.dk>
| * block, cfq: kill cic->keyTejun Heo2011-12-141-21/+5
| | | | | | | | | | | | | | | | Now that lazy paths are removed, cfqd_dead_key() is meaningless and cic->q can be used whereever cic->key is used. Kill cic->key. Signed-off-by: Tejun Heo <tj@kernel.org> Signed-off-by: Jens Axboe <axboe@kernel.dk>
| * block, cfq: kill ioc_goneTejun Heo2011-12-141-38/+5
| | | | | | | | | | | | | | | | | | | | | | Now that cic's are immediately unlinked under both locks, there's no need to count and drain cic's before module unload. RCU callback completion is waited with rcu_barrier(). While at it, remove residual RCU operations on cic_list. Signed-off-by: Tejun Heo <tj@kernel.org> Signed-off-by: Jens Axboe <axboe@kernel.dk>
| * block, cfq: remove delayed unlinkTejun Heo2011-12-142-98/+10
| | | | | | | | | | | | | | | | | | | | | | Now that all cic's are immediately unlinked from both ioc and queue, lazy dropping from lookup path and trimming on elevator unregister are unnecessary. Kill them and remove now unused elevator_ops->trim(). This also leaves call_for_each_cic() without any user. Removed. Signed-off-by: Tejun Heo <tj@kernel.org> Signed-off-by: Jens Axboe <axboe@kernel.dk>
| * block, cfq: unlink cfq_io_context's immediatelyTejun Heo2011-12-143-66/+146
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | 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>
| * block, cfq: fix cic lookup lockingTejun Heo2011-12-141-32/+35
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | * cfq_cic_lookup() may be called without queue_lock and multiple tasks can execute it simultaneously for the same shared ioc. Nothing prevents them racing each other and trying to drop the same dead cic entry multiple times. * smp_wmb() in cfq_exit_cic() doesn't really do anything and nothing prevents cfq_cic_lookup() seeing stale cic->key. This usually doesn't blow up because by the time cic is exited, all requests have been drained and new requests are terminated before going through elevator. However, it can still be triggered by plug merge path which doesn't grab queue_lock and thus can't check DEAD state reliably. This patch updates lookup locking such that, * Lookup is always performed under queue_lock. This doesn't add any more locking. The only issue is cfq_allow_merge() which can be called from plug merge path without holding any lock. For now, this is worked around by using cic of the request to merge into, which is guaranteed to have the same ioc. For longer term, I think it would be best to separate out plug merge method from regular one. * Spurious ioc->lock locking around cic lookup hint assignment dropped. Signed-off-by: Tejun Heo <tj@kernel.org> Signed-off-by: Jens Axboe <axboe@kernel.dk>
| * block, cfq: fix race condition in cic creation path and tighten lockingTejun Heo2011-12-141-59/+76
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | cfq_get_io_context() would fail if multiple tasks race to insert cic's for the same association. This patch restructures cfq_get_io_context() such that slow path insertion race is handled properly. Note that the restructuring also makes cfq_get_io_context() called under queue_lock and performs both ioc and cfqd insertions while holding both ioc and queue locks. This is part of on-going locking tightening and will be used to simplify synchronization rules. Signed-off-by: Tejun Heo <tj@kernel.org> Signed-off-by: Jens Axboe <axboe@kernel.dk>
| * block, cfq: move ioc ioprio/cgroup changed handling to cicTejun Heo2011-12-143-20/+55
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | ioprio/cgroup change was handled by marking the changed state in ioc and, on the following access to the ioc, performing RCU-protected iteration through all cic's grabbing the matching queue_lock. This patch moves the changed state to each cic. When ioprio or cgroup changes, the respective bit is set on all cic's of the ioc and when each of those cic (not ioc) is accessed, change is applied for that specific ioc-queue pair. This also fixes the following two race conditions between setting and clearing of changed states. * Missing barrier between assign/load of ioprio and ioprio_changed allowed applying old ioprio. * Change requests could happen between application of change and clearing of changed variables. Signed-off-by: Tejun Heo <tj@kernel.org> Signed-off-by: Jens Axboe <axboe@kernel.dk>
| * block, cfq: misc updates to cfq_io_contextTejun Heo2011-12-141-26/+32
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | Make the following changes to prepare for ioc/cic management cleanup. * Add cic->q so that ioc can determine the associated queue without querying cfq. This will eventually replace ->key. * Factor out cfq_release_cic() from cic_free_func(). This function assumes that the caller handled locking. * Rename __cfq_exit_single_io_context() to cfq_exit_cic() and make it take only @cic. * Restructure cfq_cic_link() for future updates. This patch doesn't introduce any functional changes. Signed-off-by: Tejun Heo <tj@kernel.org> Signed-off-by: Jens Axboe <axboe@kernel.dk>
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