kernel/linux.git/block/blk-core.c, branch v3.4.18

block: fix request_queue->flags initialization

2012-10-21T16:27:59+00:00

commit 60ea8226cbd5c8301f9a39edc574ddabcb8150e0 upstream. A queue newly allocated with blk_alloc_queue_node() has only QUEUE_FLAG_BYPASS set. For request-based drivers, blk_init_allocated_queue() is called and q->queue_flags is overwritten with QUEUE_FLAG_DEFAULT which doesn't include BYPASS even though the initial bypass is still in effect. In blk_init_allocated_queue(), or QUEUE_FLAG_DEFAULT to q->queue_flags instead of overwriting. Signed-off-by: Tejun Heo Acked-by: Vivek Goyal Signed-off-by: Jens Axboe Signed-off-by: Greg Kroah-Hartman

block: make auto block plug flush threshold per-disk based

2012-04-06T17:37:47+00:00

We do auto block plug flush to reduce latency, the threshold is 16 requests. This works well if the task is accessing one or two drives. The problem is if the task is accessing a raid 0 device and the raid disk number is big, say 8 or 16, 16/8 = 2 or 16/16=1, we will have heavy lock contention. This patch makes the threshold per-disk based. The latency should be still ok accessing one or two drives. The setup with application accessing a lot of drives in the meantime uaually is big machine, avoiding lock contention is more important, because any contention will actually increase latency. Signed-off-by: Shaohua Li Signed-off-by: Jens Axboe

block: blk_alloc_queue_node(): use caller's GFP flags instead of GFP_KERNEL

2012-03-23T08:58:54+00:00

We should use the GFP flags that the caller specified instead of picking our own. All the callers specify GFP_KERNEL so this doesn't make a difference to how the kernel runs, it's just a cleanup. Signed-off-by: Dan Carpenter Signed-off-by: Jens Axboe

block: don't call elevator callbacks for plug merges

2012-02-08T08:19:42+00:00

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: [] 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:[] [] 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: [] elv_rq_merge_ok+0x4a/0x60 [] elv_try_merge+0x21/0x40 [] blk_queue_bio+0x8e/0x390 [] generic_make_request+0xca/0x100 [] submit_bio+0x74/0x100 [] __blockdev_direct_IO+0x1ce2/0x3450 [] blkdev_direct_IO+0x57/0x60 [] generic_file_aio_read+0x6d5/0x760 [] do_sync_read+0xe2/0x120 [] vfs_read+0xc5/0x180 [] sys_read+0x51/0x90 [] 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 LKML-Reference: <4F16F3CA.90904@kernel.dk> Original-patch-by: Jens Axboe Signed-off-by: Jens Axboe

block: separate out blk_rq_merge_ok() and blk_try_merge() from elevator functions

2012-02-08T08:19:38+00:00

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 LKML-Reference: <4F16F3CA.90904@kernel.dk> Original-patch-by: Jens Axboe Signed-off-by: Jens Axboe

block: strip out locking optimization in put_io_context()

2012-02-07T06:51:30+00:00

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 LKML-Reference: <1328514611.21268.66.camel@sli10-conroe> Signed-off-by: Jens Axboe

block: fix NULL icq_cache reference

2012-01-19T08:20:10+00:00

Vivek reported a kernel crash: [ 94.217015] BUG: unable to handle kernel NULL pointer dereference at 000000000000001c [ 94.218004] IP: [] 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:[] [] 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] [ 94.218004] [] icq_free_icq_rcu+0x16/0x20 [ 94.218004] [] __rcu_process_callbacks+0x1c2/0x420 [ 94.218004] [] rcu_process_callbacks+0x38/0x250 [ 94.218004] [] __do_softirq+0xce/0x3e0 [ 94.218004] [] ? clockevents_program_event+0x74/0x100 [ 94.218004] [] ? tick_program_event+0x24/0x30 [ 94.218004] [] call_softirq+0x1c/0x30 [ 94.218004] [] do_softirq+0x8d/0xc0 [ 94.218004] [] irq_exit+0xae/0xe0 [ 94.218004] [] smp_apic_timer_interrupt+0x6e/0x99 [ 94.218004] [] 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 Tested-by: Vivek Goyal Signed-off-by: Shaohua Li Acked-by: Tejun Heo Signed-off-by: Jens Axboe

Merge branch 'for-3.3/core' of git://git.kernel.dk/linux-block

2012-01-15T20:24:45+00:00

* '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)

block: don't kick empty queue in blk_drain_queue()

2011-12-15T19:03:04+00:00

While probing, fd sets up queue, probes hardware and tears down the queue if probing fails. In the process, blk_drain_queue() kicks the queue which failed to finish initialization and fd is unhappy about that. floppy0: no floppy controllers found ------------[ cut here ]------------ WARNING: at drivers/block/floppy.c:2929 do_fd_request+0xbf/0xd0() Hardware name: To Be Filled By O.E.M. VFS: do_fd_request called on non-open device Modules linked in: Pid: 1, comm: swapper Not tainted 3.2.0-rc4-00077-g5983fe2 #2 Call Trace: [] warn_slowpath_common+0x7a/0xb0 [] warn_slowpath_fmt+0x41/0x50 [] do_fd_request+0xbf/0xd0 [] blk_drain_queue+0x65/0x80 [] blk_cleanup_queue+0xe3/0x1a0 [] floppy_init+0xdeb/0xe28 [] ? daring+0x6b/0x6b [] do_one_initcall+0x3f/0x170 [] kernel_init+0x9d/0x11e [] ? schedule_tail+0x22/0xa0 [] kernel_thread_helper+0x4/0x10 [] ? start_kernel+0x2be/0x2be [] ? gs_change+0xb/0xb Avoid it by making blk_drain_queue() kick queue iff dispatch queue has something on it. Signed-off-by: Tejun Heo Reported-by: Ralf Hildebrandt Reported-by: Wu Fengguang Tested-by: Sergei Trofimovich Signed-off-by: Jens Axboe

block, cfq: move icq creation and rq->elv.icq association to block core

2011-12-13T23:33:42+00:00

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 Signed-off-by: Jens Axboe