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2014-05-30block: ensure that the timer is always addedJens Axboe1-1/+1
Commit f793aa537866 relaxed the timer addition a little too much. If the timer isn't pending, we always need to add it. Signed-off-by: Jens Axboe <axboe@fb.com>
2014-05-13blk-mq: improve support for shared tags mapsJens Axboe1-1/+12
This adds support for active queue tracking, meaning that the blk-mq tagging maintains a count of active users of a tag set. This allows us to maintain a notion of fairness between users, so that we can distribute the tag depth evenly without starving some users while allowing others to try unfair deep queues. If sharing of a tag set is detected, each hardware queue will track the depth of its own queue. And if this exceeds the total depth divided by the number of active queues, the user is actively throttled down. The active queue count is done lazily to avoid bouncing that data between submitter and completer. Each hardware queue gets marked active when it allocates its first tag, and gets marked inactive when 1) the last tag is cleared, and 2) the queue timeout grace period has passed. Signed-off-by: Jens Axboe <axboe@fb.com>
2014-04-25block: fold __blk_add_timer into blk_add_timerChristoph Hellwig1-23/+11
Signed-off-by: Christoph Hellwig <hch@lst.de> Signed-off-by: Jens Axboe <axboe@fb.com>
2014-04-24blk-mq: fix race with timeouts and requeue eventsJens Axboe1-7/+9
If a requeue event races with a timeout, we can get into the situation where we attempt to complete a request from the timeout handler when it's not start anymore. This causes a crash. So have the timeout handler check that REQ_ATOM_STARTED is still set on the request - if not, we ignore the event. If this happens, the request has now been marked as complete. As a consequence, we need to ensure to clear REQ_ATOM_COMPLETE in blk_mq_start_request(), as to maintain proper request state. Signed-off-by: Jens Axboe <axboe@fb.com>
2014-04-16block: relax when to modify the timeout timerJens Axboe1-2/+13
Since we are now, by default, applying timer slack to expiry times, the logic for when to modify a timer in the block code is suboptimal. The block layer keeps a forward rolling timer per queue for all requests, and modifies this timer if a request has a shorter timeout than what the current expiry time is. However, this breaks down when our rounded timer values get applied slack. Then each new request ends up modifying the timer, since we're still a little in front of the timer + slack. Fix this by allowing a tolerance of HZ / 2, the timeout handling doesn't need to be very precise. This drastically cuts down the number of timer modifications we have to make. Signed-off-by: Jens Axboe <axboe@fb.com>
2014-02-10blk-mq: rework I/O completionsChristoph Hellwig1-1/+1
Rework I/O completions to work more like the old code path. blk_mq_end_io now stays out of the business of deferring completions to others CPUs and calling blk_mark_rq_complete. The latter is very important to allow completing requests that have timed out and thus are already marked completed, the former allows using the IPI callout even for driver specific completions instead of having to reimplement them. Signed-off-by: Christoph Hellwig <hch@lst.de> Signed-off-by: Jens Axboe <axboe@fb.com>
2013-11-08Merge branch 'blk-mq/core' into for-3.13/coreJens Axboe1-27/+47
Signed-off-by: Jens Axboe <axboe@kernel.dk> Conflicts: block/blk-timeout.c
2013-11-08block: replace IS_ERR and PTR_ERR with PTR_ERR_OR_ZERODuan Jiong1-1/+1
This patch fixes coccinelle error regarding usage of IS_ERR and PTR_ERR instead of PTR_ERR_OR_ZERO. Signed-off-by: Duan Jiong <duanj.fnst@cn.fujitsu.com> Signed-off-by: Jens Axboe <axboe@kernel.dk>
2013-11-08block: fix race between request completion and timeout handlingJeff Moyer1-2/+1
crocode i2c_i801 i2c_core iTCO_wdt iTCO_vendor_support shpchp ioatdma dca be2net sg ses enclosure ext4 mbcache jbd2 sd_mod crc_t10dif ahci megaraid_sas(U) dm_mirror dm_region_hash dm_log dm_mod [last unloaded: scsi_wait_scan] Pid: 491, comm: scsi_eh_0 Tainted: G W ---------------- 2.6.32-220.13.1.el6.x86_64 #1 IBM -[8722PAX]-/00D1461 RIP: 0010:[<ffffffff8124e424>] [<ffffffff8124e424>] blk_requeue_request+0x94/0xa0 RSP: 0018:ffff881057eefd60 EFLAGS: 00010012 RAX: ffff881d99e3e8a8 RBX: ffff881d99e3e780 RCX: ffff881d99e3e8a8 RDX: ffff881d99e3e8a8 RSI: ffff881d99e3e780 RDI: ffff881d99e3e780 RBP: ffff881057eefd80 R08: ffff881057eefe90 R09: 0000000000000000 R10: 0000000000000000 R11: 0000000000000000 R12: ffff881057f92338 R13: 0000000000000000 R14: ffff881057f92338 R15: ffff883058188000 FS: 0000000000000000(0000) GS:ffff880040200000(0000) knlGS:0000000000000000 CS: 0010 DS: 0018 ES: 0018 CR0: 000000008005003b CR2: 00000000006d3ec0 CR3: 000000302cd7d000 CR4: 00000000000406b0 DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 DR3: 0000000000000000 DR6: 00000000ffff0ff0 DR7: 0000000000000400 Process scsi_eh_0 (pid: 491, threadinfo ffff881057eee000, task ffff881057e29540) Stack: 0000000000001057 0000000000000286 ffff8810275efdc0 ffff881057f16000 <0> ffff881057eefdd0 ffffffff81362323 ffff881057eefe20 ffffffff8135f393 <0> ffff881057e29af8 ffff8810275efdc0 ffff881057eefe78 ffff881057eefe90 Call Trace: [<ffffffff81362323>] __scsi_queue_insert+0xa3/0x150 [<ffffffff8135f393>] ? scsi_eh_ready_devs+0x5e3/0x850 [<ffffffff81362a23>] scsi_queue_insert+0x13/0x20 [<ffffffff8135e4d4>] scsi_eh_flush_done_q+0x104/0x160 [<ffffffff8135fb6b>] scsi_error_handler+0x35b/0x660 [<ffffffff8135f810>] ? scsi_error_handler+0x0/0x660 [<ffffffff810908c6>] kthread+0x96/0xa0 [<ffffffff8100c14a>] child_rip+0xa/0x20 [<ffffffff81090830>] ? kthread+0x0/0xa0 [<ffffffff8100c140>] ? child_rip+0x0/0x20 Code: 00 00 eb d1 4c 8b 2d 3c 8f 97 00 4d 85 ed 74 bf 49 8b 45 00 49 83 c5 08 48 89 de 4c 89 e7 ff d0 49 8b 45 00 48 85 c0 75 eb eb a4 <0f> 0b eb fe 0f 1f 84 00 00 00 00 00 55 48 89 e5 0f 1f 44 00 00 RIP [<ffffffff8124e424>] blk_requeue_request+0x94/0xa0 RSP <ffff881057eefd60> The RIP is this line: BUG_ON(blk_queued_rq(rq)); After digging through the code, I think there may be a race between the request completion and the timer handler running. A timer is started for each request put on the device's queue (see blk_start_request->blk_add_timer). If the request does not complete before the timer expires, the timer handler (blk_rq_timed_out_timer) will mark the request complete atomically: static inline int blk_mark_rq_complete(struct request *rq) { return test_and_set_bit(REQ_ATOM_COMPLETE, &rq->atomic_flags); } and then call blk_rq_timed_out. The latter function will call scsi_times_out, which will return one of BLK_EH_HANDLED, BLK_EH_RESET_TIMER or BLK_EH_NOT_HANDLED. If BLK_EH_RESET_TIMER is returned, blk_clear_rq_complete is called, and blk_add_timer is again called to simply wait longer for the request to complete. Now, if the request happens to complete while this is going on, what happens? Given that we know the completion handler will bail if it finds the REQ_ATOM_COMPLETE bit set, we need to focus on the completion handler running after that bit is cleared. So, from the above paragraph, after the call to blk_clear_rq_complete. If the completion sets REQ_ATOM_COMPLETE before the BUG_ON in blk_add_timer, we go boom there (I haven't seen this in the cores). Next, if we get the completion before the call to list_add_tail, then the timer will eventually fire for an old req, which may either be freed or reallocated (there is evidence that this might be the case). Finally, if the completion comes in *after* the addition to the timeout list, I think it's harmless. The request will be removed from the timeout list, req_atom_complete will be set, and all will be well. This will only actually explain the coredumps *IF* the request structure was freed, reallocated *and* queued before the error handler thread had a chance to process it. That is possible, but it may make sense to keep digging for another race. I think that if this is what was happening, we would see other instances of this problem showing up as null pointer or garbage pointer dereferences, for example when the request structure was not re-used. It looks like we actually do run into that situation in other reports. This patch moves the BUG_ON(test_bit(REQ_ATOM_COMPLETE, &req->atomic_flags)); from blk_add_timer to the only caller that could trip over it (blk_start_request). It then inverts the calls to blk_clear_rq_complete and blk_add_timer in blk_rq_timed_out to address the race. I've boot tested this patch, but nothing more. Signed-off-by: Jeff Moyer <jmoyer@redhat.com> Acked-by: Hannes Reinecke <hare@suse.de> Cc: stable@kernel.org Signed-off-by: Jens Axboe <axboe@kernel.dk>
2013-10-25blk-mq: new multi-queue block IO queueing mechanismJens Axboe1-27/+46
Linux currently has two models for block devices: - The classic request_fn based approach, where drivers use struct request units for IO. The block layer provides various helper functionalities to let drivers share code, things like tag management, timeout handling, queueing, etc. - The "stacked" approach, where a driver squeezes in between the block layer and IO submitter. Since this bypasses the IO stack, driver generally have to manage everything themselves. With drivers being written for new high IOPS devices, the classic request_fn based driver doesn't work well enough. The design dates back to when both SMP and high IOPS was rare. It has problems with scaling to bigger machines, and runs into scaling issues even on smaller machines when you have IOPS in the hundreds of thousands per device. The stacked approach is then most often selected as the model for the driver. But this means that everybody has to re-invent everything, and along with that we get all the problems again that the shared approach solved. This commit introduces blk-mq, block multi queue support. The design is centered around per-cpu queues for queueing IO, which then funnel down into x number of hardware submission queues. We might have a 1:1 mapping between the two, or it might be an N:M mapping. That all depends on what the hardware supports. blk-mq provides various helper functions, which include: - Scalable support for request tagging. Most devices need to be able to uniquely identify a request both in the driver and to the hardware. The tagging uses per-cpu caches for freed tags, to enable cache hot reuse. - Timeout handling without tracking request on a per-device basis. Basically the driver should be able to get a notification, if a request happens to fail. - Optional support for non 1:1 mappings between issue and submission queues. blk-mq can redirect IO completions to the desired location. - Support for per-request payloads. Drivers almost always need to associate a request structure with some driver private command structure. Drivers can tell blk-mq this at init time, and then any request handed to the driver will have the required size of memory associated with it. - Support for merging of IO, and plugging. The stacked model gets neither of these. Even for high IOPS devices, merging sequential IO reduces per-command overhead and thus increases bandwidth. For now, this is provided as a potential 3rd queueing model, with the hope being that, as it matures, it can replace both the classic and stacked model. That would get us back to having just 1 real model for block devices, leaving the stacked approach to dm/md devices (as it was originally intended). Contributions in this patch from the following people: Shaohua Li <shli@fusionio.com> Alexander Gordeev <agordeev@redhat.com> Christoph Hellwig <hch@infradead.org> Mike Christie <michaelc@cs.wisc.edu> Matias Bjorling <m@bjorling.me> Jeff Moyer <jmoyer@redhat.com> Acked-by: Christoph Hellwig <hch@lst.de> Signed-off-by: Jens Axboe <axboe@kernel.dk>
2013-07-01block: check for timeout function in blk_rq_timed_out()Hannes Reinecke1-2/+3
rq_timed_out_fn might have been unset while the request was in flight, so we need to check for it in blk_rq_timed_out(). Acked-by: Jens Axboe <axboe@kernel.dk> Signed-off-by: Hannes Reinecke <hare@suse.de> Signed-off-by: Stefan Weinhuber <wein@de.ibm.com> Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
2012-06-15block: Drop dead function blk_abort_queue()Asias He1-41/+0
This function was only used by btrfs code in btrfs_abort_devices() (seems in a wrong way). It was removed in commit d07eb9117050c9ed3f78296ebcc06128b52693be, So, Let's remove the dead code to avoid any confusion. Changes in v2: update commit log, btrfs_abort_devices() was removed already. Cc: Jens Axboe <axboe@kernel.dk> Cc: linux-kernel@vger.kernel.org Cc: Chris Mason <chris.mason@oracle.com> Cc: linux-btrfs@vger.kernel.org Cc: David Sterba <dave@jikos.cz> Signed-off-by: Asias He <asias@redhat.com> Signed-off-by: Jens Axboe <axboe@kernel.dk>
2011-08-03fault-injection: add ability to export fault_attr in arbitrary directoryAkinobu Mita1-1/+4
init_fault_attr_dentries() is used to export fault_attr via debugfs. But it can only export it in debugfs root directory. Per Forlin is working on mmc_fail_request which adds support to inject data errors after a completed host transfer in MMC subsystem. The fault_attr for mmc_fail_request should be defined per mmc host and export it in debugfs directory per mmc host like /sys/kernel/debug/mmc0/mmc_fail_request. init_fault_attr_dentries() doesn't help for mmc_fail_request. So this introduces fault_create_debugfs_attr() which is able to create a directory in the arbitrary directory and replace init_fault_attr_dentries(). [akpm@linux-foundation.org: extraneous semicolon, per Randy] Signed-off-by: Akinobu Mita <akinobu.mita@gmail.com> Tested-by: Per Forlin <per.forlin@linaro.org> Cc: Jens Axboe <axboe@kernel.dk> Cc: Christoph Lameter <cl@linux-foundation.org> Cc: Pekka Enberg <penberg@kernel.org> Cc: Matt Mackall <mpm@selenic.com> Cc: Randy Dunlap <rdunlap@xenotime.net> Cc: Stephen Rothwell <sfr@canb.auug.org.au> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2010-04-21block: ensure jiffies wrap is handled correctly in blk_rq_timed_out_timerRichard Kennedy1-7/+5
blk_rq_timed_out_timer() relied on blk_add_timer() never returning a timer value of zero, but commit 7838c15b8dd18e78a523513749e5b54bda07b0cb removed the code that bumped this value when it was zero. Therefore when jiffies is near wrap we could get unlucky & not set the timeout value correctly. This patch uses a flag to indicate that the timeout value was set and so handles jiffies wrap correctly, and it keeps all the logic in one function so should be easier to maintain in the future. Signed-off-by: Richard Kennedy <richard@rsk.demon.co.uk> Cc: stable@kernel.org Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
2009-04-28block: clean up misc stuff after block layer timeout conversionTejun Heo1-13/+9
* In blk_rq_timed_out_timer(), else { if } to else if * In blk_add_timer(), simplify if/else block [ Impact: cleanup ] Signed-off-by: Tejun Heo <tj@kernel.org>
2009-04-24block: fix intermittent dm timeout based oopsHannes Reinecke1-0/+7
Very rarely under stress testing of dm, oopses are occuring as something tampers with an old stack frame. This has been traced back to blk_abort_queue() leaving a timeout_list pointing to the stack. The reason is that sometimes blk_abort_request() won't delete the timer (if the request is marked as complete but before the timer has been removed, a small race window). Fix this by splicing back from the ususally empty list to the q->timeout_list. Signed-off-by: Hannes Reinecke <hare@suse.de> Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
2009-04-22block: make blk_abort_queue() ignore non-request based devicesJens Axboe1-0/+6
There's nothing to do for those devices, since the timeout handling is based on requests. Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
2009-02-18block: fix deadlock in blk_abort_queue() for drivers that readd to timeout listHannes Reinecke1-1/+8
blk_abort_queue() iterates the timeout list and aborts each request on the list, but if the driver error handling readds a request to the timeout list during this processing, we could be looping forever. Fix this by splicing current entries to a local list and run over that list instead. Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
2008-12-29block: leave the request timeout timer running even on an empty listJens Axboe1-4/+0
For sync IO, we'll often do them serialized. This means we'll be touching the queue timer for every IO, as opposed to only occasionally like we do for queued IO. Instead of deleting the timer when the last request is removed, just let continue running. If a new request comes up soon we then don't have to readd the timer again. If no new requests arrive, the timer will expire without side effect later. This improves high iops sync IO by ~1%. Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
2008-12-29block: add comment in blk_rq_timed_out() about why next can not be 0Jens Axboe1-1/+6
Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
2008-12-29block: optimizations in blk_rq_timed_out_timer()malahal@us.ibm.com1-6/+4
Now the rq->deadline can't be zero if the request is in the timeout_list, so there is no need to have next_set. There is no need to access a request's deadline field if blk_rq_timed_out is called on it. Signed-off-by: Malahal Naineni <malahal@us.ibm.com> Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
2008-11-06Block: use round_jiffies_up()Alan Stern1-17/+3
This patch (as1159b) changes the timeout routines in the block core to use round_jiffies_up(). There's no point in rounding the timer deadline down, since if it expires too early we will have to restart it. The patch also removes some unnecessary tests when a request is removed from the queue's timer list. Signed-off-by: Alan Stern <stern@rowland.harvard.edu> Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
2008-10-09block: use rq complete marking in blk_abort_request()Jens Axboe1-0/+2
We cannot abort a request if we raced with the timeout handler already, or with the IO completion. So make blk_abort_request() mark the request as complete, and only continue if we succeeded. Found and suggested by Mike Anderson <andmike@linux.vnet.ibm.com> Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
2008-10-09block: add fault injection mechanism for faking request timeoutsJens Axboe1-0/+59
Only works for the generic request timer handling. Allows one to sporadically ignore request completions, thus exercising the timeout handling. Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
2008-10-09block: Add interface to abort queued requestsMike Anderson1-0/+22
Signed-off-by: Mike Anderson <andmike@linux.vnet.ibm.com> Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
2008-10-09block: unify request timeout handlingJens Axboe1-0/+155
Right now SCSI and others do their own command timeout handling. Move those bits to the block layer. Instead of having a timer per command, we try to be a bit more clever and simply have one per-queue. This avoids the overhead of having to tear down and setup a timer for each command, so it will result in a lot less timer fiddling. Signed-off-by: Mike Anderson <andmike@linux.vnet.ibm.com> Signed-off-by: Jens Axboe <jens.axboe@oracle.com>