kernel/linux.git/drivers/md/bcache, branch v4.14.85

bcache: fix miss key refill->end in writeback

2018-11-13T19:14:45+00:00

commit 2d6cb6edd2c7fb4f40998895bda45006281b1ac5 upstream. refill->end record the last key of writeback, for example, at the first time, keys (1,128K) to (1,1024K) are flush to the backend device, but the end key (1,1024K) is not included, since the bellow code: if (bkey_cmp(k, refill->end) >= 0) { ret = MAP_DONE; goto out; } And in the next time when we refill writeback keybuf again, we searched key start from (1,1024K), and got a key bigger than it, so the key (1,1024K) missed. This patch modify the above code, and let the end key to be included to the writeback key buffer. Signed-off-by: Tang Junhui Cc: stable@vger.kernel.org Signed-off-by: Coly Li Signed-off-by: Jens Axboe Signed-off-by: Greg Kroah-Hartman

bcache: trace missed reading by cache_missed

2018-11-13T19:14:45+00:00

commit 502b291568fc7faf1ebdb2c2590f12851db0ff76 upstream. Missed reading IOs are identified by s->cache_missed, not the s->cache_miss, so in trace_bcache_read() using trace_bcache_read to identify whether the IO is missed or not. Signed-off-by: Tang Junhui Cc: stable@vger.kernel.org Signed-off-by: Coly Li Signed-off-by: Jens Axboe Signed-off-by: Greg Kroah-Hartman

bcache: release dc->writeback_lock properly in bch_writeback_thread()

2018-09-09T17:56:01+00:00

commit 3943b040f11ed0cc6d4585fd286a623ca8634547 upstream. The writeback thread would exit with a lock held when the cache device is detached via sysfs interface, fix it by releasing the held lock before exiting the while-loop. Fixes: fadd94e05c02 (bcache: quit dc->writeback_thread when BCACHE_DEV_DETACHING is set) Signed-off-by: Shan Hai Signed-off-by: Coly Li Tested-by: Shenghui Wang Cc: stable@vger.kernel.org #4.17+ Signed-off-by: Jens Axboe Signed-off-by: Greg Kroah-Hartman

bcache: quit dc->writeback_thread when BCACHE_DEV_DETACHING is set

2018-05-30T05:52:30+00:00

[ Upstream commit fadd94e05c02afec7b70b0b14915624f1782f578 ] In patch "bcache: fix cached_dev->count usage for bch_cache_set_error()", cached_dev_get() is called when creating dc->writeback_thread, and cached_dev_put() is called when exiting dc->writeback_thread. This modification works well unless people detach the bcache device manually by 'echo 1 > /sys/block/bcache/bcache/detach' Because this sysfs interface only calls bch_cached_dev_detach() which wakes up dc->writeback_thread but does not stop it. The reason is, before patch "bcache: fix cached_dev->count usage for bch_cache_set_error()", inside bch_writeback_thread(), if cache is not dirty after writeback, cached_dev_put() will be called here. And in cached_dev_make_request() when a new write request makes cache from clean to dirty, cached_dev_get() will be called there. Since we don't operate dc->count in these locations, refcount d->count cannot be dropped after cache becomes clean, and cached_dev_detach_finish() won't be called to detach bcache device. This patch fixes the issue by checking whether BCACHE_DEV_DETACHING is set inside bch_writeback_thread(). If this bit is set and cache is clean (no existing writeback_keys), break the while-loop, call cached_dev_put() and quit the writeback thread. Please note if cache is still dirty, even BCACHE_DEV_DETACHING is set the writeback thread should continue to perform writeback, this is the original design of manually detach. It is safe to do the following check without locking, let me explain why, + if (!test_bit(BCACHE_DEV_DETACHING, &dc->disk.flags) && + (!atomic_read(&dc->has_dirty) || !dc->writeback_running)) { If the kenrel thread does not sleep and continue to run due to conditions are not updated in time on the running CPU core, it just consumes more CPU cycles and has no hurt. This should-sleep-but-run is safe here. We just focus on the should-run-but-sleep condition, which means the writeback thread goes to sleep in mistake while it should continue to run. 1, First of all, no matter the writeback thread is hung or not, kthread_stop() from cached_dev_detach_finish() will wake up it and terminate by making kthread_should_stop() return true. And in normal run time, bit on index BCACHE_DEV_DETACHING is always cleared, the condition !test_bit(BCACHE_DEV_DETACHING, &dc->disk.flags) is always true and can be ignored as constant value. 2, If one of the following conditions is true, the writeback thread should go to sleep, "!atomic_read(&dc->has_dirty)" or "!dc->writeback_running)" each of them independently controls the writeback thread should sleep or not, let's analyse them one by one. 2.1 condition "!atomic_read(&dc->has_dirty)" If dc->has_dirty is set from 0 to 1 on another CPU core, bcache will call bch_writeback_queue() immediately or call bch_writeback_add() which indirectly calls bch_writeback_queue() too. In bch_writeback_queue(), wake_up_process(dc->writeback_thread) is called. It sets writeback thread's task state to TASK_RUNNING and following an implicit memory barrier, then tries to wake up the writeback thread. In writeback thread, its task state is set to TASK_INTERRUPTIBLE before doing the condition check. If other CPU core sets the TASK_RUNNING state after writeback thread setting TASK_INTERRUPTIBLE, the writeback thread will be scheduled to run very soon because its state is not TASK_INTERRUPTIBLE. If other CPU core sets the TASK_RUNNING state before writeback thread setting TASK_INTERRUPTIBLE, the implict memory barrier of wake_up_process() will make sure modification of dc->has_dirty on other CPU core is updated and observed on the CPU core of writeback thread. Therefore the condition check will correctly be false, and continue writeback code without sleeping. 2.2 condition "!dc->writeback_running)" dc->writeback_running can be changed via sysfs file, every time it is modified, a following bch_writeback_queue() is alwasy called. So the change is always observed on the CPU core of writeback thread. If dc->writeback_running is changed from 0 to 1 on other CPU core, this condition check will observe the modification and allow writeback thread to continue to run without sleeping. Now we can see, even without a locking protection, multiple conditions check is safe here, no deadlock or process hang up will happen. I compose a separte patch because that patch "bcache: fix cached_dev->count usage for bch_cache_set_error()" already gets a "Reviewed-by:" from Hannes Reinecke. Also this fix is not trivial and good for a separate patch. Signed-off-by: Coly Li Reviewed-by: Michael Lyle Cc: Hannes Reinecke Cc: Huijun Tang Signed-off-by: Jens Axboe Signed-off-by: Sasha Levin Signed-off-by: Greg Kroah-Hartman

bcache: fix kcrashes with fio in RAID5 backend dev

2018-05-30T05:52:05+00:00

[ Upstream commit 60eb34ec5526e264c2bbaea4f7512d714d791caf ] Kernel crashed when run fio in a RAID5 backend bcache device, the call trace is bellow: [ 440.012034] kernel BUG at block/blk-ioc.c:146! [ 440.012696] invalid opcode: 0000 [#1] SMP NOPTI [ 440.026537] CPU: 2 PID: 2205 Comm: md127_raid5 Not tainted 4.15.0 #8 [ 440.027441] Hardware name: HP ProLiant MicroServer Gen8, BIOS J06 07/16 /2015 [ 440.028615] RIP: 0010:put_io_context+0x8b/0x90 [ 440.029246] RSP: 0018:ffffa8c882b43af8 EFLAGS: 00010246 [ 440.029990] RAX: 0000000000000000 RBX: ffffa8c88294fca0 RCX: 0000000000 0f4240 [ 440.031006] RDX: 0000000000000004 RSI: 0000000000000286 RDI: ffffa8c882 94fca0 [ 440.032030] RBP: ffffa8c882b43b10 R08: 0000000000000003 R09: ffff949cb8 0c1700 [ 440.033206] R10: 0000000000000104 R11: 000000000000b71c R12: 00000000000 01000 [ 440.034222] R13: 0000000000000000 R14: ffff949cad84db70 R15: ffff949cb11 bd1e0 [ 440.035239] FS: 0000000000000000(0000) GS:ffff949cba280000(0000) knlGS: 0000000000000000 [ 440.060190] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 [ 440.084967] CR2: 00007ff0493ef000 CR3: 00000002f1e0a002 CR4: 00000000001 606e0 [ 440.110498] Call Trace: [ 440.135443] bio_disassociate_task+0x1b/0x60 [ 440.160355] bio_free+0x1b/0x60 [ 440.184666] bio_put+0x23/0x30 [ 440.208272] search_free+0x23/0x40 [bcache] [ 440.231448] cached_dev_write_complete+0x31/0x70 [bcache] [ 440.254468] closure_put+0xb6/0xd0 [bcache] [ 440.277087] request_endio+0x30/0x40 [bcache] [ 440.298703] bio_endio+0xa1/0x120 [ 440.319644] handle_stripe+0x418/0x2270 [raid456] [ 440.340614] ? load_balance+0x17b/0x9c0 [ 440.360506] handle_active_stripes.isra.58+0x387/0x5a0 [raid456] [ 440.380675] ? __release_stripe+0x15/0x20 [raid456] [ 440.400132] raid5d+0x3ed/0x5d0 [raid456] [ 440.419193] ? schedule+0x36/0x80 [ 440.437932] ? schedule_timeout+0x1d2/0x2f0 [ 440.456136] md_thread+0x122/0x150 [ 440.473687] ? wait_woken+0x80/0x80 [ 440.491411] kthread+0x102/0x140 [ 440.508636] ? find_pers+0x70/0x70 [ 440.524927] ? kthread_associate_blkcg+0xa0/0xa0 [ 440.541791] ret_from_fork+0x35/0x40 [ 440.558020] Code: c2 48 00 5b 41 5c 41 5d 5d c3 48 89 c6 4c 89 e7 e8 bb c2 48 00 48 8b 3d bc 36 4b 01 48 89 de e8 7c f7 e0 ff 5b 41 5c 41 5d 5d c3 <0f> 0b 0f 1f 00 0f 1f 44 00 00 55 48 8d 47 b8 48 89 e5 41 57 41 [ 440.610020] RIP: put_io_context+0x8b/0x90 RSP: ffffa8c882b43af8 [ 440.628575] ---[ end trace a1fd79d85643a73e ]-- All the crash issue happened when a bypass IO coming, in such scenario s->iop.bio is pointed to the s->orig_bio. In search_free(), it finishes the s->orig_bio by calling bio_complete(), and after that, s->iop.bio became invalid, then kernel would crash when calling bio_put(). Maybe its upper layer's faulty, since bio should not be freed before we calling bio_put(), but we'd better calling bio_put() first before calling bio_complete() to notify upper layer ending this bio. This patch moves bio_complete() under bio_put() to avoid kernel crash. [mlyle: fixed commit subject for character limits] Reported-by: Matthias Ferdinand Tested-by: Matthias Ferdinand Signed-off-by: Tang Junhui Reviewed-by: Michael Lyle Signed-off-by: Jens Axboe Signed-off-by: Sasha Levin Signed-off-by: Greg Kroah-Hartman

bcache: return attach error when no cache set exist

2018-04-26T09:02:18+00:00

[ Upstream commit 7f4fc93d4713394ee8f1cd44c238e046e11b4f15 ] I attach a back-end device to a cache set, and the cache set is not registered yet, this back-end device did not attach successfully, and no error returned: [root]# echo 87859280-fec6-4bcc-20df7ca8f86b > /sys/block/sde/bcache/attach [root]# In sysfs_attach(), the return value "v" is initialized to "size" in the beginning, and if no cache set exist in bch_cache_sets, the "v" value would not change any more, and return to sysfs, sysfs regard it as success since the "size" is a positive number. This patch fixes this issue by assigning "v" with "-ENOENT" in the initialization. Signed-off-by: Tang Junhui Reviewed-by: Michael Lyle Signed-off-by: Jens Axboe Signed-off-by: Sasha Levin Signed-off-by: Greg Kroah-Hartman

bcache: fix for data collapse after re-attaching an attached device

2018-04-26T09:02:18+00:00

[ Upstream commit 73ac105be390c1de42a2f21643c9778a5e002930 ] back-end device sdm has already attached a cache_set with ID f67ebe1f-f8bc-4d73-bfe5-9dc88607f119, then try to attach with another cache set, and it returns with an error: [root]# cd /sys/block/sdm/bcache [root]# echo 5ccd0a63-148e-48b8-afa2-aca9cbd6279f > attach -bash: echo: write error: Invalid argument After that, execute a command to modify the label of bcache device: [root]# echo data_disk1 > label Then we reboot the system, when the system power on, the back-end device can not attach to cache_set, a messages show in the log: Feb 5 12:05:52 ceph152 kernel: [922385.508498] bcache: bch_cached_dev_attach() couldn't find uuid for sdm in set In sysfs_attach(), dc->sb.set_uuid was assigned to the value which input through sysfs, no matter whether it is success or not in bch_cached_dev_attach(). For example, If the back-end device has already attached to an cache set, bch_cached_dev_attach() would fail, but dc->sb.set_uuid was changed. Then modify the label of bcache device, it will call bch_write_bdev_super(), which would write the dc->sb.set_uuid to the super block, so we record a wrong cache set ID in the super block, after the system reboot, the cache set couldn't find the uuid of the back-end device, so the bcache device couldn't exist and use any more. In this patch, we don't assigned cache set ID to dc->sb.set_uuid in sysfs_attach() directly, but input it into bch_cached_dev_attach(), and assigned dc->sb.set_uuid to the cache set ID after the back-end device attached to the cache set successful. Signed-off-by: Tang Junhui Reviewed-by: Michael Lyle Signed-off-by: Jens Axboe Signed-off-by: Sasha Levin Signed-off-by: Greg Kroah-Hartman

bcache: fix for allocator and register thread race

2018-04-26T09:02:18+00:00

[ Upstream commit 682811b3ce1a5a4e20d700939a9042f01dbc66c4 ] After long time running of random small IO writing, I reboot the machine, and after the machine power on, I found bcache got stuck, the stack is: [root@ceph153 ~]# cat /proc/2510/task/*/stack [] closure_sync+0x25/0x90 [bcache] [] bch_journal+0x118/0x2b0 [bcache] [] bch_journal_meta+0x47/0x70 [bcache] [] bch_prio_write+0x237/0x340 [bcache] [] bch_allocator_thread+0x3c8/0x3d0 [bcache] [] kthread+0xcf/0xe0 [] ret_from_fork+0x58/0x90 [] 0xffffffffffffffff [root@ceph153 ~]# cat /proc/2038/task/*/stack [] __bch_btree_map_nodes+0x12d/0x150 [bcache] [] bch_btree_insert+0xf1/0x170 [bcache] [] bch_journal_replay+0x13f/0x230 [bcache] [] run_cache_set+0x79a/0x7c2 [bcache] [] register_bcache+0xd48/0x1310 [bcache] [] kobj_attr_store+0xf/0x20 [] sysfs_write_file+0xc6/0x140 [] vfs_write+0xbd/0x1e0 [] SyS_write+0x7f/0xe0 [] system_call_fastpath+0x16/0x1 The stack shows the register thread and allocator thread were getting stuck when registering cache device. I reboot the machine several times, the issue always exsit in this machine. I debug the code, and found the call trace as bellow: register_bcache() ==>run_cache_set() ==>bch_journal_replay() ==>bch_btree_insert() ==>__bch_btree_map_nodes() ==>btree_insert_fn() ==>btree_split() //node need split ==>btree_check_reserve() In btree_check_reserve(), It will check if there is enough buckets of RESERVE_BTREE type, since allocator thread did not work yet, so no buckets of RESERVE_BTREE type allocated, so the register thread waits on c->btree_cache_wait, and goes to sleep. Then the allocator thread initialized, the call trace is bellow: bch_allocator_thread() ==>bch_prio_write() ==>bch_journal_meta() ==>bch_journal() ==>journal_wait_for_write() In journal_wait_for_write(), It will check if journal is full by journal_full(), but the long time random small IO writing causes the exhaustion of journal buckets(journal.blocks_free=0), In order to release the journal buckets, the allocator calls btree_flush_write() to flush keys to btree nodes, and waits on c->journal.wait until btree nodes writing over or there has already some journal buckets space, then the allocator thread goes to sleep. but in btree_flush_write(), since bch_journal_replay() is not finished, so no btree nodes have journal (condition "if (btree_current_write(b)->journal)" never satisfied), so we got no btree node to flush, no journal bucket released, and allocator sleep all the times. Through the above analysis, we can see that: 1) Register thread wait for allocator thread to allocate buckets of RESERVE_BTREE type; 2) Alloctor thread wait for register thread to replay journal, so it can flush btree nodes and get journal bucket. then they are all got stuck by waiting for each other. Hua Rui provided a patch for me, by allocating some buckets of RESERVE_BTREE type in advance, so the register thread can get bucket when btree node splitting and no need to waiting for the allocator thread. I tested it, it has effect, and register thread run a step forward, but finally are still got stuck, the reason is only 8 bucket of RESERVE_BTREE type were allocated, and in bch_journal_replay(), after 2 btree nodes splitting, only 4 bucket of RESERVE_BTREE type left, then btree_check_reserve() is not satisfied anymore, so it goes to sleep again, and in the same time, alloctor thread did not flush enough btree nodes to release a journal bucket, so they all got stuck again. So we need to allocate more buckets of RESERVE_BTREE type in advance, but how much is enough? By experience and test, I think it should be as much as journal buckets. Then I modify the code as this patch, and test in the machine, and it works. This patch modified base on Hua Rui’s patch, and allocate more buckets of RESERVE_BTREE type in advance to avoid register thread and allocate thread going to wait for each other. [patch v2] ca->sb.njournal_buckets would be 0 in the first time after cache creation, and no journal exists, so just 8 btree buckets is OK. Signed-off-by: Hua Rui Signed-off-by: Tang Junhui Reviewed-by: Michael Lyle Signed-off-by: Jens Axboe Signed-off-by: Sasha Levin Signed-off-by: Greg Kroah-Hartman

bcache: properly set task state in bch_writeback_thread()

2018-04-26T09:02:18+00:00

[ Upstream commit 99361bbf26337186f02561109c17a4c4b1a7536a ] Kernel thread routine bch_writeback_thread() has the following code block, 447 down_write(&dc->writeback_lock); 448~450 if (check conditions) { 451 up_write(&dc->writeback_lock); 452 set_current_state(TASK_INTERRUPTIBLE); 453 454 if (kthread_should_stop()) 455 return 0; 456 457 schedule(); 458 continue; 459 } If condition check is true, its task state is set to TASK_INTERRUPTIBLE and call schedule() to wait for others to wake up it. There are 2 issues in current code, 1, Task state is set to TASK_INTERRUPTIBLE after the condition checks, if another process changes the condition and call wake_up_process(dc-> writeback_thread), then at line 452 task state is set back to TASK_INTERRUPTIBLE, the writeback kernel thread will lose a chance to be waken up. 2, At line 454 if kthread_should_stop() is true, writeback kernel thread will return to kernel/kthread.c:kthread() with TASK_INTERRUPTIBLE and call do_exit(). It is not good to enter do_exit() with task state TASK_INTERRUPTIBLE, in following code path might_sleep() is called and a warning message is reported by __might_sleep(): "WARNING: do not call blocking ops when !TASK_RUNNING; state=1 set at [xxxx]". For the first issue, task state should be set before condition checks. Ineed because dc->writeback_lock is required when modifying all the conditions, calling set_current_state() inside code block where dc-> writeback_lock is hold is safe. But this is quite implicit, so I still move set_current_state() before all the condition checks. For the second issue, frankley speaking it does not hurt when kernel thread exits with TASK_INTERRUPTIBLE state, but this warning message scares users, makes them feel there might be something risky with bcache and hurt their data. Setting task state to TASK_RUNNING before returning fixes this problem. In alloc.c:allocator_wait(), there is also a similar issue, and is also fixed in this patch. Changelog: v3: merge two similar fixes into one patch v2: fix the race issue in v1 patch. v1: initial buggy fix. Signed-off-by: Coly Li Reviewed-by: Hannes Reinecke Reviewed-by: Michael Lyle Cc: Michael Lyle Cc: Junhui Tang Signed-off-by: Jens Axboe Signed-off-by: Sasha Levin Signed-off-by: Greg Kroah-Hartman

bcache: segregate flash only volume write streams

2018-04-12T10:32:18+00:00

[ Upstream commit 4eca1cb28d8b0574ca4f1f48e9331c5f852d43b9 ] In such scenario that there are some flash only volumes , and some cached devices, when many tasks request these devices in writeback mode, the write IOs may fall to the same bucket as bellow: | cached data | flash data | cached data | cached data| flash data| then after writeback of these cached devices, the bucket would be like bellow bucket: | free | flash data | free | free | flash data | So, there are many free space in this bucket, but since data of flash only volumes still exists, so this bucket cannot be reclaimable, which would cause waste of bucket space. In this patch, we segregate flash only volume write streams from cached devices, so data from flash only volumes and cached devices can store in different buckets. Compare to v1 patch, this patch do not add a additionally open bucket list, and it is try best to segregate flash only volume write streams from cached devices, sectors of flash only volumes may still be mixed with dirty sectors of cached device, but the number is very small. [mlyle: fixed commit log formatting, permissions, line endings] Signed-off-by: Tang Junhui Reviewed-by: Michael Lyle Signed-off-by: Michael Lyle Signed-off-by: Jens Axboe Signed-off-by: Sasha Levin Signed-off-by: Greg Kroah-Hartman