kernel/drivers/md/bcache/super.c, branch linux-5.1.y

Revert "bcache: set CACHE_SET_IO_DISABLE in bch_cached_dev_error()"

2019-07-26T07:12:54Z

commit 695277f16b3a102fcc22c97fdf2de77c7b19f0b3 upstream. This reverts commit 6147305c73e4511ca1a975b766b97a779d442567. Although this patch helps the failed bcache device to stop faster when too many I/O errors detected on corresponding cached device, setting CACHE_SET_IO_DISABLE bit to cache set c->flags was not a good idea. This operation will disable all I/Os on cache set, which means other attached bcache devices won't work neither. Without this patch, the failed bcache device can also be stopped eventually if internal I/O accomplished (e.g. writeback). Therefore here I revert it. Fixes: 6147305c73e4 ("bcache: set CACHE_SET_IO_DISABLE in bch_cached_dev_error()") Reported-by: Yong Li Signed-off-by: Coly Li Cc: stable@vger.kernel.org Signed-off-by: Jens Axboe Signed-off-by: Greg Kroah-Hartman

bcache: fix potential deadlock in cached_def_free()

2019-07-26T07:12:46Z

[ Upstream commit 7e865eba00a3df2dc8c4746173a8ca1c1c7f042e ] When enable lockdep and reboot system with a writeback mode bcache device, the following potential deadlock warning is reported by lockdep engine. [ 101.536569][ T401] kworker/2:2/401 is trying to acquire lock: [ 101.538575][ T401] 00000000bbf6e6c7 ((wq_completion)bcache_writeback_wq){+.+.}, at: flush_workqueue+0x87/0x4c0 [ 101.542054][ T401] [ 101.542054][ T401] but task is already holding lock: [ 101.544587][ T401] 00000000f5f305b3 ((work_completion)(&cl->work)#2){+.+.}, at: process_one_work+0x21e/0x640 [ 101.548386][ T401] [ 101.548386][ T401] which lock already depends on the new lock. [ 101.548386][ T401] [ 101.551874][ T401] [ 101.551874][ T401] the existing dependency chain (in reverse order) is: [ 101.555000][ T401] [ 101.555000][ T401] -> #1 ((work_completion)(&cl->work)#2){+.+.}: [ 101.557860][ T401] process_one_work+0x277/0x640 [ 101.559661][ T401] worker_thread+0x39/0x3f0 [ 101.561340][ T401] kthread+0x125/0x140 [ 101.562963][ T401] ret_from_fork+0x3a/0x50 [ 101.564718][ T401] [ 101.564718][ T401] -> #0 ((wq_completion)bcache_writeback_wq){+.+.}: [ 101.567701][ T401] lock_acquire+0xb4/0x1c0 [ 101.569651][ T401] flush_workqueue+0xae/0x4c0 [ 101.571494][ T401] drain_workqueue+0xa9/0x180 [ 101.573234][ T401] destroy_workqueue+0x17/0x250 [ 101.575109][ T401] cached_dev_free+0x44/0x120 [bcache] [ 101.577304][ T401] process_one_work+0x2a4/0x640 [ 101.579357][ T401] worker_thread+0x39/0x3f0 [ 101.581055][ T401] kthread+0x125/0x140 [ 101.582709][ T401] ret_from_fork+0x3a/0x50 [ 101.584592][ T401] [ 101.584592][ T401] other info that might help us debug this: [ 101.584592][ T401] [ 101.588355][ T401] Possible unsafe locking scenario: [ 101.588355][ T401] [ 101.590974][ T401] CPU0 CPU1 [ 101.592889][ T401] ---- ---- [ 101.594743][ T401] lock((work_completion)(&cl->work)#2); [ 101.596785][ T401] lock((wq_completion)bcache_writeback_wq); [ 101.600072][ T401] lock((work_completion)(&cl->work)#2); [ 101.602971][ T401] lock((wq_completion)bcache_writeback_wq); [ 101.605255][ T401] [ 101.605255][ T401] *** DEADLOCK *** [ 101.605255][ T401] [ 101.608310][ T401] 2 locks held by kworker/2:2/401: [ 101.610208][ T401] #0: 00000000cf2c7d17 ((wq_completion)events){+.+.}, at: process_one_work+0x21e/0x640 [ 101.613709][ T401] #1: 00000000f5f305b3 ((work_completion)(&cl->work)#2){+.+.}, at: process_one_work+0x21e/0x640 [ 101.617480][ T401] [ 101.617480][ T401] stack backtrace: [ 101.619539][ T401] CPU: 2 PID: 401 Comm: kworker/2:2 Tainted: G W 5.2.0-rc4-lp151.20-default+ #1 [ 101.623225][ T401] Hardware name: VMware, Inc. VMware Virtual Platform/440BX Desktop Reference Platform, BIOS 6.00 04/13/2018 [ 101.627210][ T401] Workqueue: events cached_dev_free [bcache] [ 101.629239][ T401] Call Trace: [ 101.630360][ T401] dump_stack+0x85/0xcb [ 101.631777][ T401] print_circular_bug+0x19a/0x1f0 [ 101.633485][ T401] __lock_acquire+0x16cd/0x1850 [ 101.635184][ T401] ? __lock_acquire+0x6a8/0x1850 [ 101.636863][ T401] ? lock_acquire+0xb4/0x1c0 [ 101.638421][ T401] ? find_held_lock+0x34/0xa0 [ 101.640015][ T401] lock_acquire+0xb4/0x1c0 [ 101.641513][ T401] ? flush_workqueue+0x87/0x4c0 [ 101.643248][ T401] flush_workqueue+0xae/0x4c0 [ 101.644832][ T401] ? flush_workqueue+0x87/0x4c0 [ 101.646476][ T401] ? drain_workqueue+0xa9/0x180 [ 101.648303][ T401] drain_workqueue+0xa9/0x180 [ 101.649867][ T401] destroy_workqueue+0x17/0x250 [ 101.651503][ T401] cached_dev_free+0x44/0x120 [bcache] [ 101.653328][ T401] process_one_work+0x2a4/0x640 [ 101.655029][ T401] worker_thread+0x39/0x3f0 [ 101.656693][ T401] ? process_one_work+0x640/0x640 [ 101.658501][ T401] kthread+0x125/0x140 [ 101.660012][ T401] ? kthread_create_worker_on_cpu+0x70/0x70 [ 101.661985][ T401] ret_from_fork+0x3a/0x50 [ 101.691318][ T401] bcache: bcache_device_free() bcache0 stopped Here is how the above potential deadlock may happen in reboot/shutdown code path, 1) bcache_reboot() is called firstly in the reboot/shutdown code path, then in bcache_reboot(), bcache_device_stop() is called. 2) bcache_device_stop() sets BCACHE_DEV_CLOSING on d->falgs, then call closure_queue(&d->cl) to invoke cached_dev_flush(). And in turn cached_dev_flush() calls cached_dev_free() via closure_at() 3) In cached_dev_free(), after stopped writebach kthread dc->writeback_thread, the kwork dc->writeback_write_wq is stopping by destroy_workqueue(). 4) Inside destroy_workqueue(), drain_workqueue() is called. Inside drain_workqueue(), flush_workqueue() is called. Then wq->lockdep_map is acquired by lock_map_acquire() in flush_workqueue(). After the lock acquired the rest part of flush_workqueue() just wait for the workqueue to complete. 5) Now we look back at writeback thread routine bch_writeback_thread(), in the main while-loop, write_dirty() is called via continue_at() in read_dirty_submit(), which is called via continue_at() in while-loop level called function read_dirty(). Inside write_dirty() it may be re-called on workqueeu dc->writeback_write_wq via continue_at(). It means when the writeback kthread is stopped in cached_dev_free() there might be still one kworker queued on dc->writeback_write_wq to execute write_dirty() again. 6) Now this kworker is scheduled on dc->writeback_write_wq to run by process_one_work() (which is called by worker_thread()). Before calling the kwork routine, wq->lockdep_map is acquired. 7) But wq->lockdep_map is acquired already in step 4), so a A-A lock (lockdep terminology) scenario happens. Indeed on multiple cores syatem, the above deadlock is very rare to happen, just as the code comments in process_one_work() says, 2263 * AFAICT there is no possible deadlock scenario between the 2264 * flush_work() and complete() primitives (except for single-threaded 2265 * workqueues), so hiding them isn't a problem. But it is still good to fix such lockdep warning, even no one running bcache on single core system. The fix is simple. This patch solves the above potential deadlock by, - Do not destroy workqueue dc->writeback_write_wq in cached_dev_free(). - Flush and destroy dc->writeback_write_wq in writebach kthread routine bch_writeback_thread(), where after quit the thread main while-loop and before cached_dev_put() is called. By this fix, dc->writeback_write_wq will be stopped and destroy before the writeback kthread stopped, so the chance for a A-A locking on wq->lockdep_map is disappeared, such A-A deadlock won't happen any more. Signed-off-by: Coly Li Signed-off-by: Jens Axboe Signed-off-by: Sasha Levin

bcache: check c->gc_thread by IS_ERR_OR_NULL in cache_set_flush()

2019-07-26T07:12:46Z

[ Upstream commit b387e9b58679c60f5b1e4313939bd4878204fc37 ] When system memory is in heavy pressure, bch_gc_thread_start() from run_cache_set() may fail due to out of memory. In such condition, c->gc_thread is assigned to -ENOMEM, not NULL pointer. Then in following failure code path bch_cache_set_error(), when cache_set_flush() gets called, the code piece to stop c->gc_thread is broken, if (!IS_ERR_OR_NULL(c->gc_thread)) kthread_stop(c->gc_thread); And KASAN catches such NULL pointer deference problem, with the warning information: [ 561.207881] ================================================================== [ 561.207900] BUG: KASAN: null-ptr-deref in kthread_stop+0x3b/0x440 [ 561.207904] Write of size 4 at addr 000000000000001c by task kworker/15:1/313 [ 561.207913] CPU: 15 PID: 313 Comm: kworker/15:1 Tainted: G W 5.0.0-vanilla+ #3 [ 561.207916] Hardware name: Lenovo ThinkSystem SR650 -[7X05CTO1WW]-/-[7X05CTO1WW]-, BIOS -[IVE136T-2.10]- 03/22/2019 [ 561.207935] Workqueue: events cache_set_flush [bcache] [ 561.207940] Call Trace: [ 561.207948] dump_stack+0x9a/0xeb [ 561.207955] ? kthread_stop+0x3b/0x440 [ 561.207960] ? kthread_stop+0x3b/0x440 [ 561.207965] kasan_report+0x176/0x192 [ 561.207973] ? kthread_stop+0x3b/0x440 [ 561.207981] kthread_stop+0x3b/0x440 [ 561.207995] cache_set_flush+0xd4/0x6d0 [bcache] [ 561.208008] process_one_work+0x856/0x1620 [ 561.208015] ? find_held_lock+0x39/0x1d0 [ 561.208028] ? drain_workqueue+0x380/0x380 [ 561.208048] worker_thread+0x87/0xb80 [ 561.208058] ? __kthread_parkme+0xb6/0x180 [ 561.208067] ? process_one_work+0x1620/0x1620 [ 561.208072] kthread+0x326/0x3e0 [ 561.208079] ? kthread_create_worker_on_cpu+0xc0/0xc0 [ 561.208090] ret_from_fork+0x3a/0x50 [ 561.208110] ================================================================== [ 561.208113] Disabling lock debugging due to kernel taint [ 561.208115] irq event stamp: 11800231 [ 561.208126] hardirqs last enabled at (11800231): [] do_syscall_64+0x18/0x410 [ 561.208127] BUG: unable to handle kernel NULL pointer dereference at 000000000000001c [ 561.208129] #PF error: [WRITE] [ 561.312253] hardirqs last disabled at (11800230): [] trace_hardirqs_off_thunk+0x1a/0x1c [ 561.312259] softirqs last enabled at (11799832): [] __do_softirq+0x5c7/0x8c3 [ 561.405975] PGD 0 P4D 0 [ 561.442494] softirqs last disabled at (11799821): [] irq_exit+0x1ac/0x1e0 [ 561.791359] Oops: 0002 [#1] SMP KASAN NOPTI [ 561.791362] CPU: 15 PID: 313 Comm: kworker/15:1 Tainted: G B W 5.0.0-vanilla+ #3 [ 561.791363] Hardware name: Lenovo ThinkSystem SR650 -[7X05CTO1WW]-/-[7X05CTO1WW]-, BIOS -[IVE136T-2.10]- 03/22/2019 [ 561.791371] Workqueue: events cache_set_flush [bcache] [ 561.791374] RIP: 0010:kthread_stop+0x3b/0x440 [ 561.791376] Code: 00 00 65 8b 05 26 d5 e0 7c 89 c0 48 0f a3 05 ec aa df 02 0f 82 dc 02 00 00 4c 8d 63 20 be 04 00 00 00 4c 89 e7 e8 65 c5 53 00 ff 43 20 48 8d 7b 24 48 b8 00 00 00 00 00 fc ff df 48 89 fa 48 [ 561.791377] RSP: 0018:ffff88872fc8fd10 EFLAGS: 00010286 [ 561.838895] bcache: bch_count_io_errors() nvme0n1: IO error on writing btree. [ 561.838916] bcache: bch_count_io_errors() nvme0n1: IO error on writing btree. [ 561.838934] bcache: bch_count_io_errors() nvme0n1: IO error on writing btree. [ 561.838948] bcache: bch_count_io_errors() nvme0n1: IO error on writing btree. [ 561.838966] bcache: bch_count_io_errors() nvme0n1: IO error on writing btree. [ 561.838979] bcache: bch_count_io_errors() nvme0n1: IO error on writing btree. [ 561.838996] bcache: bch_count_io_errors() nvme0n1: IO error on writing btree. [ 563.067028] RAX: 0000000000000000 RBX: fffffffffffffffc RCX: ffffffff832dd314 [ 563.067030] RDX: 0000000000000000 RSI: 0000000000000004 RDI: 0000000000000297 [ 563.067032] RBP: ffff88872fc8fe88 R08: fffffbfff0b8213d R09: fffffbfff0b8213d [ 563.067034] R10: 0000000000000001 R11: fffffbfff0b8213c R12: 000000000000001c [ 563.408618] R13: ffff88dc61cc0f68 R14: ffff888102b94900 R15: ffff88dc61cc0f68 [ 563.408620] FS: 0000000000000000(0000) GS:ffff888f7dc00000(0000) knlGS:0000000000000000 [ 563.408622] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 [ 563.408623] CR2: 000000000000001c CR3: 0000000f48a1a004 CR4: 00000000007606e0 [ 563.408625] DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 [ 563.408627] DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400 [ 563.904795] bcache: bch_count_io_errors() nvme0n1: IO error on writing btree. [ 563.915796] PKRU: 55555554 [ 563.915797] Call Trace: [ 563.915807] cache_set_flush+0xd4/0x6d0 [bcache] [ 563.915812] process_one_work+0x856/0x1620 [ 564.001226] bcache: bch_count_io_errors() nvme0n1: IO error on writing btree. [ 564.033563] ? find_held_lock+0x39/0x1d0 [ 564.033567] ? drain_workqueue+0x380/0x380 [ 564.033574] worker_thread+0x87/0xb80 [ 564.062823] bcache: bch_count_io_errors() nvme0n1: IO error on writing btree. [ 564.118042] ? __kthread_parkme+0xb6/0x180 [ 564.118046] ? process_one_work+0x1620/0x1620 [ 564.118048] kthread+0x326/0x3e0 [ 564.118050] ? kthread_create_worker_on_cpu+0xc0/0xc0 [ 564.167066] bcache: bch_count_io_errors() nvme0n1: IO error on writing btree. [ 564.252441] ret_from_fork+0x3a/0x50 [ 564.252447] Modules linked in: msr rpcrdma sunrpc rdma_ucm ib_iser ib_umad rdma_cm ib_ipoib i40iw configfs iw_cm ib_cm libiscsi scsi_transport_iscsi mlx4_ib ib_uverbs mlx4_en ib_core nls_iso8859_1 nls_cp437 vfat fat intel_rapl skx_edac x86_pkg_temp_thermal coretemp iTCO_wdt iTCO_vendor_support crct10dif_pclmul crc32_pclmul crc32c_intel ghash_clmulni_intel ses raid0 aesni_intel cdc_ether enclosure usbnet ipmi_ssif joydev aes_x86_64 i40e scsi_transport_sas mii bcache md_mod crypto_simd mei_me ioatdma crc64 ptp cryptd pcspkr i2c_i801 mlx4_core glue_helper pps_core mei lpc_ich dca wmi ipmi_si ipmi_devintf nd_pmem dax_pmem nd_btt ipmi_msghandler device_dax pcc_cpufreq button hid_generic usbhid mgag200 i2c_algo_bit drm_kms_helper syscopyarea sysfillrect xhci_pci sysimgblt fb_sys_fops xhci_hcd ttm megaraid_sas drm usbcore nfit libnvdimm sg dm_multipath dm_mod scsi_dh_rdac scsi_dh_emc scsi_dh_alua efivarfs [ 564.299390] bcache: bch_count_io_errors() nvme0n1: IO error on writing btree. [ 564.348360] CR2: 000000000000001c [ 564.348362] ---[ end trace b7f0e5cc7b2103b0 ]--- Therefore, it is not enough to only check whether c->gc_thread is NULL, we should use IS_ERR_OR_NULL() to check both NULL pointer and error value. This patch changes the above buggy code piece in this way, if (!IS_ERR_OR_NULL(c->gc_thread)) kthread_stop(c->gc_thread); Signed-off-by: Coly Li Signed-off-by: Jens Axboe Signed-off-by: Sasha Levin

bcache: acquire bch_register_lock later in cached_dev_free()

2019-07-26T07:12:46Z

[ Upstream commit 80265d8dfd77792e133793cef44a21323aac2908 ] When enable lockdep engine, a lockdep warning can be observed when reboot or shutdown system, [ 3142.764557][ T1] bcache: bcache_reboot() Stopping all devices: [ 3142.776265][ T2649] [ 3142.777159][ T2649] ====================================================== [ 3142.780039][ T2649] WARNING: possible circular locking dependency detected [ 3142.782869][ T2649] 5.2.0-rc4-lp151.20-default+ #1 Tainted: G W [ 3142.785684][ T2649] ------------------------------------------------------ [ 3142.788479][ T2649] kworker/3:67/2649 is trying to acquire lock: [ 3142.790738][ T2649] 00000000aaf02291 ((wq_completion)bcache_writeback_wq){+.+.}, at: flush_workqueue+0x87/0x4c0 [ 3142.794678][ T2649] [ 3142.794678][ T2649] but task is already holding lock: [ 3142.797402][ T2649] 000000004fcf89c5 (&bch_register_lock){+.+.}, at: cached_dev_free+0x17/0x120 [bcache] [ 3142.801462][ T2649] [ 3142.801462][ T2649] which lock already depends on the new lock. [ 3142.801462][ T2649] [ 3142.805277][ T2649] [ 3142.805277][ T2649] the existing dependency chain (in reverse order) is: [ 3142.808902][ T2649] [ 3142.808902][ T2649] -> #2 (&bch_register_lock){+.+.}: [ 3142.812396][ T2649] __mutex_lock+0x7a/0x9d0 [ 3142.814184][ T2649] cached_dev_free+0x17/0x120 [bcache] [ 3142.816415][ T2649] process_one_work+0x2a4/0x640 [ 3142.818413][ T2649] worker_thread+0x39/0x3f0 [ 3142.820276][ T2649] kthread+0x125/0x140 [ 3142.822061][ T2649] ret_from_fork+0x3a/0x50 [ 3142.823965][ T2649] [ 3142.823965][ T2649] -> #1 ((work_completion)(&cl->work)#2){+.+.}: [ 3142.827244][ T2649] process_one_work+0x277/0x640 [ 3142.829160][ T2649] worker_thread+0x39/0x3f0 [ 3142.830958][ T2649] kthread+0x125/0x140 [ 3142.832674][ T2649] ret_from_fork+0x3a/0x50 [ 3142.834915][ T2649] [ 3142.834915][ T2649] -> #0 ((wq_completion)bcache_writeback_wq){+.+.}: [ 3142.838121][ T2649] lock_acquire+0xb4/0x1c0 [ 3142.840025][ T2649] flush_workqueue+0xae/0x4c0 [ 3142.842035][ T2649] drain_workqueue+0xa9/0x180 [ 3142.844042][ T2649] destroy_workqueue+0x17/0x250 [ 3142.846142][ T2649] cached_dev_free+0x52/0x120 [bcache] [ 3142.848530][ T2649] process_one_work+0x2a4/0x640 [ 3142.850663][ T2649] worker_thread+0x39/0x3f0 [ 3142.852464][ T2649] kthread+0x125/0x140 [ 3142.854106][ T2649] ret_from_fork+0x3a/0x50 [ 3142.855880][ T2649] [ 3142.855880][ T2649] other info that might help us debug this: [ 3142.855880][ T2649] [ 3142.859663][ T2649] Chain exists of: [ 3142.859663][ T2649] (wq_completion)bcache_writeback_wq --> (work_completion)(&cl->work)#2 --> &bch_register_lock [ 3142.859663][ T2649] [ 3142.865424][ T2649] Possible unsafe locking scenario: [ 3142.865424][ T2649] [ 3142.868022][ T2649] CPU0 CPU1 [ 3142.869885][ T2649] ---- ---- [ 3142.871751][ T2649] lock(&bch_register_lock); [ 3142.873379][ T2649] lock((work_completion)(&cl->work)#2); [ 3142.876399][ T2649] lock(&bch_register_lock); [ 3142.879727][ T2649] lock((wq_completion)bcache_writeback_wq); [ 3142.882064][ T2649] [ 3142.882064][ T2649] *** DEADLOCK *** [ 3142.882064][ T2649] [ 3142.885060][ T2649] 3 locks held by kworker/3:67/2649: [ 3142.887245][ T2649] #0: 00000000e774cdd0 ((wq_completion)events){+.+.}, at: process_one_work+0x21e/0x640 [ 3142.890815][ T2649] #1: 00000000f7df89da ((work_completion)(&cl->work)#2){+.+.}, at: process_one_work+0x21e/0x640 [ 3142.894884][ T2649] #2: 000000004fcf89c5 (&bch_register_lock){+.+.}, at: cached_dev_free+0x17/0x120 [bcache] [ 3142.898797][ T2649] [ 3142.898797][ T2649] stack backtrace: [ 3142.900961][ T2649] CPU: 3 PID: 2649 Comm: kworker/3:67 Tainted: G W 5.2.0-rc4-lp151.20-default+ #1 [ 3142.904789][ T2649] Hardware name: VMware, Inc. VMware Virtual Platform/440BX Desktop Reference Platform, BIOS 6.00 04/13/2018 [ 3142.909168][ T2649] Workqueue: events cached_dev_free [bcache] [ 3142.911422][ T2649] Call Trace: [ 3142.912656][ T2649] dump_stack+0x85/0xcb [ 3142.914181][ T2649] print_circular_bug+0x19a/0x1f0 [ 3142.916193][ T2649] __lock_acquire+0x16cd/0x1850 [ 3142.917936][ T2649] ? __lock_acquire+0x6a8/0x1850 [ 3142.919704][ T2649] ? lock_acquire+0xb4/0x1c0 [ 3142.921335][ T2649] ? find_held_lock+0x34/0xa0 [ 3142.923052][ T2649] lock_acquire+0xb4/0x1c0 [ 3142.924635][ T2649] ? flush_workqueue+0x87/0x4c0 [ 3142.926375][ T2649] flush_workqueue+0xae/0x4c0 [ 3142.928047][ T2649] ? flush_workqueue+0x87/0x4c0 [ 3142.929824][ T2649] ? drain_workqueue+0xa9/0x180 [ 3142.931686][ T2649] drain_workqueue+0xa9/0x180 [ 3142.933534][ T2649] destroy_workqueue+0x17/0x250 [ 3142.935787][ T2649] cached_dev_free+0x52/0x120 [bcache] [ 3142.937795][ T2649] process_one_work+0x2a4/0x640 [ 3142.939803][ T2649] worker_thread+0x39/0x3f0 [ 3142.941487][ T2649] ? process_one_work+0x640/0x640 [ 3142.943389][ T2649] kthread+0x125/0x140 [ 3142.944894][ T2649] ? kthread_create_worker_on_cpu+0x70/0x70 [ 3142.947744][ T2649] ret_from_fork+0x3a/0x50 [ 3142.970358][ T2649] bcache: bcache_device_free() bcache0 stopped Here is how the deadlock happens. 1) bcache_reboot() calls bcache_device_stop(), then inside bcache_device_stop() BCACHE_DEV_CLOSING bit is set on d->flags. Then closure_queue(&d->cl) is called to invoke cached_dev_flush(). 2) In cached_dev_flush(), cached_dev_free() is called by continu_at(). 3) In cached_dev_free(), when stopping the writeback kthread of the cached device by kthread_stop(), dc->writeback_thread will be waken up to quite the kthread while-loop, then cached_dev_put() is called in bch_writeback_thread(). 4) Calling cached_dev_put() in writeback kthread may drop dc->count to 0, then dc->detach kworker is scheduled, which is initialized as cached_dev_detach_finish(). 5) Inside cached_dev_detach_finish(), the last line of code is to call closure_put(&dc->disk.cl), which drops the last reference counter of closrure dc->disk.cl, then the callback cached_dev_flush() gets called. Now cached_dev_flush() is called for second time in the code path, the first time is in step 2). And again bch_register_lock will be acquired again, and a A-A lock (lockdep terminology) is happening. The root cause of the above A-A lock is in cached_dev_free(), mutex bch_register_lock is held before stopping writeback kthread and other kworkers. Fortunately now we have variable 'bcache_is_reboot', which may prevent device registration or unregistration during reboot/shutdown time, so it is unncessary to hold bch_register_lock such early now. This is how this patch fixes the reboot/shutdown time A-A lock issue: After moving mutex_lock(&bch_register_lock) to a later location where before atomic_read(&dc->running) in cached_dev_free(), such A-A lock problem can be solved without any reboot time registration race. Signed-off-by: Coly Li Signed-off-by: Jens Axboe Signed-off-by: Sasha Levin

bcache: add failure check to run_cache_set() for journal replay

2019-05-31T13:43:24Z

[ Upstream commit ce3e4cfb59cb382f8e5ce359238aa580d4ae7778 ] Currently run_cache_set() has no return value, if there is failure in bch_journal_replay(), the caller of run_cache_set() has no idea about such failure and just continue to execute following code after run_cache_set(). The internal failure is triggered inside bch_journal_replay() and being handled in async way. This behavior is inefficient, while failure handling inside bch_journal_replay(), cache register code is still running to start the cache set. Registering and unregistering code running as same time may introduce some rare race condition, and make the code to be more hard to be understood. This patch adds return value to run_cache_set(), and returns -EIO if bch_journal_rreplay() fails. Then caller of run_cache_set() may detect such failure and stop registering code flow immedidately inside register_cache_set(). If journal replay fails, run_cache_set() can report error immediately to register_cache_set(). This patch makes the failure handling for bch_journal_replay() be in synchronized way, easier to understand and debug, and avoid poetential race condition for register-and-unregister in same time. Signed-off-by: Coly Li Signed-off-by: Jens Axboe Signed-off-by: Sasha Levin

bcache: avoid potential memleak of list of journal_replay(s) in the CACHE_SYNC branch of run_cache_set

2019-05-31T13:43:24Z

[ Upstream commit 95f18c9d1310730d075499a75aaf13bcd60405a7 ] In the CACHE_SYNC branch of run_cache_set(), LIST_HEAD(journal) is used to collect journal_replay(s) and filled by bch_journal_read(). If all goes well, bch_journal_replay() will release the list of jounal_replay(s) at the end of the branch. If something goes wrong, code flow will jump to the label "err:" and leave the list unreleased. This patch will release the list of journal_replay(s) in the case of error detected. v1 -> v2: * Move the release code to the location after label 'err:' to simply the change. Signed-off-by: Shenghui Wang Signed-off-by: Coly Li Signed-off-by: Jens Axboe Signed-off-by: Sasha Levin

bcache: fix a race between cache register and cacheset unregister

2019-05-22T05:39:54Z

commit a4b732a248d12cbdb46999daf0bf288c011335eb upstream. There is a race between cache device register and cache set unregister. For an already registered cache device, register_bcache will call bch_is_open to iterate through all cachesets and check every cache there. The race occurs if cache_set_free executes at the same time and clears the caches right before ca is dereferenced in bch_is_open_cache. To close the race, let's make sure the clean up work is protected by the bch_register_lock as well. This issue can be reproduced as follows, while true; do echo /dev/XXX> /sys/fs/bcache/register ; done& while true; do echo 1> /sys/block/XXX/bcache/set/unregister ; done & and results in the following oops, [ +0.000053] BUG: unable to handle kernel NULL pointer dereference at 0000000000000998 [ +0.000457] #PF error: [normal kernel read fault] [ +0.000464] PGD 800000003ca9d067 P4D 800000003ca9d067 PUD 3ca9c067 PMD 0 [ +0.000388] Oops: 0000 [#1] SMP PTI [ +0.000269] CPU: 1 PID: 3266 Comm: bash Not tainted 5.0.0+ #6 [ +0.000346] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.11.0-2.fc28 04/01/2014 [ +0.000472] RIP: 0010:register_bcache+0x1829/0x1990 [bcache] [ +0.000344] Code: b0 48 83 e8 50 48 81 fa e0 e1 10 c0 0f 84 a9 00 00 00 48 89 c6 48 89 ca 0f b7 ba 54 04 00 00 4c 8b 82 60 0c 00 00 85 ff 74 2f <49> 3b a8 98 09 00 00 74 4e 44 8d 47 ff 31 ff 49 c1 e0 03 eb 0d [ +0.000839] RSP: 0018:ffff92ee804cbd88 EFLAGS: 00010202 [ +0.000328] RAX: ffffffffc010e190 RBX: ffff918b5c6b5000 RCX: ffff918b7d8e0000 [ +0.000399] RDX: ffff918b7d8e0000 RSI: ffffffffc010e190 RDI: 0000000000000001 [ +0.000398] RBP: ffff918b7d318340 R08: 0000000000000000 R09: ffffffffb9bd2d7a [ +0.000385] R10: ffff918b7eb253c0 R11: ffffb95980f51200 R12: ffffffffc010e1a0 [ +0.000411] R13: fffffffffffffff2 R14: 000000000000000b R15: ffff918b7e232620 [ +0.000384] FS: 00007f955bec2740(0000) GS:ffff918b7eb00000(0000) knlGS:0000000000000000 [ +0.000420] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 [ +0.000801] CR2: 0000000000000998 CR3: 000000003cad6000 CR4: 00000000001406e0 [ +0.000837] Call Trace: [ +0.000682] ? _cond_resched+0x10/0x20 [ +0.000691] ? __kmalloc+0x131/0x1b0 [ +0.000710] kernfs_fop_write+0xfa/0x170 [ +0.000733] __vfs_write+0x2e/0x190 [ +0.000688] ? inode_security+0x10/0x30 [ +0.000698] ? selinux_file_permission+0xd2/0x120 [ +0.000752] ? security_file_permission+0x2b/0x100 [ +0.000753] vfs_write+0xa8/0x1a0 [ +0.000676] ksys_write+0x4d/0xb0 [ +0.000699] do_syscall_64+0x3a/0xf0 [ +0.000692] entry_SYSCALL_64_after_hwframe+0x44/0xa9 Signed-off-by: Liang Chen Cc: stable@vger.kernel.org Signed-off-by: Coly Li Signed-off-by: Jens Axboe Signed-off-by: Greg Kroah-Hartman

bcache: fix indentation issue, remove tabs on a hunk of code

2019-02-09T14:18:31Z

There is a hunk of code that is indented one level too deep, fix this by removing the extra tabs. Signed-off-by: Colin Ian King Signed-off-by: Coly Li Signed-off-by: Jens Axboe

bcache: make cutoff_writeback and cutoff_writeback_sync tunable

2018-12-13T15:15:54Z

Currently the cutoff writeback and cutoff writeback sync thresholds are defined by CUTOFF_WRITEBACK (40) and CUTOFF_WRITEBACK_SYNC (70) as static values. Most of time these they work fine, but when people want to do research on bcache writeback mode performance tuning, there is no chance to modify the soft and hard cutoff writeback values. This patch introduces two module parameters bch_cutoff_writeback_sync and bch_cutoff_writeback which permit people to tune the values when loading bcache.ko. If they are not specified by module loading, current values CUTOFF_WRITEBACK_SYNC and CUTOFF_WRITEBACK will be used as default and nothing changes. When people want to tune this two values, - cutoff_writeback can be set in range [1, 70] - cutoff_writeback_sync can be set in range [1, 90] - cutoff_writeback always <= cutoff_writeback_sync The default values are strongly recommended to most of users for most of workloads. Anyway, if people wants to take their own risk to do research on new writeback cutoff tuning for their own workload, now they can make it. Signed-off-by: Coly Li Signed-off-by: Jens Axboe

bcache: add MODULE_DESCRIPTION information

2018-12-13T15:15:54Z

This patch moves MODULE_AUTHOR and MODULE_LICENSE to end of super.c, and add MODULE_DESCRIPTION("Bcache: a Linux block layer cache"). This is preparation for adding module parameters. Signed-off-by: Coly Li Signed-off-by: Jens Axboe