From fee13fe96529523a709d1fff487f14a5e0d56d34 Mon Sep 17 00:00:00 2001 From: Dennis Zhou Date: Fri, 17 May 2019 19:16:26 -0400 Subject: [PATCH] btrfs: correct zstd workspace manager lock to use spin_lock_bh() The btrfs zstd workspace manager uses a background timer to reclaim not recently used workspaces. I used spin_lock() from this context which should have been caught with lockdep, but was not. This deadlock was reported in bugzilla. The fix is to switch the zstd wsm lock to use spin_lock_bh() from the softirq context. This happened quite relibably on ppc64, unlike on other architectures. [ 313.402874] ================================ [ 313.402875] WARNING: inconsistent lock state [ 313.402879] 5.1.0-rc7 #1 Not tainted [ 313.402880] -------------------------------- [ 313.402882] inconsistent {SOFTIRQ-ON-W} -> {IN-SOFTIRQ-W} usage. [ 313.402885] swapper/5/0 [HC0[0]:SC1[1]:HE1:SE0] takes: [ 313.402888] 0000000080d1120c (&(&wsm.lock)->rlock){+.?.}, at: .zstd_reclaim_timer_fn+0x40/0x230 [ 313.402895] {SOFTIRQ-ON-W} state was registered at: [ 313.402899] .lock_acquire+0xd0/0x240 [ 313.402903] ._raw_spin_lock+0x34/0x60 [ 313.402906] .zstd_get_workspace+0xd0/0x360 [ 313.402908] .end_compressed_bio_read+0x3b8/0x540 [ 313.402911] .bio_endio+0x174/0x2c0 [ 313.402914] .end_workqueue_fn+0x4c/0x70 [ 313.402917] .normal_work_helper+0x138/0x7e0 [ 313.402920] .process_one_work+0x324/0x790 [ 313.402922] .worker_thread+0x68/0x570 [ 313.402925] .kthread+0x19c/0x1b0 [ 313.402928] .ret_from_kernel_thread+0x58/0x78 [ 313.402930] irq event stamp: 2629216 [ 313.402933] hardirqs last enabled at (2629216): [] ._raw_spin_unlock_irq+0x38/0x60 [ 313.402936] hardirqs last disabled at (2629215): [] ._raw_spin_lock_irq+0x24/0x70 [ 313.402939] softirqs last enabled at (2629212): [] .irq_enter+0x8c/0xd0 [ 313.402942] softirqs last disabled at (2629213): [] .irq_exit+0x118/0x170 [ 313.402944] other info that might help us debug this: [ 313.402945] Possible unsafe locking scenario: [ 313.402947] CPU0 [ 313.402948] ---- [ 313.402949] lock(&(&wsm.lock)->rlock); [ 313.402951] [ 313.402952] lock(&(&wsm.lock)->rlock); [ 313.402954] *** DEADLOCK *** [ 313.402957] 1 lock held by swapper/5/0: [ 313.402958] #0: 000000004b612042 ((&wsm.timer)){+.-.}, at: .call_timer_fn+0x0/0x3c0 [ 313.402963] stack backtrace: [ 313.402967] CPU: 5 PID: 0 Comm: swapper/5 Not tainted 5.1.0-rc7 #1 [ 313.402968] Call Trace: [ 313.402972] [c0000007fa262e70] [c0000000009b3294] .dump_stack+0xe0/0x15c (unreliable) [ 313.402975] [c0000007fa262f10] [c000000000125548] .print_usage_bug+0x348/0x390 [ 313.402978] [c0000007fa262fd0] [c000000000125cb4] .mark_lock+0x724/0x930 [ 313.402981] [c0000007fa263080] [c000000000126c20] .__lock_acquire+0xc90/0x16a0 [ 313.402984] [c0000007fa2631b0] [c000000000128040] .lock_acquire+0xd0/0x240 [ 313.402987] [c0000007fa263280] [c0000000009da2b4] ._raw_spin_lock+0x34/0x60 [ 313.402990] [c0000007fa263300] [c00000000054b0b0] .zstd_reclaim_timer_fn+0x40/0x230 [ 313.402993] [c0000007fa2633d0] [c000000000158b38] .call_timer_fn+0xc8/0x3c0 [ 313.402996] [c0000007fa2634a0] [c000000000158f74] .expire_timers+0x144/0x260 [ 313.402999] [c0000007fa263550] [c000000000159178] .run_timer_softirq+0xe8/0x230 [ 313.403002] [c0000007fa263680] [c0000000009db288] .__do_softirq+0x188/0x5d4 [ 313.403004] [c0000007fa263790] [c0000000000afb58] .irq_exit+0x118/0x170 [ 313.403008] [c0000007fa263800] [c000000000028d88] .timer_interrupt+0x158/0x430 [ 313.403012] [c0000007fa2638b0] [c0000000000091d4] decrementer_common+0x134/0x140 [ 313.403017] --- interrupt: 901 at replay_interrupt_return+0x0/0x4 LR = .arch_local_irq_restore.part.0+0x68/0x80 [ 313.403020] [c0000007fa263bb0] [c00000000001a3ac] .arch_local_irq_restore.part.0+0x2c/0x80 (unreliable) [ 313.403024] [c0000007fa263c30] [c0000000007bbbcc] .cpuidle_enter_state+0xec/0x670 [ 313.403027] [c0000007fa263d00] [c0000000000f5130] .call_cpuidle+0x40/0x90 [ 313.403031] [c0000007fa263d70] [c0000000000f554c] .do_idle+0x2dc/0x3a0 [ 313.403034] [c0000007fa263e30] [c0000000000f59ac] .cpu_startup_entry+0x2c/0x30 [ 313.403037] [c0000007fa263ea0] [c000000000045674] .start_secondary+0x644/0x650 [ 313.403041] [c0000007fa263f90] [c00000000000ad5c] start_secondary_prolog+0x10/0x14 Bugzilla: https://bugzilla.kernel.org/show_bug.cgi?id=203517 Fixes: 3f93aef535c8 ("btrfs: add zstd compression level support") CC: stable@vger.kernel.org # 5.1+ Signed-off-by: Dennis Zhou Reviewed-by: David Sterba Signed-off-by: David Sterba --- fs/btrfs/zstd.c | 20 ++++++++++---------- 1 file changed, 10 insertions(+), 10 deletions(-) diff --git a/fs/btrfs/zstd.c b/fs/btrfs/zstd.c index a6ff07cf11d5..3837ca180d52 100644 --- a/fs/btrfs/zstd.c +++ b/fs/btrfs/zstd.c @@ -105,10 +105,10 @@ static void zstd_reclaim_timer_fn(struct timer_list *timer) unsigned long reclaim_threshold = jiffies - ZSTD_BTRFS_RECLAIM_JIFFIES; struct list_head *pos, *next; - spin_lock(&wsm.lock); + spin_lock_bh(&wsm.lock); if (list_empty(&wsm.lru_list)) { - spin_unlock(&wsm.lock); + spin_unlock_bh(&wsm.lock); return; } @@ -137,7 +137,7 @@ static void zstd_reclaim_timer_fn(struct timer_list *timer) if (!list_empty(&wsm.lru_list)) mod_timer(&wsm.timer, jiffies + ZSTD_BTRFS_RECLAIM_JIFFIES); - spin_unlock(&wsm.lock); + spin_unlock_bh(&wsm.lock); } /* @@ -198,7 +198,7 @@ static void zstd_cleanup_workspace_manager(void) struct workspace *workspace; int i; - spin_lock(&wsm.lock); + spin_lock_bh(&wsm.lock); for (i = 0; i < ZSTD_BTRFS_MAX_LEVEL; i++) { while (!list_empty(&wsm.idle_ws[i])) { workspace = container_of(wsm.idle_ws[i].next, @@ -208,7 +208,7 @@ static void zstd_cleanup_workspace_manager(void) zstd_free_workspace(&workspace->list); } } - spin_unlock(&wsm.lock); + spin_unlock_bh(&wsm.lock); del_timer_sync(&wsm.timer); } @@ -230,7 +230,7 @@ static struct list_head *zstd_find_workspace(unsigned int level) struct workspace *workspace; int i = level - 1; - spin_lock(&wsm.lock); + spin_lock_bh(&wsm.lock); for_each_set_bit_from(i, &wsm.active_map, ZSTD_BTRFS_MAX_LEVEL) { if (!list_empty(&wsm.idle_ws[i])) { ws = wsm.idle_ws[i].next; @@ -242,11 +242,11 @@ static struct list_head *zstd_find_workspace(unsigned int level) list_del(&workspace->lru_list); if (list_empty(&wsm.idle_ws[i])) clear_bit(i, &wsm.active_map); - spin_unlock(&wsm.lock); + spin_unlock_bh(&wsm.lock); return ws; } } - spin_unlock(&wsm.lock); + spin_unlock_bh(&wsm.lock); return NULL; } @@ -305,7 +305,7 @@ static void zstd_put_workspace(struct list_head *ws) { struct workspace *workspace = list_to_workspace(ws); - spin_lock(&wsm.lock); + spin_lock_bh(&wsm.lock); /* A node is only taken off the lru if we are the corresponding level */ if (workspace->req_level == workspace->level) { @@ -325,7 +325,7 @@ static void zstd_put_workspace(struct list_head *ws) list_add(&workspace->list, &wsm.idle_ws[workspace->level - 1]); workspace->req_level = 0; - spin_unlock(&wsm.lock); + spin_unlock_bh(&wsm.lock); if (workspace->level == ZSTD_BTRFS_MAX_LEVEL) cond_wake_up(&wsm.wait);