queue-5.1/btrfs-correct-zstd-workspace-manager-lock-to-use-spin_lock_bh.patch

   1 From fee13fe96529523a709d1fff487f14a5e0d56d34 Mon Sep 17 00:00:00 2001
   2 From: Dennis Zhou <dennis@kernel.org>
   3 Date: Fri, 17 May 2019 19:16:26 -0400
   4 Subject: btrfs: correct zstd workspace manager lock to use spin_lock_bh()
   5
   6 From: Dennis Zhou <dennis@kernel.org>
   7
   8 commit fee13fe96529523a709d1fff487f14a5e0d56d34 upstream.
   9
  10 The btrfs zstd workspace manager uses a background timer to reclaim not
  11 recently used workspaces. I used spin_lock() from this context which
  12 should have been caught with lockdep, but was not. This deadlock was
  13 reported in bugzilla. The fix is to switch the zstd wsm lock to use
  14 spin_lock_bh() from the softirq context.
  15
  16 This happened quite relibably on ppc64, unlike on other architectures.
  17
  18   [  313.402874] ================================
  19   [  313.402875] WARNING: inconsistent lock state
  20   [  313.402879] 5.1.0-rc7 #1 Not tainted
  21   [  313.402880] --------------------------------
  22   [  313.402882] inconsistent {SOFTIRQ-ON-W} -> {IN-SOFTIRQ-W} usage.
  23   [  313.402885] swapper/5/0 [HC0[0]:SC1[1]:HE1:SE0] takes:
  24   [  313.402888] 0000000080d1120c (&(&wsm.lock)->rlock){+.?.}, at: .zstd_reclaim_timer_fn+0x40/0x230
  25   [  313.402895] {SOFTIRQ-ON-W} state was registered at:
  26   [  313.402899]   .lock_acquire+0xd0/0x240
  27   [  313.402903]   ._raw_spin_lock+0x34/0x60
  28   [  313.402906]   .zstd_get_workspace+0xd0/0x360
  29   [  313.402908]   .end_compressed_bio_read+0x3b8/0x540
  30   [  313.402911]   .bio_endio+0x174/0x2c0
  31   [  313.402914]   .end_workqueue_fn+0x4c/0x70
  32   [  313.402917]   .normal_work_helper+0x138/0x7e0
  33   [  313.402920]   .process_one_work+0x324/0x790
  34   [  313.402922]   .worker_thread+0x68/0x570
  35   [  313.402925]   .kthread+0x19c/0x1b0
  36   [  313.402928]   .ret_from_kernel_thread+0x58/0x78
  37   [  313.402930] irq event stamp: 2629216
  38   [  313.402933] hardirqs last  enabled at (2629216): [<c0000000009da738>] ._raw_spin_unlock_irq+0x38/0x60
  39   [  313.402936] hardirqs last disabled at (2629215): [<c0000000009da4c4>] ._raw_spin_lock_irq+0x24/0x70
  40   [  313.402939] softirqs last  enabled at (2629212): [<c0000000000af9fc>] .irq_enter+0x8c/0xd0
  41   [  313.402942] softirqs last disabled at (2629213): [<c0000000000afb58>] .irq_exit+0x118/0x170
  42   [  313.402944]
  43                  other info that might help us debug this:
  44   [  313.402945]  Possible unsafe locking scenario:
  45
  46   [  313.402947]        CPU0
  47   [  313.402948]        ----
  48   [  313.402949]   lock(&(&wsm.lock)->rlock);
  49   [  313.402951]   <Interrupt>
  50   [  313.402952]     lock(&(&wsm.lock)->rlock);
  51   [  313.402954]
  52                   *** DEADLOCK ***
  53
  54   [  313.402957] 1 lock held by swapper/5/0:
  55   [  313.402958]  #0: 000000004b612042 ((&wsm.timer)){+.-.}, at: .call_timer_fn+0x0/0x3c0
  56   [  313.402963]
  57                  stack backtrace:
  58   [  313.402967] CPU: 5 PID: 0 Comm: swapper/5 Not tainted 5.1.0-rc7 #1
  59   [  313.402968] Call Trace:
  60   [  313.402972] [c0000007fa262e70] [c0000000009b3294] .dump_stack+0xe0/0x15c (unreliable)
  61   [  313.402975] [c0000007fa262f10] [c000000000125548] .print_usage_bug+0x348/0x390
  62   [  313.402978] [c0000007fa262fd0] [c000000000125cb4] .mark_lock+0x724/0x930
  63   [  313.402981] [c0000007fa263080] [c000000000126c20] .__lock_acquire+0xc90/0x16a0
  64   [  313.402984] [c0000007fa2631b0] [c000000000128040] .lock_acquire+0xd0/0x240
  65   [  313.402987] [c0000007fa263280] [c0000000009da2b4] ._raw_spin_lock+0x34/0x60
  66   [  313.402990] [c0000007fa263300] [c00000000054b0b0] .zstd_reclaim_timer_fn+0x40/0x230
  67   [  313.402993] [c0000007fa2633d0] [c000000000158b38] .call_timer_fn+0xc8/0x3c0
  68   [  313.402996] [c0000007fa2634a0] [c000000000158f74] .expire_timers+0x144/0x260
  69   [  313.402999] [c0000007fa263550] [c000000000159178] .run_timer_softirq+0xe8/0x230
  70   [  313.403002] [c0000007fa263680] [c0000000009db288] .__do_softirq+0x188/0x5d4
  71   [  313.403004] [c0000007fa263790] [c0000000000afb58] .irq_exit+0x118/0x170
  72   [  313.403008] [c0000007fa263800] [c000000000028d88] .timer_interrupt+0x158/0x430
  73   [  313.403012] [c0000007fa2638b0] [c0000000000091d4] decrementer_common+0x134/0x140
  74   [  313.403017] --- interrupt: 901 at replay_interrupt_return+0x0/0x4
  75                      LR = .arch_local_irq_restore.part.0+0x68/0x80
  76   [  313.403020] [c0000007fa263bb0] [c00000000001a3ac] .arch_local_irq_restore.part.0+0x2c/0x80 (unreliable)
  77   [  313.403024] [c0000007fa263c30] [c0000000007bbbcc] .cpuidle_enter_state+0xec/0x670
  78   [  313.403027] [c0000007fa263d00] [c0000000000f5130] .call_cpuidle+0x40/0x90
  79   [  313.403031] [c0000007fa263d70] [c0000000000f554c] .do_idle+0x2dc/0x3a0
  80   [  313.403034] [c0000007fa263e30] [c0000000000f59ac] .cpu_startup_entry+0x2c/0x30
  81   [  313.403037] [c0000007fa263ea0] [c000000000045674] .start_secondary+0x644/0x650
  82   [  313.403041] [c0000007fa263f90] [c00000000000ad5c] start_secondary_prolog+0x10/0x14
  83
  84 Bugzilla: https://bugzilla.kernel.org/show_bug.cgi?id=203517
  85 Fixes: 3f93aef535c8 ("btrfs: add zstd compression level support")
  86 CC: stable@vger.kernel.org # 5.1+
  87 Signed-off-by: Dennis Zhou <dennis@kernel.org>
  88 Reviewed-by: David Sterba <dsterba@suse.com>
  89 Signed-off-by: David Sterba <dsterba@suse.com>
  90 Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
  91
  92 ---
  93  fs/btrfs/zstd.c |   20 ++++++++++----------
  94  1 file changed, 10 insertions(+), 10 deletions(-)
  95
  96 --- a/fs/btrfs/zstd.c
  97 +++ b/fs/btrfs/zstd.c
  98 @@ -102,10 +102,10 @@ static void zstd_reclaim_timer_fn(struct
  99         unsigned long reclaim_threshold = jiffies - ZSTD_BTRFS_RECLAIM_JIFFIES;
 100         struct list_head *pos, *next;
 101
 102 -       spin_lock(&wsm.lock);
 103 +       spin_lock_bh(&wsm.lock);
 104
 105         if (list_empty(&wsm.lru_list)) {
 106 -               spin_unlock(&wsm.lock);
 107 +               spin_unlock_bh(&wsm.lock);
 108                 return;
 109         }
 110
 111 @@ -134,7 +134,7 @@ static void zstd_reclaim_timer_fn(struct
 112         if (!list_empty(&wsm.lru_list))
 113                 mod_timer(&wsm.timer, jiffies + ZSTD_BTRFS_RECLAIM_JIFFIES);
 114
 115 -       spin_unlock(&wsm.lock);
 116 +       spin_unlock_bh(&wsm.lock);
 117  }
 118
 119  /*
 120 @@ -195,7 +195,7 @@ static void zstd_cleanup_workspace_manag
 121         struct workspace *workspace;
 122         int i;
 123
 124 -       spin_lock(&wsm.lock);
 125 +       spin_lock_bh(&wsm.lock);
 126         for (i = 0; i < ZSTD_BTRFS_MAX_LEVEL; i++) {
 127                 while (!list_empty(&wsm.idle_ws[i])) {
 128                         workspace = container_of(wsm.idle_ws[i].next,
 129 @@ -205,7 +205,7 @@ static void zstd_cleanup_workspace_manag
 130                         wsm.ops->free_workspace(&workspace->list);
 131                 }
 132         }
 133 -       spin_unlock(&wsm.lock);
 134 +       spin_unlock_bh(&wsm.lock);
 135
 136         del_timer_sync(&wsm.timer);
 137  }
 138 @@ -227,7 +227,7 @@ static struct list_head *zstd_find_works
 139         struct workspace *workspace;
 140         int i = level - 1;
 141
 142 -       spin_lock(&wsm.lock);
 143 +       spin_lock_bh(&wsm.lock);
 144         for_each_set_bit_from(i, &wsm.active_map, ZSTD_BTRFS_MAX_LEVEL) {
 145                 if (!list_empty(&wsm.idle_ws[i])) {
 146                         ws = wsm.idle_ws[i].next;
 147 @@ -239,11 +239,11 @@ static struct list_head *zstd_find_works
 148                                 list_del(&workspace->lru_list);
 149                         if (list_empty(&wsm.idle_ws[i]))
 150                                 clear_bit(i, &wsm.active_map);
 151 -                       spin_unlock(&wsm.lock);
 152 +                       spin_unlock_bh(&wsm.lock);
 153                         return ws;
 154                 }
 155         }
 156 -       spin_unlock(&wsm.lock);
 157 +       spin_unlock_bh(&wsm.lock);
 158
 159         return NULL;
 160  }
 161 @@ -302,7 +302,7 @@ static void zstd_put_workspace(struct li
 162  {
 163         struct workspace *workspace = list_to_workspace(ws);
 164
 165 -       spin_lock(&wsm.lock);
 166 +       spin_lock_bh(&wsm.lock);
 167
 168         /* A node is only taken off the lru if we are the corresponding level */
 169         if (workspace->req_level == workspace->level) {
 170 @@ -322,7 +322,7 @@ static void zstd_put_workspace(struct li
 171         list_add(&workspace->list, &wsm.idle_ws[workspace->level - 1]);
 172         workspace->req_level = 0;
 173
 174 -       spin_unlock(&wsm.lock);
 175 +       spin_unlock_bh(&wsm.lock);
 176
 177         if (workspace->level == ZSTD_BTRFS_MAX_LEVEL)
 178                 cond_wake_up(&wsm.wait);