sbitmap: silence bogus lockdep IRQ warning

Ming reports that lockdep spews the following trace. What this
essentially says is that the sbitmap swap_lock was used inconsistently
in IRQ enabled and disabled context, and that is usually indicative of a
bug that will cause a deadlock.

For this case, it's a false positive. The swap_lock is used from process
context only, when we swap the bits in the word and cleared mask. We
also end up doing that when we are getting a driver tag, from the
blk_mq_mark_tag_wait(), and from there we hold the waitqueue lock with
IRQs disabled. However, this isn't from an actual IRQ, it's still
process context.

In lieu of a better way to fix this, simply always disable interrupts
when grabbing the swap_lock if lockdep is enabled.

[  100.967642] ================start test sanity/001================
[  101.238280] null: module loaded
[  106.093735]
[  106.094012] =====================================================
[  106.094854] WARNING: SOFTIRQ-safe -> SOFTIRQ-unsafe lock order detected
[  106.095759] 4.20.0-rc3_5d2ee7122c73_for-next+ #1 Not tainted
[  106.096551] -----------------------------------------------------
[  106.097386] fio/1043 [HC0[0]:SC0[0]:HE0:SE1] is trying to acquire:
[  106.098231] 000000004c43fa71
(&(&sb->map[i].swap_lock)->rlock){+.+.}, at: sbitmap_get+0xd5/0x22c
[  106.099431]
[  106.099431] and this task is already holding:
[  106.100229] 000000007eec8b2f
(&(&hctx->dispatch_wait_lock)->rlock){....}, at:
blk_mq_dispatch_rq_list+0x4c1/0xd7c
[  106.101630] which would create a new lock dependency:
[  106.102326]  (&(&hctx->dispatch_wait_lock)->rlock){....} ->
(&(&sb->map[i].swap_lock)->rlock){+.+.}
[  106.103553]
[  106.103553] but this new dependency connects a SOFTIRQ-irq-safe lock:
[  106.104580]  (&sbq->ws[i].wait){..-.}
[  106.104582]
[  106.104582] ... which became SOFTIRQ-irq-safe at:
[  106.105751]   _raw_spin_lock_irqsave+0x4b/0x82
[  106.106284]   __wake_up_common_lock+0x119/0x1b9
[  106.106825]   sbitmap_queue_wake_up+0x33f/0x383
[  106.107456]   sbitmap_queue_clear+0x4c/0x9a
[  106.108046]   __blk_mq_free_request+0x188/0x1d3
[  106.108581]   blk_mq_free_request+0x23b/0x26b
[  106.109102]   scsi_end_request+0x345/0x5d7
[  106.109587]   scsi_io_completion+0x4b5/0x8f0
[  106.110099]   scsi_finish_command+0x412/0x456
[  106.110615]   scsi_softirq_done+0x23f/0x29b
[  106.111115]   blk_done_softirq+0x2a7/0x2e6
[  106.111608]   __do_softirq+0x360/0x6ad
[  106.112062]   run_ksoftirqd+0x2f/0x5b
[  106.112499]   smpboot_thread_fn+0x3a5/0x3db
[  106.113000]   kthread+0x1d4/0x1e4
[  106.113457]   ret_from_fork+0x3a/0x50
[  106.113969]
[  106.113969] to a SOFTIRQ-irq-unsafe lock:
[  106.114672]  (&(&sb->map[i].swap_lock)->rlock){+.+.}
[  106.114674]
[  106.114674] ... which became SOFTIRQ-irq-unsafe at:
[  106.116000] ...
[  106.116003]   _raw_spin_lock+0x33/0x64
[  106.116676]   sbitmap_get+0xd5/0x22c
[  106.117134]   __sbitmap_queue_get+0xe8/0x177
[  106.117731]   __blk_mq_get_tag+0x1e6/0x22d
[  106.118286]   blk_mq_get_tag+0x1db/0x6e4
[  106.118756]   blk_mq_get_driver_tag+0x161/0x258
[  106.119383]   blk_mq_dispatch_rq_list+0x28e/0xd7c
[  106.120043]   blk_mq_do_dispatch_sched+0x23a/0x287
[  106.120607]   blk_mq_sched_dispatch_requests+0x379/0x3fc
[  106.121234]   __blk_mq_run_hw_queue+0x137/0x17e
[  106.121781]   __blk_mq_delay_run_hw_queue+0x80/0x25f
[  106.122366]   blk_mq_run_hw_queue+0x151/0x187
[  106.122887]   blk_mq_sched_insert_requests+0x13f/0x175
[  106.123492]   blk_mq_flush_plug_list+0x7d6/0x81b
[  106.124042]   blk_flush_plug_list+0x392/0x3d7
[  106.124557]   blk_finish_plug+0x37/0x4f
[  106.125019]   read_pages+0x3ef/0x430
[  106.125446]   __do_page_cache_readahead+0x18e/0x2fc
[  106.126027]   force_page_cache_readahead+0x121/0x133
[  106.126621]   page_cache_sync_readahead+0x35f/0x3bb
[  106.127229]   generic_file_buffered_read+0x410/0x1860
[  106.127932]   __vfs_read+0x319/0x38f
[  106.128415]   vfs_read+0xd2/0x19a
[  106.128817]   ksys_read+0xb9/0x135
[  106.129225]   do_syscall_64+0x140/0x385
[  106.129684]   entry_SYSCALL_64_after_hwframe+0x49/0xbe
[  106.130292]
[  106.130292] other info that might help us debug this:
[  106.130292]
[  106.131226] Chain exists of:
[  106.131226]   &sbq->ws[i].wait -->
&(&hctx->dispatch_wait_lock)->rlock -->
&(&sb->map[i].swap_lock)->rlock
[  106.131226]
[  106.132865]  Possible interrupt unsafe locking scenario:
[  106.132865]
[  106.133659]        CPU0                    CPU1
[  106.134194]        ----                    ----
[  106.134733]   lock(&(&sb->map[i].swap_lock)->rlock);
[  106.135318]                                local_irq_disable();
[  106.136014]                                lock(&sbq->ws[i].wait);
[  106.136747]
lock(&(&hctx->dispatch_wait_lock)->rlock);
[  106.137742]   <Interrupt>
[  106.138110]     lock(&sbq->ws[i].wait);
[  106.138625]
[  106.138625]  *** DEADLOCK ***
[  106.138625]
[  106.139430] 3 locks held by fio/1043:
[  106.139947]  #0: 0000000076ff0fd9 (rcu_read_lock){....}, at:
hctx_lock+0x29/0xe8
[  106.140813]  #1: 000000002feb1016 (&sbq->ws[i].wait){..-.}, at:
blk_mq_dispatch_rq_list+0x4ad/0xd7c
[  106.141877]  #2: 000000007eec8b2f
(&(&hctx->dispatch_wait_lock)->rlock){....}, at:
blk_mq_dispatch_rq_list+0x4c1/0xd7c
[  106.143267]
[  106.143267] the dependencies between SOFTIRQ-irq-safe lock and the
holding lock:
[  106.144351]  -> (&sbq->ws[i].wait){..-.} ops: 82 {
[  106.144926]     IN-SOFTIRQ-W at:
[  106.145314]                       _raw_spin_lock_irqsave+0x4b/0x82
[  106.146042]                       __wake_up_common_lock+0x119/0x1b9
[  106.146785]                       sbitmap_queue_wake_up+0x33f/0x383
[  106.147567]                       sbitmap_queue_clear+0x4c/0x9a
[  106.148379]                       __blk_mq_free_request+0x188/0x1d3
[  106.149148]                       blk_mq_free_request+0x23b/0x26b
[  106.149864]                       scsi_end_request+0x345/0x5d7
[  106.150546]                       scsi_io_completion+0x4b5/0x8f0
[  106.151367]                       scsi_finish_command+0x412/0x456
[  106.152157]                       scsi_softirq_done+0x23f/0x29b
[  106.152855]                       blk_done_softirq+0x2a7/0x2e6
[  106.153537]                       __do_softirq+0x360/0x6ad
[  106.154280]                       run_ksoftirqd+0x2f/0x5b
[  106.155020]                       smpboot_thread_fn+0x3a5/0x3db
[  106.155828]                       kthread+0x1d4/0x1e4
[  106.156526]                       ret_from_fork+0x3a/0x50
[  106.157267]     INITIAL USE at:
[  106.157713]                      _raw_spin_lock_irqsave+0x4b/0x82
[  106.158542]                      prepare_to_wait_exclusive+0xa8/0x215
[  106.159421]                      blk_mq_get_tag+0x34f/0x6e4
[  106.160186]                      blk_mq_get_request+0x48e/0xaef
[  106.160997]                      blk_mq_make_request+0x27e/0xbd2
[  106.161828]                      generic_make_request+0x4d1/0x873
[  106.162661]                      submit_bio+0x20c/0x253
[  106.163379]                      mpage_bio_submit+0x44/0x4b
[  106.164142]                      mpage_readpages+0x3c2/0x407
[  106.164919]                      read_pages+0x13a/0x430
[  106.165633]                      __do_page_cache_readahead+0x18e/0x2fc
[  106.166530]                      force_page_cache_readahead+0x121/0x133
[  106.167439]                      page_cache_sync_readahead+0x35f/0x3bb
[  106.168337]                      generic_file_buffered_read+0x410/0x1860
[  106.169255]                      __vfs_read+0x319/0x38f
[  106.169977]                      vfs_read+0xd2/0x19a
[  106.170662]                      ksys_read+0xb9/0x135
[  106.171356]                      do_syscall_64+0x140/0x385
[  106.172120]                      entry_SYSCALL_64_after_hwframe+0x49/0xbe
[  106.173051]   }
[  106.173308]   ... key      at: [<ffffffff85094600>] __key.26481+0x0/0x40
[  106.174219]   ... acquired at:
[  106.174646]    _raw_spin_lock+0x33/0x64
[  106.175183]    blk_mq_dispatch_rq_list+0x4c1/0xd7c
[  106.175843]    blk_mq_do_dispatch_sched+0x23a/0x287
[  106.176518]    blk_mq_sched_dispatch_requests+0x379/0x3fc
[  106.177262]    __blk_mq_run_hw_queue+0x137/0x17e
[  106.177900]    __blk_mq_delay_run_hw_queue+0x80/0x25f
[  106.178591]    blk_mq_run_hw_queue+0x151/0x187
[  106.179207]    blk_mq_sched_insert_requests+0x13f/0x175
[  106.179926]    blk_mq_flush_plug_list+0x7d6/0x81b
[  106.180571]    blk_flush_plug_list+0x392/0x3d7
[  106.181187]    blk_finish_plug+0x37/0x4f
[  106.181737]    __se_sys_io_submit+0x171/0x304
[  106.182346]    do_syscall_64+0x140/0x385
[  106.182895]    entry_SYSCALL_64_after_hwframe+0x49/0xbe
[  106.183607]
[  106.183830] -> (&(&hctx->dispatch_wait_lock)->rlock){....} ops: 1 {
[  106.184691]    INITIAL USE at:
[  106.185119]                    _raw_spin_lock+0x33/0x64
[  106.185838]                    blk_mq_dispatch_rq_list+0x4c1/0xd7c
[  106.186697]                    blk_mq_do_dispatch_sched+0x23a/0x287
[  106.187551]                    blk_mq_sched_dispatch_requests+0x379/0x3fc
[  106.188481]                    __blk_mq_run_hw_queue+0x137/0x17e
[  106.189307]                    __blk_mq_delay_run_hw_queue+0x80/0x25f
[  106.190189]                    blk_mq_run_hw_queue+0x151/0x187
[  106.190989]                    blk_mq_sched_insert_requests+0x13f/0x175
[  106.191902]                    blk_mq_flush_plug_list+0x7d6/0x81b
[  106.192739]                    blk_flush_plug_list+0x392/0x3d7
[  106.193535]                    blk_finish_plug+0x37/0x4f
[  106.194269]                    __se_sys_io_submit+0x171/0x304
[  106.195059]                    do_syscall_64+0x140/0x385
[  106.195794]                    entry_SYSCALL_64_after_hwframe+0x49/0xbe
[  106.196705]  }
[  106.196950]  ... key      at: [<ffffffff84880620>] __key.51231+0x0/0x40
[  106.197853]  ... acquired at:
[  106.198270]    lock_acquire+0x280/0x2f3
[  106.198806]    _raw_spin_lock+0x33/0x64
[  106.199337]    sbitmap_get+0xd5/0x22c
[  106.199850]    __sbitmap_queue_get+0xe8/0x177
[  106.200450]    __blk_mq_get_tag+0x1e6/0x22d
[  106.201035]    blk_mq_get_tag+0x1db/0x6e4
[  106.201589]    blk_mq_get_driver_tag+0x161/0x258
[  106.202237]    blk_mq_dispatch_rq_list+0x5b9/0xd7c
[  106.202902]    blk_mq_do_dispatch_sched+0x23a/0x287
[  106.203572]    blk_mq_sched_dispatch_requests+0x379/0x3fc
[  106.204316]    __blk_mq_run_hw_queue+0x137/0x17e
[  106.204956]    __blk_mq_delay_run_hw_queue+0x80/0x25f
[  106.205649]    blk_mq_run_hw_queue+0x151/0x187
[  106.206269]    blk_mq_sched_insert_requests+0x13f/0x175
[  106.206997]    blk_mq_flush_plug_list+0x7d6/0x81b
[  106.207644]    blk_flush_plug_list+0x392/0x3d7
[  106.208264]    blk_finish_plug+0x37/0x4f
[  106.208814]    __se_sys_io_submit+0x171/0x304
[  106.209415]    do_syscall_64+0x140/0x385
[  106.209965]    entry_SYSCALL_64_after_hwframe+0x49/0xbe
[  106.210684]
[  106.210904]
[  106.210904] the dependencies between the lock to be acquired
[  106.210905]  and SOFTIRQ-irq-unsafe lock:
[  106.212541] -> (&(&sb->map[i].swap_lock)->rlock){+.+.} ops: 1969 {
[  106.213393]    HARDIRQ-ON-W at:
[  106.213840]                     _raw_spin_lock+0x33/0x64
[  106.214570]                     sbitmap_get+0xd5/0x22c
[  106.215282]                     __sbitmap_queue_get+0xe8/0x177
[  106.216086]                     __blk_mq_get_tag+0x1e6/0x22d
[  106.216876]                     blk_mq_get_tag+0x1db/0x6e4
[  106.217627]                     blk_mq_get_driver_tag+0x161/0x258
[  106.218465]                     blk_mq_dispatch_rq_list+0x28e/0xd7c
[  106.219326]                     blk_mq_do_dispatch_sched+0x23a/0x287
[  106.220198]                     blk_mq_sched_dispatch_requests+0x379/0x3fc
[  106.221138]                     __blk_mq_run_hw_queue+0x137/0x17e
[  106.221975]                     __blk_mq_delay_run_hw_queue+0x80/0x25f
[  106.222874]                     blk_mq_run_hw_queue+0x151/0x187
[  106.223686]                     blk_mq_sched_insert_requests+0x13f/0x175
[  106.224597]                     blk_mq_flush_plug_list+0x7d6/0x81b
[  106.225444]                     blk_flush_plug_list+0x392/0x3d7
[  106.226255]                     blk_finish_plug+0x37/0x4f
[  106.227006]                     read_pages+0x3ef/0x430
[  106.227717]                     __do_page_cache_readahead+0x18e/0x2fc
[  106.228595]                     force_page_cache_readahead+0x121/0x133
[  106.229491]                     page_cache_sync_readahead+0x35f/0x3bb
[  106.230373]                     generic_file_buffered_read+0x410/0x1860
[  106.231277]                     __vfs_read+0x319/0x38f
[  106.231986]                     vfs_read+0xd2/0x19a
[  106.232666]                     ksys_read+0xb9/0x135
[  106.233350]                     do_syscall_64+0x140/0x385
[  106.234097]                     entry_SYSCALL_64_after_hwframe+0x49/0xbe
[  106.235012]    SOFTIRQ-ON-W at:
[  106.235460]                     _raw_spin_lock+0x33/0x64
[  106.236195]                     sbitmap_get+0xd5/0x22c
[  106.236913]                     __sbitmap_queue_get+0xe8/0x177
[  106.237715]                     __blk_mq_get_tag+0x1e6/0x22d
[  106.238488]                     blk_mq_get_tag+0x1db/0x6e4
[  106.239244]                     blk_mq_get_driver_tag+0x161/0x258
[  106.240079]                     blk_mq_dispatch_rq_list+0x28e/0xd7c
[  106.240937]                     blk_mq_do_dispatch_sched+0x23a/0x287
[  106.241806]                     blk_mq_sched_dispatch_requests+0x379/0x3fc
[  106.242751]                     __blk_mq_run_hw_queue+0x137/0x17e
[  106.243579]                     __blk_mq_delay_run_hw_queue+0x80/0x25f
[  106.244469]                     blk_mq_run_hw_queue+0x151/0x187
[  106.245277]                     blk_mq_sched_insert_requests+0x13f/0x175
[  106.246191]                     blk_mq_flush_plug_list+0x7d6/0x81b
[  106.247044]                     blk_flush_plug_list+0x392/0x3d7
[  106.247859]                     blk_finish_plug+0x37/0x4f
[  106.248749]                     read_pages+0x3ef/0x430
[  106.249463]                     __do_page_cache_readahead+0x18e/0x2fc
[  106.250357]                     force_page_cache_readahead+0x121/0x133
[  106.251263]                     page_cache_sync_readahead+0x35f/0x3bb
[  106.252157]                     generic_file_buffered_read+0x410/0x1860
[  106.253084]                     __vfs_read+0x319/0x38f
[  106.253808]                     vfs_read+0xd2/0x19a
[  106.254488]                     ksys_read+0xb9/0x135
[  106.255186]                     do_syscall_64+0x140/0x385
[  106.255943]                     entry_SYSCALL_64_after_hwframe+0x49/0xbe
[  106.256867]    INITIAL USE at:
[  106.257300]                    _raw_spin_lock+0x33/0x64
[  106.258033]                    sbitmap_get+0xd5/0x22c
[  106.258747]                    __sbitmap_queue_get+0xe8/0x177
[  106.259542]                    __blk_mq_get_tag+0x1e6/0x22d
[  106.260320]                    blk_mq_get_tag+0x1db/0x6e4
[  106.261072]                    blk_mq_get_driver_tag+0x161/0x258
[  106.261902]                    blk_mq_dispatch_rq_list+0x28e/0xd7c
[  106.262762]                    blk_mq_do_dispatch_sched+0x23a/0x287
[  106.263626]                    blk_mq_sched_dispatch_requests+0x379/0x3fc
[  106.264571]                    __blk_mq_run_hw_queue+0x137/0x17e
[  106.265409]                    __blk_mq_delay_run_hw_queue+0x80/0x25f
[  106.266302]                    blk_mq_run_hw_queue+0x151/0x187
[  106.267111]                    blk_mq_sched_insert_requests+0x13f/0x175
[  106.268028]                    blk_mq_flush_plug_list+0x7d6/0x81b
[  106.268878]                    blk_flush_plug_list+0x392/0x3d7
[  106.269694]                    blk_finish_plug+0x37/0x4f
[  106.270432]                    read_pages+0x3ef/0x430
[  106.271139]                    __do_page_cache_readahead+0x18e/0x2fc
[  106.272040]                    force_page_cache_readahead+0x121/0x133
[  106.272932]                    page_cache_sync_readahead+0x35f/0x3bb
[  106.273811]                    generic_file_buffered_read+0x410/0x1860
[  106.274709]                    __vfs_read+0x319/0x38f
[  106.275407]                    vfs_read+0xd2/0x19a
[  106.276074]                    ksys_read+0xb9/0x135
[  106.276764]                    do_syscall_64+0x140/0x385
[  106.277500]                    entry_SYSCALL_64_after_hwframe+0x49/0xbe
[  106.278417]  }
[  106.278676]  ... key      at: [<ffffffff85094640>] __key.26212+0x0/0x40
[  106.279586]  ... acquired at:
[  106.280026]    lock_acquire+0x280/0x2f3
[  106.280559]    _raw_spin_lock+0x33/0x64
[  106.281101]    sbitmap_get+0xd5/0x22c
[  106.281610]    __sbitmap_queue_get+0xe8/0x177
[  106.282221]    __blk_mq_get_tag+0x1e6/0x22d
[  106.282809]    blk_mq_get_tag+0x1db/0x6e4
[  106.283368]    blk_mq_get_driver_tag+0x161/0x258
[  106.284018]    blk_mq_dispatch_rq_list+0x5b9/0xd7c
[  106.284685]    blk_mq_do_dispatch_sched+0x23a/0x287
[  106.285371]    blk_mq_sched_dispatch_requests+0x379/0x3fc
[  106.286135]    __blk_mq_run_hw_queue+0x137/0x17e
[  106.286806]    __blk_mq_delay_run_hw_queue+0x80/0x25f
[  106.287515]    blk_mq_run_hw_queue+0x151/0x187
[  106.288149]    blk_mq_sched_insert_requests+0x13f/0x175
[  106.289041]    blk_mq_flush_plug_list+0x7d6/0x81b
[  106.289912]    blk_flush_plug_list+0x392/0x3d7
[  106.290590]    blk_finish_plug+0x37/0x4f
[  106.291238]    __se_sys_io_submit+0x171/0x304
[  106.291864]    do_syscall_64+0x140/0x385
[  106.292534]    entry_SYSCALL_64_after_hwframe+0x49/0xbe

Reported-by: Ming Lei <ming.lei@redhat.com>
Tested-by: Guenter Roeck <linux@roeck-us.net>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

1 files changed, 8 insertions, 0 deletions

diff --git a/lib/sbitmap.c b/lib/sbitmap.c
index a89fbe7cf6ca..2261136ae067 100644
--- a/lib/sbitmap.c
+++ b/lib/sbitmap.c
@@ -118,8 +118,13 @@ static int __sbitmap_get_word(unsigned long *word, unsigned long depth,
 static inline bool sbitmap_deferred_clear(struct sbitmap *sb, int index)
 {
 	unsigned long mask, val;
+	unsigned long __maybe_unused flags;
 	bool ret = false;
 
+	/* Silence bogus lockdep warning */
+#if defined(CONFIG_LOCKDEP)
+	local_irq_save(flags);
+#endif
 	spin_lock(&sb->map[index].swap_lock);
 
 	if (!sb->map[index].cleared)
@@ -142,6 +147,9 @@ static inline bool sbitmap_deferred_clear(struct sbitmap *sb, int index)
 	ret = true;
 out_unlock:
 	spin_unlock(&sb->map[index].swap_lock);
+#if defined(CONFIG_LOCKDEP)
+	local_irq_restore(flags);
+#endif
 	return ret;
 }