When CACHE_SET_IO_DISABLE is set on cache set flags, bcache allocator
thread routine bch_allocator_thread() may stop the while-loops and
exit. Then it is possible to observe the following kernel oops message,
[ 631.068366] bcache: bch_btree_insert() error -5
[ 631.069115] bcache: cached_dev_detach_finish() Caching disabled for sdf
[ 631.070220] BUG: unable to handle kernel NULL pointer dereference at 0000000000000000
[ 631.070250] PGD 0 P4D 0
[ 631.070261] Oops: 0002 [#1] SMP PTI
[snipped]
[ 631.070578] Workqueue: events cache_set_flush [bcache]
[ 631.070597] RIP: 0010:exit_creds+0x1b/0x50
[ 631.070610] RSP: 0018:ffffc9000705fe08 EFLAGS: 00010246
[ 631.070626] RAX: 0000000000000001 RBX: ffff880a622ad300 RCX: 000000000000000b
[ 631.070645] RDX: 0000000000000601 RSI: 000000000000000c RDI: 0000000000000000
[ 631.070663] RBP: ffff880a622ad300 R08: ffffea00190c66e0 R09: 0000000000000200
[ 631.070682] R10: ffff880a48123000 R11: ffff880000000000 R12: 0000000000000000
[ 631.070700] R13: ffff880a4b160e40 R14: ffff880a4b160000 R15: 0ffff880667e2530
[ 631.070719] FS: 0000000000000000(0000) GS:ffff880667e00000(0000) knlGS:0000000000000000
[ 631.070740] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
[ 631.070755] CR2: 0000000000000000 CR3: 000000000200a001 CR4: 00000000003606e0
[ 631.070774] DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
[ 631.070793] DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
[ 631.070811] Call Trace:
[ 631.070828] __put_task_struct+0x55/0x160
[ 631.070845] kthread_stop+0xee/0x100
[ 631.070863] cache_set_flush+0x11d/0x1a0 [bcache]
[ 631.070879] process_one_work+0x146/0x340
[ 631.070892] worker_thread+0x47/0x3e0
[ 631.070906] kthread+0xf5/0x130
[ 631.070917] ? max_active_store+0x60/0x60
[ 631.070930] ? kthread_bind+0x10/0x10
[ 631.070945] ret_from_fork+0x35/0x40
[snipped]
[ 631.071017] RIP: exit_creds+0x1b/0x50 RSP: ffffc9000705fe08
[ 631.071033] CR2: 0000000000000000
[ 631.071045] ---[ end trace 011c63a24b22c927 ]---
[ 631.071085] bcache: bcache_device_free() bcache0 stopped
The reason is when cache_set_flush() tries to call kthread_stop() to stop
allocator thread, but it exits already due to cache device I/O errors.
This patch adds wait_for_kthread_stop() at tail of bch_allocator_thread(),
to prevent the thread routine exiting directly. Then the allocator thread
can be blocked at wait_for_kthread_stop() and wait for cache_set_flush()
to stop it by calling kthread_stop().
changelog:
v2: not directly return from allocator_wait(), move 'return 0' to tail of
bch_allocator_thread().
v1: initial version.
Fixes: 771f393e8ffc ("bcache: add CACHE_SET_IO_DISABLE to struct cache_set flags")
Signed-off-by: Coly Li <colyli@xxxxxxx>
---
drivers/md/bcache/alloc.c | 5 ++++-
1 file changed, 4 insertions(+), 1 deletion(-)
diff --git a/drivers/md/bcache/alloc.c b/drivers/md/bcache/alloc.c
index 004cc3cc6123..7fa2631b422c 100644
--- a/drivers/md/bcache/alloc.c
+++ b/drivers/md/bcache/alloc.c
@@ -290,7 +290,7 @@ do { \
if (kthread_should_stop() || \
test_bit(CACHE_SET_IO_DISABLE, &ca->set->flags)) { \
set_current_state(TASK_RUNNING); \
- return 0; \
+ goto out; \
} \
\
schedule(); \
@@ -378,6 +378,9 @@ static int bch_allocator_thread(void *arg)
bch_prio_write(ca);
}
}
+out:
+ wait_for_kthread_stop();
+ return 0;
}
/* Allocation */
--
2.16.3
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