If preparing a write bio fails then blk_zone_wplug_bio_work() calls
bio_endio() with zwplug->lock held. If a device mapper driver is stacked
on top of the zoned block device then this results in nested locking of
zwplug->lock. The resulting lockdep complaint is a false positive
because this is nested locking and not recursive locking. Suppress this
false positive by calling blk_zone_wplug_bio_io_error() without holding
zwplug->lock. This is safe because no code in
blk_zone_wplug_bio_io_error() depends on zwplug->lock being held. This
patch suppresses the following lockdep complaint:
WARNING: possible recursive locking detected
--------------------------------------------
kworker/3:0H/46 is trying to acquire lock:
ffffff882968b830 (&zwplug->lock){-...}-{2:2}, at: blk_zone_write_plug_bio_endio+0x64/0x1f0
but task is already holding lock:
ffffff88315bc230 (&zwplug->lock){-...}-{2:2}, at: blk_zone_wplug_bio_work+0x8c/0x48c
other info that might help us debug this:
Possible unsafe locking scenario:
CPU0
----
lock(&zwplug->lock);
lock(&zwplug->lock);
*** DEADLOCK ***
May be due to missing lock nesting notation
3 locks held by kworker/3:0H/46:
#0: ffffff8809486758 ((wq_completion)sdd_zwplugs){+.+.}-{0:0}, at: process_one_work+0x1bc/0x65c
#1: ffffffc085de3d70 ((work_completion)(&zwplug->bio_work)){+.+.}-{0:0}, at: process_one_work+0x1e4/0x65c
#2: ffffff88315bc230 (&zwplug->lock){-...}-{2:2}, at: blk_zone_wplug_bio_work+0x8c/0x48c
stack backtrace:
CPU: 3 UID: 0 PID: 46 Comm: kworker/3:0H Tainted: G W OE 6.12.38-android16-5-maybe-dirty-4k #1 8b362b6f76e3645a58cd27d86982bce10d150025
Tainted: [W]=WARN, [O]=OOT_MODULE, [E]=UNSIGNED_MODULE
Hardware name: Spacecraft board based on MALIBU (DT)
Workqueue: sdd_zwplugs blk_zone_wplug_bio_work
Call trace:
dump_backtrace+0xfc/0x17c
show_stack+0x18/0x28
dump_stack_lvl+0x40/0xa0
dump_stack+0x18/0x24
print_deadlock_bug+0x38c/0x398
__lock_acquire+0x13e8/0x2e1c
lock_acquire+0x134/0x2b4
_raw_spin_lock_irqsave+0x5c/0x80
blk_zone_write_plug_bio_endio+0x64/0x1f0
bio_endio+0x9c/0x240
__dm_io_complete+0x214/0x260
clone_endio+0xe8/0x214
bio_endio+0x218/0x240
blk_zone_wplug_bio_work+0x204/0x48c
process_one_work+0x26c/0x65c
worker_thread+0x33c/0x498
kthread+0x110/0x134
ret_from_fork+0x10/0x20
Cc: Damien Le Moal <dlemoal@xxxxxxxxxx>
Cc: Christoph Hellwig <hch@xxxxxx>
Fixes: dd291d77cc90 ("block: Introduce zone write plugging")
Signed-off-by: Bart Van Assche <bvanassche@xxxxxxx>
---
block/blk-zoned.c | 11 ++++++-----
1 file changed, 6 insertions(+), 5 deletions(-)
diff --git a/block/blk-zoned.c b/block/blk-zoned.c
index ef43aaca49f4..5e2a5788dc3b 100644
--- a/block/blk-zoned.c
+++ b/block/blk-zoned.c
@@ -1286,14 +1286,14 @@ static void blk_zone_wplug_bio_work(struct work_struct *work)
struct block_device *bdev;
unsigned long flags;
struct bio *bio;
+ bool prepared;
/*
* Submit the next plugged BIO. If we do not have any, clear
* the plugged flag.
*/
- spin_lock_irqsave(&zwplug->lock, flags);
-
again:
+ spin_lock_irqsave(&zwplug->lock, flags);
bio = bio_list_pop(&zwplug->bio_list);
if (!bio) {
zwplug->flags &= ~BLK_ZONE_WPLUG_PLUGGED;
@@ -1304,13 +1304,14 @@ static void blk_zone_wplug_bio_work(struct work_struct *work)
trace_blk_zone_wplug_bio(zwplug->disk->queue, zwplug->zone_no,
bio->bi_iter.bi_sector, bio_sectors(bio));
- if (!blk_zone_wplug_prepare_bio(zwplug, bio)) {
+ prepared = blk_zone_wplug_prepare_bio(zwplug, bio);
+ spin_unlock_irqrestore(&zwplug->lock, flags);
+
+ if (!prepared) {
blk_zone_wplug_bio_io_error(zwplug, bio);
goto again;
}
- spin_unlock_irqrestore(&zwplug->lock, flags);
-
bdev = bio->bi_bdev;
/*
