LOCKDEP warning due to ext_devt_lock

From: NeilBrown
Date: Wed May 27 2015 - 22:32:56 EST



Hi Keith,
I'm getting lockdep warning around use of ext_devt_lock.

[11428.266019] inconsistent {SOFTIRQ-ON-W} -> {IN-SOFTIRQ-W} usage.

As you say in
2da78092dda1 ("block: Fix dev_t minor allocation lifetime")
ext_devt_lock can be taken from call_rcu's soft-irq.
I think that means it should always use the _irq verion of spinlock.

I've been using the following patch and the LOCKDEP message are gone.

If you agree, could you forward it or something similar upstream?
Thanks,
NeilBrown


Signed-off-by: NeilBrown <neilb@xxxxxxx>
diff --git a/block/genhd.c b/block/genhd.c
index 666e11b83983..d1338934562e 100644
--- a/block/genhd.c
+++ b/block/genhd.c
@@ -422,9 +422,9 @@ int blk_alloc_devt(struct hd_struct *part, dev_t *devt)
/* allocate ext devt */
idr_preload(GFP_KERNEL);

- spin_lock(&ext_devt_lock);
+ spin_lock_irq(&ext_devt_lock);
idx = idr_alloc(&ext_devt_idr, part, 0, NR_EXT_DEVT, GFP_NOWAIT);
- spin_unlock(&ext_devt_lock);
+ spin_unlock_irq(&ext_devt_lock);

idr_preload_end();
if (idx < 0)
@@ -449,9 +449,9 @@ void blk_free_devt(dev_t devt)
return;

if (MAJOR(devt) == BLOCK_EXT_MAJOR) {
- spin_lock(&ext_devt_lock);
+ spin_lock_irq(&ext_devt_lock);
idr_remove(&ext_devt_idr, blk_mangle_minor(MINOR(devt)));
- spin_unlock(&ext_devt_lock);
+ spin_unlock_irq(&ext_devt_lock);
}
}

@@ -690,13 +690,13 @@ struct gendisk *get_gendisk(dev_t devt, int *partno)
} else {
struct hd_struct *part;

- spin_lock(&ext_devt_lock);
+ spin_lock_irq(&ext_devt_lock);
part = idr_find(&ext_devt_idr, blk_mangle_minor(MINOR(devt)));
if (part && get_disk(part_to_disk(part))) {
*partno = part->partno;
disk = part_to_disk(part);
}
- spin_unlock(&ext_devt_lock);
+ spin_unlock_irq(&ext_devt_lock);
}

return disk;

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