Re: unexpected -ENOMEM from percpu_counter_init()

[Vlastimil Babka <vbabka@suse.cz>]

+CC btrfs

On 4/1/21 12:51 PM, Wang Yugui wrote:
> Hi,
> 
> an unexpected -ENOMEM from percpu_counter_init() happened when xfstest 
> with kernel 5.11.10 and 5.10.27

Is there a dmesg log showing allocation failure or something?

> direct caller:
> int btrfs_drew_lock_init(struct btrfs_drew_lock *lock)
> {
>     int ret;
> 
>     ret = percpu_counter_init(&lock->writers, 0, GFP_KERNEL);
>     if (ret)
>         return ret;
> 
>     atomic_set(&lock->readers, 0);
>     init_waitqueue_head(&lock->pending_readers);
>     init_waitqueue_head(&lock->pending_writers);
> 
>     return 0;
> }
> 
> upper caller:
>     nofs_flag = memalloc_nofs_save();
>     ret = btrfs_drew_lock_init(&root->snapshot_lock);
>     memalloc_nofs_restore(nofs_flag);
>     if (ret == -ENOMEM) printk("ENOMEM btrfs_drew_lock_init\n");
>     if (ret)
>         goto fail;
> 
> The hardware of this server:
> CPU:  Xeon(R) CPU E5-2660 v2(10 core)  *2
> memory:  192G, no swap
> 
> Only one xfstests job is running in this server, and about 7% of memory
> is used.
> 
> Any advice please.
> 
> Best Regards
> Wang Yugui (wangyugui@e16-tech.com)
> 2021/04/01
> 
>