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Date: Tue, 19 Jun 2018 07:05:57 -0700
From: Matthew Wilcox <willy@infradead.org>
Subject: Re: [bug report] mm: Convert collapse_shmem to XArray
Message-ID: <20180619140557.GB1438@bombadil.infradead.org>
References: <20180619112944.f2fokthjunzavgcw@kili.mountain>
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To: Dan Carpenter <dan.carpenter@oracle.com>
Cc: linux-mm@kvack.org

On Tue, Jun 19, 2018 at 02:29:44PM +0300, Dan Carpenter wrote:
> Hello Matthew Wilcox,
> 
> The patch d31429cb560d: "mm: Convert collapse_shmem to XArray" from
> Dec 4, 2017, leads to the following static checker warning:
> 
> 	mm/khugepaged.c:1435 collapse_shmem()
> 	error: double unlock 'irq:'
> 
> mm/khugepaged.c
>   1398                  xas_unlock_irq(&xas);
>   1399  
>   1400                  if (isolate_lru_page(page)) {
>   1401                          result = SCAN_DEL_PAGE_LRU;
>   1402                          goto out_isolate_failed;
>   1403                  }
>   1404  
>   1405                  if (page_mapped(page))
>   1406                          unmap_mapping_pages(mapping, index, 1, false);
>   1407  
>   1408                  xas_lock(&xas);
>                         ^^^^^^^^^^^^^^
> This used to disable IRQs.

*headdesk*.  Thanks, fix pushed.

>   1434  out_lru:
>   1435                  xas_unlock_irq(&xas);
>                         ^^^^^^^^^^^^^^^^^^^
> So I guess we should change this to xas_unlock(&xas);?

Nah, other way around.  No idea why I had xas_lock() there instead of
xas_lock_irq().