linux-kernel - Re: [PATCH 06/10] hugetlbfs: Convert remove_inode_hugepages() to use filemap_get

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Message-ID: <6fc6e9de-39c2-3244-ef92-a1de0d390889@oracle.com>
Date:   Fri, 10 Jun 2022 14:56:05 -0700
From:   Mike Kravetz <mike.kravetz@...cle.com>
To:     Matthew Wilcox <willy@...radead.org>,
        Sumanth Korikkar <sumanthk@...ux.ibm.com>
Cc:     linux-ext4@...r.kernel.org, gerald.schaefer@...ux.ibm.com,
        gor@...ux.ibm.com, agordeev@...ux.ibm.com,
        linux-f2fs-devel@...ts.sourceforge.net,
        linux-fsdevel@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-mm@...ck.org, linux-nilfs@...r.kernel.org
Subject: Re: [PATCH 06/10] hugetlbfs: Convert remove_inode_hugepages() to use
 filemap_get_folios()

On 6/10/22 14:17, Matthew Wilcox wrote:
> On Fri, Jun 10, 2022 at 05:52:05PM +0200, Sumanth Korikkar wrote:
>> To reproduce:
>> * clone libhugetlbfs:
>> * Execute, PATH=$PATH:"obj64/" LD_LIBRARY_PATH=../obj64/ alloc-instantiate-race shared
> 
> ... it's a lot harder to set up hugetlb than that ...
> 
> anyway, i figured it out without being able to run the reproducer.
> 
> Can you try this?

I can confirm that libhugetlbfs tests do not trigger the BUG with the
below change.
-- 
Mike Kravetz

> 
> diff --git a/mm/filemap.c b/mm/filemap.c
> index a30587f2e598..8ef861297ffb 100644
> --- a/mm/filemap.c
> +++ b/mm/filemap.c
> @@ -2160,7 +2160,11 @@ unsigned filemap_get_folios(struct address_space *mapping, pgoff_t *start,
>  		if (xa_is_value(folio))
>  			continue;
>  		if (!folio_batch_add(fbatch, folio)) {
> -			*start = folio->index + folio_nr_pages(folio);
> +			unsigned long nr = folio_nr_pages(folio);
> +
> +			if (folio_test_hugetlb(folio))
> +				nr = 1;
> +			*start = folio->index + nr;
>  			goto out;
>  		}
>  	}
>