linux-kernel - Re: [PATCH v2 3/5] mm/hugeltb: clarify (chg - freed) won't go negative in hugetlb_unreserve

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Message-ID: <23a4924a-2881-3c5e-b70e-ece65a0cb7ca@oracle.com>
Date:   Mon, 12 Apr 2021 11:28:41 -0700
From:   Mike Kravetz <mike.kravetz@...cle.com>
To:     Miaohe Lin <linmiaohe@...wei.com>, akpm@...ux-foundation.org
Cc:     linux-kernel@...r.kernel.org, linux-mm@...ck.org,
        linfeilong@...wei.com
Subject: Re: [PATCH v2 3/5] mm/hugeltb: clarify (chg - freed) won't go
 negative in hugetlb_unreserve_pages()

On 4/10/21 12:23 AM, Miaohe Lin wrote:
> The resv_map could be NULL since this routine can be called in the evict
> inode path for all hugetlbfs inodes and we will have chg = 0 in this case.
> But (chg - freed) won't go negative as Mike pointed out:
> 
>  "If resv_map is NULL, then no hugetlb pages can be allocated/associated
>   with the file.  As a result, remove_inode_hugepages will never find any
>   huge pages associated with the inode and the passed value 'freed' will
>   always be zero."
> 
> Add a comment clarifying this to make it clear and also avoid confusion.
> 
> Signed-off-by: Miaohe Lin <linmiaohe@...wei.com>

Thanks,

Reviewed-by: Mike Kravetz <mike.kravetz@...cle.com>
-- 
Mike Kravetz