linux-kernel - Re: [PATCH] hugetlbfs: Take read_lock on i

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Message-ID: <20191107194225.GE11823@bombadil.infradead.org>
Date:   Thu, 7 Nov 2019 11:42:25 -0800
From:   Matthew Wilcox <willy@...radead.org>
To:     Waiman Long <longman@...hat.com>
Cc:     Mike Kravetz <mike.kravetz@...cle.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        linux-kernel@...r.kernel.org, linux-mm@...ck.org,
        Davidlohr Bueso <dave@...olabs.net>,
        Peter Zijlstra <peterz@...radead.org>,
        Ingo Molnar <mingo@...hat.com>,
        Will Deacon <will.deacon@....com>
Subject: Re: [PATCH] hugetlbfs: Take read_lock on i_mmap for PMD sharing

On Thu, Nov 07, 2019 at 02:06:28PM -0500, Waiman Long wrote:
> -	i_mmap_lock_write(mapping);
> +	/*
> +	 * PMD sharing does not require changes to i_mmap. So a read lock
> +	 * is enuogh.
> +	 */
> +	i_mmap_lock_read(mapping);

We don't have comments before any of the other calls to i_mmap_lock_read()
justifying why we don't need the write lock.  I don't understand why this
situation is different.  Just delete the comment and make this a two-line
patch.