linux-kernel - Re: [PATCH] mm/hmm: remove redundant check non_swap

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Date:   Fri, 12 Jun 2020 12:35:24 -0700
From:   Matthew Wilcox <willy@...radead.org>
To:     Ralph Campbell <rcampbell@...dia.com>
Cc:     linux-mm@...ck.org, linux-kernel@...r.kernel.org,
        Jerome Glisse <jglisse@...hat.com>,
        John Hubbard <jhubbard@...dia.com>,
        Christoph Hellwig <hch@....de>,
        Jason Gunthorpe <jgg@...lanox.com>,
        Andrew Morton <akpm@...ux-foundation.org>
Subject: Re: [PATCH] mm/hmm: remove redundant check non_swap_entry()

On Fri, Jun 12, 2020 at 12:26:18PM -0700, Ralph Campbell wrote:
> In zap_pte_range(), the check for non_swap_entry() and
> is_device_private_entry() is redundant since the latter is a subset of the
> former. Remove the redundant check to simplify the code and for clarity.

That is highly configuration dependent.

#else /* CONFIG_DEVICE_PRIVATE */
...
static inline bool is_device_private_entry(swp_entry_t entry)
{
        return false;
}

...
#if defined(CONFIG_MEMORY_FAILURE) || defined(CONFIG_MIGRATION) || \
    defined(CONFIG_DEVICE_PRIVATE)
static inline int non_swap_entry(swp_entry_t entry)
{
        return swp_type(entry) >= MAX_SWAPFILES;
}
#else
static inline int non_swap_entry(swp_entry_t entry)
{
        return 0;
}
#endif