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Date:   Tue, 13 Nov 2018 05:32:43 -0800
From:   Matthew Wilcox <willy@infradead.org>
To:     Wei Yang <richard.weiyang@gmail.com>
Cc:     akpm@linux-foundation.org, mgorman@techsingularity.net,
        linux-mm@kvack.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH v2] vmscan: return NODE_RECLAIM_NOSCAN in node_reclaim()
 when CONFIG_NUMA is n
Message-ID: <20181113133243.GW21824@bombadil.infradead.org>
References: <20181113041750.20784-1-richard.weiyang@gmail.com>
 <20181113080436.22078-1-richard.weiyang@gmail.com>
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On Tue, Nov 13, 2018 at 04:04:36PM +0800, Wei Yang wrote:
> This patch fix the return value by adjusting to NODE_RECLAIM_NOSCAN. Since
> node_reclaim() is only called in page_alloc.c, move it to mm/internal.h.

linux/swap.h is included in quite a few places in the kernel, but let's
see what's really used from it outside mm/

SWAP_FLAG* -- only used in mm/swapfile.c.  Move to swapfile.c?
current_is_kswapd() -- used by some drivers.
MAX_SWAPFILES* -- used by arch code.
union swap_header -- used by mtdswap.
struct reclaim_state -- used by fs/inode.c.
struct swap_extent -- embedded in swap_info_struct, which is used widely.
struct swap_cluster_info -- ditto
struct vma_swap_readahead -- only used in swap_state.c.  Move it there?
nr_free_pages() -- used in fs/ and kernel/power/swap.c
totalram_pages -- used widely
totalreserve_pages -- used widely
vm_swappiness -- used by sysctl
vm_total_pages -- only used in mm -- move to mm/internal.h?
node_reclaim_mode -- used by sysctl
kswapd_run -- only used in mm
kswapd_stop -- ditto
swap_address_space -- only used in mm
swapper_spaces -- likewise
SWAP_ADDRESS_SPACE* --likewise

I haven't covered all of the file, but there's definitely opportunity
for some followup patches to shrink linux/swap.h.