linux-kernel - Re: [PATCH v9 3/3] mm, pmem, xfs: Introduce MF_MEM

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Date:   Sun, 5 Feb 2023 21:10:41 +0000
From:   Matthew Wilcox <willy@...radead.org>
To:     Shiyang Ruan <ruansy.fnst@...itsu.com>
Cc:     linux-kernel@...r.kernel.org, linux-xfs@...r.kernel.org,
        nvdimm@...ts.linux.dev, linux-mm@...ck.org,
        linux-fsdevel@...r.kernel.org, djwong@...nel.org,
        dan.j.williams@...el.com, david@...morbit.com, hch@...radead.org,
        jane.chu@...cle.com
Subject: Re: [PATCH v9 3/3] mm, pmem, xfs: Introduce MF_MEM_REMOVE for unbind

On Sat, Feb 04, 2023 at 02:58:38PM +0000, Shiyang Ruan wrote:
> +	if (mf_flags & MF_MEM_PRE_REMOVE) {
> +		xfs_info(mp, "device is about to be removed!");
> +		down_write(&mp->m_super->s_umount);
> +		error = sync_filesystem(mp->m_super);
> +		/* invalidate_inode_pages2() invalidates dax mapping */
> +		super_drop_pagecache(mp->m_super, invalidate_inode_pages2);

OK, there's a better way to handle all of this.

First, an essentially untyped interface with a void * argument is
bad.  Second, we can do all this with invalidate_inode_pages2_range()
and invalidate_mapping_pages() without introducing a new function.

Here's the proposal:

void super_drop_pagecache(struct super_block *sb,
		int (*invalidate)(struct address_space *, pgoff_t start, pgoff_t end))

In fs/drop-caches.c:

static void drop_pagecache_sb(struct super_block *sb, void *unused)
{
	super_drop_pagecache(sb, invalidate_mapping_pages);
}

In XFS:

		super_drop_pagecache(mp->m_super,
				invalidate_inode_pages2_range);

Much smaller change ...