Re: [PATCH v9 3/3] mm, pmem, xfs: Introduce MF_MEM_REMOVE for unbind

From: Matthew Wilcox <willy@infradead.org>
To: Shiyang Ruan <ruansy.fnst@fujitsu.com>
Cc: linux-kernel@vger.kernel.org, linux-xfs@vger.kernel.org,
	nvdimm@lists.linux.dev, linux-mm@kvack.org,
	linux-fsdevel@vger.kernel.org, djwong@kernel.org,
	dan.j.williams@intel.com, david@fromorbit.com, hch@infradead.org,
	jane.chu@oracle.com
Subject: Re: [PATCH v9 3/3] mm, pmem, xfs: Introduce MF_MEM_REMOVE for unbind
Date: Sun, 5 Feb 2023 21:10:41 +0000	[thread overview]
Message-ID: <Y+AbUZoj7hLobLXK@casper.infradead.org> (raw)
In-Reply-To: <1675522718-88-4-git-send-email-ruansy.fnst@fujitsu.com>

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 ...