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

[Matthew Wilcox]

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 ...