[PATCH v2 1/9] 9p: Add a migrate_folio method

[David Howells]

Matthew Wilcox (Oracle) <willy at infradead.org> wrote:

> The migration code used to be able to migrate dirty 9p folios by writing
> them back using writepage.  When the writepage method was removed,
> we neglected to add a migrate_folio method, which means that dirty 9p
> folios have been unmovable ever since.  This reduced our success at
> defragmenting memory on machines which use 9p heavily.
> 
> Fixes: 80105ed2fd27 (9p: Use netfslib read/write_iter)
> Cc: stable at vger.kernel.org
> Cc: David Howells <dhowells at redhat.com>
> Cc: v9fs at lists.linux.dev
> Signed-off-by: Matthew Wilcox (Oracle) <willy at infradead.org>

Reviewed-by: David Howells <dhowells at redhat.com>