[bug report] mm: allow compound zone device pages

[Dan Carpenter <dan.carpenter@xxxxxxxxxx>]

Hello Alistair Popple,

This is a semi-automatic email about new static checker warnings.

Commit 04cabee2d411 ("mm: allow compound zone device pages") from Jan
7, 2025, leads to the following Smatch complaint:

    mm/migrate_device.c:157 migrate_vma_collect_pmd()
    warn: variable dereferenced before check 'page' (see line 156)

mm/migrate_device.c
   155				page = vm_normal_page(migrate->vma, addr, pte);
   156				pgmap = page_pgmap(page);
                                                   ^^^^
Unchecked dereference

   157				if (page && !is_zone_device_page(page) &&
                                    ^^^^
Too late

   158				    !(migrate->flags & MIGRATE_VMA_SELECT_SYSTEM))
   159					goto next;

regards,
dan carpenter