[PATCH v4 09/13] mm: mremap: move_ptes() use pte_offset_map_rw_nolock()

[Muchun Song]

> On Sep 24, 2024, at 14:10, Qi Zheng <zhengqi.arch at bytedance.com> wrote:
> 
> In move_ptes(), we may modify the new_pte after acquiring the new_ptl, so
> convert it to using pte_offset_map_rw_nolock(). Now new_pte is none, so
> hpage_collapse_scan_file() path can not find this by traversing
> file->f_mapping, so there is no concurrency with retract_page_tables(). In
> addition, we already hold the exclusive mmap_lock, so this new_pte page is
> stable, so there is no need to get pmdval and do pmd_same() check.
> 
> Signed-off-by: Qi Zheng <zhengqi.arch at bytedance.com>

Reviewed-by: Muchun Song <muchun.song at linux.dev>