On Wed, 20 Sep 2023 15:32:42 -0700 Yang Shi <yang@xxxxxxxxxxxxxxxxxxxxxx> wrote:
> When calling mbind() with MPOL_MF_{MOVE|MOVEALL} | MPOL_MF_STRICT,
> kernel should attempt to migrate all existing pages, and return -EIO if
> there is misplaced or unmovable page. Then commit 6f4576e3687b
> ("mempolicy: apply page table walker on queue_pages_range()") messed up
> the return value and didn't break VMA scan early ianymore when MPOL_MF_STRICT
> alone. The return value problem was fixed by commit a7f40cfe3b7a
> ("mm: mempolicy: make mbind() return -EIO when MPOL_MF_STRICT is specified"),
> but it broke the VMA walk early if unmovable page is met, it may cause some
> pages are not migrated as expected.
So I'm thinking that a7f40cfe3b7a is the suitable Fixes: target?
> The code should conceptually do:
>
> if (MPOL_MF_MOVE|MOVEALL)
> scan all vmas
> try to migrate the existing pages
> return success
> else if (MPOL_MF_MOVE* | MPOL_MF_STRICT)
> scan all vmas
> try to migrate the existing pages
> return -EIO if unmovable or migration failed
> else /* MPOL_MF_STRICT alone */
> break early if meets unmovable and don't call mbind_range() at all
> else /* none of those flags */
> check the ranges in test_walk, EFAULT without mbind_range() if discontig.
>
> Fixed the behavior.
>
