| Message ID | 20231211155652.131054-6-david@redhat.com (mailing list archive) |
|---|---|
| State | New |
| Headers | show |
| Series | mm/rmap: interface overhaul | expand |
On 11/12/2023 15:56, David Hildenbrand wrote: > hugetlb rmap handling differs quite a lot from "ordinary" rmap code. > For example, hugetlb currently only supports entire mappings, and treats > any mapping as mapped using a single "logical PTE". Let's move it out > of the way so we can overhaul our "ordinary" rmap. > implementation/interface. > > So let's introduce and use hugetlb_try_dup_anon_rmap() to make all > hugetlb handling use dedicated hugetlb_* rmap functions. > > Note that try_to_unmap_one() does not need care. Easy to spot because > among all that nasty hugetlb special-casing in that function, we're not > using set_huge_pte_at() on the anon path -- well, and that code assumes > that we would want to swapout. > > Reviewed-by: Yin Fengwei <fengwei.yin@intel.com> > Signed-off-by: David Hildenbrand <david@redhat.com> Reviewed-by: Ryan Roberts <ryan.roberts@arm.com> > --- > include/linux/rmap.h | 23 +++++++++++++++++++++++ > mm/rmap.c | 15 ++++++++++----- > 2 files changed, 33 insertions(+), 5 deletions(-) > > diff --git a/include/linux/rmap.h b/include/linux/rmap.h > index ca42b3db5688..4c0650e9f6db 100644 > --- a/include/linux/rmap.h > +++ b/include/linux/rmap.h > @@ -228,6 +228,29 @@ static inline int hugetlb_try_dup_anon_rmap(struct folio *folio, > return 0; > } > > +/* See page_try_share_anon_rmap() */ > +static inline int hugetlb_try_share_anon_rmap(struct folio *folio) > +{ > + VM_WARN_ON_FOLIO(!folio_test_anon(folio), folio); > + VM_WARN_ON_FOLIO(!PageAnonExclusive(&folio->page), folio); > + > + /* Paired with the memory barrier in try_grab_folio(). */ > + if (IS_ENABLED(CONFIG_HAVE_FAST_GUP)) > + smp_mb(); > + > + if (unlikely(folio_maybe_dma_pinned(folio))) > + return -EBUSY; > + ClearPageAnonExclusive(&folio->page); > + > + /* > + * This is conceptually a smp_wmb() paired with the smp_rmb() in > + * gup_must_unshare(). > + */ > + if (IS_ENABLED(CONFIG_HAVE_FAST_GUP)) > + smp_mb__after_atomic(); > + return 0; > +} > + > static inline void hugetlb_add_file_rmap(struct folio *folio) > { > VM_WARN_ON_FOLIO(folio_test_anon(folio), folio); > diff --git a/mm/rmap.c b/mm/rmap.c > index 4e60c1f38eaa..e210ac1b73de 100644 > --- a/mm/rmap.c > +++ b/mm/rmap.c > @@ -2147,13 +2147,18 @@ static bool try_to_migrate_one(struct folio *folio, struct vm_area_struct *vma, > !anon_exclusive, subpage); > > /* See page_try_share_anon_rmap(): clear PTE first. */ > - if (anon_exclusive && > - page_try_share_anon_rmap(subpage)) { > - if (folio_test_hugetlb(folio)) > + if (folio_test_hugetlb(folio)) { > + if (anon_exclusive && > + hugetlb_try_share_anon_rmap(folio)) { > set_huge_pte_at(mm, address, pvmw.pte, > pteval, hsz); > - else > - set_pte_at(mm, address, pvmw.pte, pteval); > + ret = false; > + page_vma_mapped_walk_done(&pvmw); > + break; > + } > + } else if (anon_exclusive && > + page_try_share_anon_rmap(subpage)) { > + set_pte_at(mm, address, pvmw.pte, pteval); > ret = false; > page_vma_mapped_walk_done(&pvmw); > break;
diff --git a/include/linux/rmap.h b/include/linux/rmap.h index ca42b3db5688..4c0650e9f6db 100644 --- a/include/linux/rmap.h +++ b/include/linux/rmap.h @@ -228,6 +228,29 @@ static inline int hugetlb_try_dup_anon_rmap(struct folio *folio, return 0; } +/* See page_try_share_anon_rmap() */ +static inline int hugetlb_try_share_anon_rmap(struct folio *folio) +{ + VM_WARN_ON_FOLIO(!folio_test_anon(folio), folio); + VM_WARN_ON_FOLIO(!PageAnonExclusive(&folio->page), folio); + + /* Paired with the memory barrier in try_grab_folio(). */ + if (IS_ENABLED(CONFIG_HAVE_FAST_GUP)) + smp_mb(); + + if (unlikely(folio_maybe_dma_pinned(folio))) + return -EBUSY; + ClearPageAnonExclusive(&folio->page); + + /* + * This is conceptually a smp_wmb() paired with the smp_rmb() in + * gup_must_unshare(). + */ + if (IS_ENABLED(CONFIG_HAVE_FAST_GUP)) + smp_mb__after_atomic(); + return 0; +} + static inline void hugetlb_add_file_rmap(struct folio *folio) { VM_WARN_ON_FOLIO(folio_test_anon(folio), folio); diff --git a/mm/rmap.c b/mm/rmap.c index 4e60c1f38eaa..e210ac1b73de 100644 --- a/mm/rmap.c +++ b/mm/rmap.c @@ -2147,13 +2147,18 @@ static bool try_to_migrate_one(struct folio *folio, struct vm_area_struct *vma, !anon_exclusive, subpage); /* See page_try_share_anon_rmap(): clear PTE first. */ - if (anon_exclusive && - page_try_share_anon_rmap(subpage)) { - if (folio_test_hugetlb(folio)) + if (folio_test_hugetlb(folio)) { + if (anon_exclusive && + hugetlb_try_share_anon_rmap(folio)) { set_huge_pte_at(mm, address, pvmw.pte, pteval, hsz); - else - set_pte_at(mm, address, pvmw.pte, pteval); + ret = false; + page_vma_mapped_walk_done(&pvmw); + break; + } + } else if (anon_exclusive && + page_try_share_anon_rmap(subpage)) { + set_pte_at(mm, address, pvmw.pte, pteval); ret = false; page_vma_mapped_walk_done(&pvmw); break;