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mm/rmap: introduce and use hugetlb_try_share_anon_rmap()

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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.

Add sanity checks that we end up with the right folios in the right
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.

Link: https://lkml.kernel.org/r/20231220224504.646757-6-david@redhat.com
Signed-off-by: David Hildenbrand <david@redhat.com>
Reviewed-by: Yin Fengwei <fengwei.yin@intel.com>
Reviewed-by: Ryan Roberts <ryan.roberts@arm.com>
Cc: Hugh Dickins <hughd@google.com>
Cc: Matthew Wilcox (Oracle) <willy@infradead.org>
Cc: Muchun Song <muchun.song@linux.dev>
Cc: Muchun Song <songmuchun@bytedance.com>
Cc: Peter Xu <peterx@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
This commit is contained in:
David Hildenbrand 2023-12-20 23:44:29 +01:00 committed by Andrew Morton
parent ebe2e35ec0
commit 0c2ec32bf0
2 changed files with 35 additions and 5 deletions
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25
include/linux/rmap.h
View File

@ -227,6 +227,30 @@ 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_hugetlb(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_hugetlb(folio), folio);
@ -331,6 +355,7 @@ dup:
*/
static inline int page_try_share_anon_rmap(struct page *page)
{
VM_WARN_ON(folio_test_hugetlb(page_folio(page)));
VM_BUG_ON_PAGE(!PageAnon(page) || !PageAnonExclusive(page), page);
/* device private pages cannot get pinned via GUP. */

11
mm/rmap.c
View File

@ -2149,12 +2149,17 @@ 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 (folio_test_hugetlb(folio)) {
if (anon_exclusive &&
page_try_share_anon_rmap(subpage)) {
if (folio_test_hugetlb(folio))
hugetlb_try_share_anon_rmap(folio)) {
set_huge_pte_at(mm, address, pvmw.pte,
pteval, hsz);
else
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);