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authorDavid Hildenbrand <david@redhat.com>2024-02-14 23:44:27 +0300
committerAndrew Morton <akpm@linux-foundation.org>2024-02-23 02:27:17 +0300
commit0cf18e839f64fff9a58569cc9a596bf97310e044 (patch)
tree1de1e7ebca6bc4f0a9a89fd1a97052b201b962c3 /mm/memory.c
parent789753e17c4d6593932f07e40b740373123296a6 (diff)
downloadlinux-0cf18e839f64fff9a58569cc9a596bf97310e044.tar.xz
mm/memory: handle !page case in zap_present_pte() separately
We don't need uptodate accessed/dirty bits, so in theory we could replace ptep_get_and_clear_full() by an optimized ptep_clear_full() function. Let's rely on the provided pte. Further, there is no scenario where we would have to insert uffd-wp markers when zapping something that is not a normal page (i.e., zeropage). Add a sanity check to make sure this remains true. should_zap_folio() no longer has to handle NULL pointers. This change replaces 2/3 "!page/!folio" checks by a single "!page" one. Note that arch_check_zapped_pte() on x86-64 checks the HW-dirty bit to detect shadow stack entries. But for shadow stack entries, the HW dirty bit (in combination with non-writable PTEs) is set by software. So for the arch_check_zapped_pte() check, we don't have to sync against HW setting the HW dirty bit concurrently, it is always set. Link: https://lkml.kernel.org/r/20240214204435.167852-3-david@redhat.com Signed-off-by: David Hildenbrand <david@redhat.com> Reviewed-by: Ryan Roberts <ryan.roberts@arm.com> Cc: Alexander Gordeev <agordeev@linux.ibm.com> Cc: Aneesh Kumar K.V <aneesh.kumar@linux.ibm.com> Cc: Arnd Bergmann <arnd@arndb.de> Cc: Catalin Marinas <catalin.marinas@arm.com> Cc: Christian Borntraeger <borntraeger@linux.ibm.com> Cc: Christophe Leroy <christophe.leroy@csgroup.eu> Cc: Heiko Carstens <hca@linux.ibm.com> Cc: Matthew Wilcox (Oracle) <willy@infradead.org> Cc: Michael Ellerman <mpe@ellerman.id.au> Cc: Michal Hocko <mhocko@suse.com> Cc: "Naveen N. Rao" <naveen.n.rao@linux.ibm.com> Cc: Nicholas Piggin <npiggin@gmail.com> Cc: Peter Zijlstra (Intel) <peterz@infradead.org> Cc: Sven Schnelle <svens@linux.ibm.com> Cc: Vasily Gorbik <gor@linux.ibm.com> Cc: Will Deacon <will@kernel.org> Cc: Yin Fengwei <fengwei.yin@intel.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Diffstat (limited to 'mm/memory.c')
-rw-r--r--mm/memory.c22
1 files changed, 11 insertions, 11 deletions
diff --git a/mm/memory.c b/mm/memory.c
index 6712453888fa..2b1e9abbe1e0 100644
--- a/mm/memory.c
+++ b/mm/memory.c
@@ -1499,10 +1499,6 @@ static inline bool should_zap_folio(struct zap_details *details,
if (should_zap_cows(details))
return true;
- /* E.g. the caller passes NULL for the case of a zero folio */
- if (!folio)
- return true;
-
/* Otherwise we should only zap non-anon folios */
return !folio_test_anon(folio);
}
@@ -1540,24 +1536,28 @@ static inline void zap_present_pte(struct mmu_gather *tlb,
int *rss, bool *force_flush, bool *force_break)
{
struct mm_struct *mm = tlb->mm;
- struct folio *folio = NULL;
bool delay_rmap = false;
+ struct folio *folio;
struct page *page;
page = vm_normal_page(vma, addr, ptent);
- if (page)
- folio = page_folio(page);
+ if (!page) {
+ /* We don't need up-to-date accessed/dirty bits. */
+ ptep_get_and_clear_full(mm, addr, pte, tlb->fullmm);
+ arch_check_zapped_pte(vma, ptent);
+ tlb_remove_tlb_entry(tlb, pte, addr);
+ VM_WARN_ON_ONCE(userfaultfd_wp(vma));
+ ksm_might_unmap_zero_page(mm, ptent);
+ return;
+ }
+ folio = page_folio(page);
if (unlikely(!should_zap_folio(details, folio)))
return;
ptent = ptep_get_and_clear_full(mm, addr, pte, tlb->fullmm);
arch_check_zapped_pte(vma, ptent);
tlb_remove_tlb_entry(tlb, pte, addr);
zap_install_uffd_wp_if_needed(vma, addr, pte, details, ptent);
- if (unlikely(!page)) {
- ksm_might_unmap_zero_page(mm, ptent);
- return;
- }
if (!folio_test_anon(folio)) {
if (pte_dirty(ptent)) {