mm: remove arch_flush_tlb_batched_pending() arch helper

Since commit 4b634918384c ("arm64/mm: Close theoretical race where stale
TLB entry remains valid"), all arches that use tlbbatch for reclaim
(arm64, riscv, x86) implement arch_flush_tlb_batched_pending() with a
flush_tlb_mm().

So let's simplify by removing the unnecessary abstraction and doing the
flush_tlb_mm() directly in flush_tlb_batched_pending(). This effectively
reverts commit db6c1f6f236d ("mm/tlbbatch: introduce
arch_flush_tlb_batched_pending()").

Link: https://lkml.kernel.org/r/[e-mail]
Signed-off-by: Ryan Roberts <[e-mail]>
Suggested-by: Will Deacon <[e-mail]>
Reviewed-by: Lorenzo Stoakes <[e-mail]>
Acked-by: David Hildenbrand <[e-mail]>
Reviewed-by: Anshuman Khandual <[e-mail]>
Acked-by: Will Deacon <[e-mail]>
Cc: Albert Ou <[e-mail]>
Cc: Alexandre Ghiti <[e-mail]>
Cc: Borislav Betkov <[e-mail]>
Cc: Catalin Marinas <[e-mail]>
Cc: "H. Peter Anvin" <[e-mail]>
Cc: Ingo Molnar <[e-mail]>
Cc: Liam Howlett <[e-mail]>
Cc: Lorenzo Stoakes <[e-mail]>
Cc: Palmer Dabbelt <[e-mail]>
Cc: Paul Walmsley <[e-mail]>
Cc: Rik van Riel <[e-mail]>
Cc: Ryan Roberts <[e-mail]>
Cc: Thomas Gleinxer <[e-mail]>
Cc: Vlastimil Babka <[e-mail]>
Signed-off-by: Andrew Morton <[e-mail]>

arch/arm64/include/asm/tlbflush.h

···
 }
 
 /*
- * If mprotect/munmap/etc occurs during TLB batched flushing, we need to ensure
- * all the previously issued TLBIs targeting mm have completed. But since we
- * can be executing on a remote CPU, a DSB cannot guarantee this like it can
- * for arch_tlbbatch_flush(). Our only option is to flush the entire mm.
- */
-static inline void arch_flush_tlb_batched_pending(struct mm_struct *mm)
-{
-	flush_tlb_mm(mm);
-}
-
-/*
  * To support TLB batched flush for multiple pages unmapping, we only send
  * the TLBI for each page in arch_tlbbatch_add_pending() and wait for the
  * completion at the end in arch_tlbbatch_flush(). Since we've already issued

arch/riscv/include/asm/tlbflush.h

···
 bool arch_tlbbatch_should_defer(struct mm_struct *mm);
 void arch_tlbbatch_add_pending(struct arch_tlbflush_unmap_batch *batch,
 		struct mm_struct *mm, unsigned long start, unsigned long end);
-void arch_flush_tlb_batched_pending(struct mm_struct *mm);
 void arch_tlbbatch_flush(struct arch_tlbflush_unmap_batch *batch);
 
 extern unsigned long tlb_flush_all_threshold;

arch/riscv/mm/tlbflush.c

···
 	mmu_notifier_arch_invalidate_secondary_tlbs(mm, start, end);
 }
 
-void arch_flush_tlb_batched_pending(struct mm_struct *mm)
-{
-	flush_tlb_mm(mm);
-}
-
 void arch_tlbbatch_flush(struct arch_tlbflush_unmap_batch *batch)
 {
 	__flush_tlb_range(NULL, &batch->cpumask,

arch/x86/include/asm/tlbflush.h

···
 	mmu_notifier_arch_invalidate_secondary_tlbs(mm, 0, -1UL);
 }
 
-static inline void arch_flush_tlb_batched_pending(struct mm_struct *mm)
-{
-	flush_tlb_mm(mm);
-}
-
 extern void arch_tlbbatch_flush(struct arch_tlbflush_unmap_batch *batch);
 
 static inline bool pte_flags_need_flush(unsigned long oldflags,

mm/rmap.c

···
 	int flushed = batch >> TLB_FLUSH_BATCH_FLUSHED_SHIFT;
 
 	if (pending != flushed) {
-		arch_flush_tlb_batched_pending(mm);
+		flush_tlb_mm(mm);
 		/*
 		 * If the new TLB flushing is pending during flushing, leave
 		 * mm->tlb_flush_batched as is, to avoid losing flushing.