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Commit ad939deb authored by Suren Baghdasaryan's avatar Suren Baghdasaryan Committed by Gerrit - the friendly Code Review server
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ANDROID: mm: remove sequence counting when mmap_lock is not exclusively owned 



In a number of cases vm_write_{begin|end} is called while mmap_lock is
not owned exclusively. This is unnecessary and can affect correctness of
the sequence counting protecting speculative page fault handlers. Remove
extra calls.

Bug: 257443051
Change-Id: I1278638a0794448e22fbdab5601212b3b2eaebdc
Signed-off-by: default avatarSuren Baghdasaryan <surenb@google.com>
Git-commit: bfdcf47ca34dc3b7b63ca16b0a1856e57c57ee47
Git-repo: https://android.googlesource.com/kernel/common/


[quic_c_spathi@quicinc.com: resolve trivial merge conflicts]
Signed-off-by: default avatarSrinivasarao Pathipati <quic_c_spathi@quicinc.com>
parent 365a5b7a

mm/madvise.c

+0 −6
Original line number Diff line number Diff line
@@ -500,11 +500,9 @@ static void madvise_cold_page_range(struct mmu_gather *tlb, 
		.target_task = task,

	};



	vm_write_begin(vma);

	tlb_start_vma(tlb, vma);

	walk_page_range(vma->vm_mm, addr, end, &cold_walk_ops, &walk_private);

	tlb_end_vma(tlb, vma);

	vm_write_end(vma);

}



static long madvise_cold(struct task_struct *task,
@@ -538,11 +536,9 @@ static void madvise_pageout_page_range(struct mmu_gather *tlb, 
		.target_task = task,

	};



	vm_write_begin(vma);

	tlb_start_vma(tlb, vma);

	walk_page_range(vma->vm_mm, addr, end, &cold_walk_ops, &walk_private);

	tlb_end_vma(tlb, vma);

	vm_write_end(vma);

}



static inline bool can_do_pageout(struct vm_area_struct *vma)
@@ -745,12 +741,10 @@ static int madvise_free_single_vma(struct vm_area_struct *vma, 
	update_hiwater_rss(mm);



	mmu_notifier_invalidate_range_start(&range);

	vm_write_begin(vma);

	tlb_start_vma(&tlb, vma);

	walk_page_range(vma->vm_mm, range.start, range.end,

			&madvise_free_walk_ops, &tlb);

	tlb_end_vma(&tlb, vma);

	vm_write_end(vma);

	mmu_notifier_invalidate_range_end(&range);

	tlb_finish_mmu(&tlb, range.start, range.end);

mm/memory.c

+0 −2
Original line number Diff line number Diff line
@@ -1292,7 +1292,6 @@ void unmap_page_range(struct mmu_gather *tlb, 
	unsigned long next;



	BUG_ON(addr >= end);

	vm_write_begin(vma);

	tlb_start_vma(tlb, vma);

	pgd = pgd_offset(vma->vm_mm, addr);

	do {
@@ -1302,7 +1301,6 @@ void unmap_page_range(struct mmu_gather *tlb, 
		next = zap_p4d_range(tlb, vma, pgd, addr, next, details);

	} while (pgd++, addr = next, addr != end);

	tlb_end_vma(tlb, vma);

	vm_write_end(vma);

}

mm/mempolicy.c

+0 −2
Original line number Diff line number Diff line
@@ -599,11 +599,9 @@ unsigned long change_prot_numa(struct vm_area_struct *vma, 
{

	int nr_updated;



	vm_write_begin(vma);

	nr_updated = change_protection(vma, addr, end, PAGE_NONE, 0, 1);

	if (nr_updated)

		count_vm_numa_events(NUMA_PTE_UPDATES, nr_updated);

	vm_write_end(vma);



	return nr_updated;

}