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Commit 365a5b7a authored by Suren Baghdasaryan's avatar Suren Baghdasaryan Committed by Gerrit - the friendly Code Review server
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ANDROID: mm/khugepaged: add missing vm_write_{begin|end} 



Speculative page fault handler needs to detect concurrent pmd changes
and relies on vma seqcount for that. pmdp_collapse_flush(), set_huge_pmd() and collapse_and_free_pmd() can modify a pmd.
vm_write_{begin|end} are needed in the paths which can call these
functions for page fault handler to detect pmd changes.

Bug: 257443051
Change-Id: Ieb784b5f44901b66a594f61b9e7c91190ff97f80
Signed-off-by: default avatarSuren Baghdasaryan <surenb@google.com>
Git-commit: 5ed391bd8ad8481d82c1bbb05a35f5538966dce9
Git-repo: https://android.googlesource.com/kernel/common/


Signed-off-by: default avatarSrinivasarao Pathipati <quic_c_spathi@quicinc.com>
parent 5b5bd362

mm/khugepaged.c

+5 −0
Original line number Diff line number Diff line
@@ -1343,6 +1343,7 @@ void collapse_pte_mapped_thp(struct mm_struct *mm, unsigned long addr) 
	if (!pmd)

		goto drop_hpage;



	vm_write_begin(vma);

	start_pte = pte_offset_map_lock(mm, pmd, haddr, &ptl);



	/* step 1: check all mapped PTEs are to the right huge page */
@@ -1392,6 +1393,7 @@ void collapse_pte_mapped_thp(struct mm_struct *mm, unsigned long addr) 
	ptl = pmd_lock(vma->vm_mm, pmd);

	_pmd = pmdp_collapse_flush(vma, haddr, pmd);

	spin_unlock(ptl);

	vm_write_end(vma);

	mm_dec_nr_ptes(mm);

	pte_free(mm, pmd_pgtable(_pmd));
@@ -1402,6 +1404,7 @@ void collapse_pte_mapped_thp(struct mm_struct *mm, unsigned long addr) 


abort:

	pte_unmap_unlock(start_pte, ptl);

	vm_write_end(vma);

	goto drop_hpage;

}
@@ -1473,10 +1476,12 @@ static void retract_page_tables(struct address_space *mapping, pgoff_t pgoff) 
		 */

		if (down_write_trylock(&mm->mmap_sem)) {

			if (!khugepaged_test_exit(mm)) {

				vm_write_begin(vma);

				spinlock_t *ptl = pmd_lock(mm, pmd);

				/* assume page table is clear */

				_pmd = pmdp_collapse_flush(vma, addr, pmd);

				spin_unlock(ptl);

				vm_write_end(vma);

				mm_dec_nr_ptes(mm);

				pte_free(mm, pmd_pgtable(_pmd));

			}