Commit 0af50bea authored Nov 21, 2022 by Suren Baghdasaryan Committed by Srinivasarao Pathipati Mar 14, 2023

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: Suren Baghdasaryan <surenb@google.com>
Git-commit: 5ed391bd8ad8481d82c1bbb05a35f5538966dce9
Git-repo: https://android.googlesource.com/kernel/common/


[quic_c_spathi@quicinc.com: resolve trivial merge conflicts]
Signed-off-by: Srinivasarao Pathipati <quic_c_spathi@quicinc.com>

parent 53d30c2a

mm/khugepaged.c

+2 −0

Original line number	Diff line number	Diff line
		@@ -1294,10 +1294,12 @@ 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));
		}