Commit 2441774f authored by Qi Zheng's avatar Qi Zheng Committed by Andrew Morton
Browse files

mm: multi-gen LRU: walk_pte_range() use pte_offset_map_rw_nolock() 

In walk_pte_range(), we may modify the pte entry after holding the ptl, so
convert it to using pte_offset_map_rw_nolock().  At this time, the
pte_same() check is not performed after the ptl held, so we should get
pmdval and do pmd_same() check to ensure the stability of pmd entry.

Link: https://lkml.kernel.org/r/7e9c194a5efacc9609cfd31abb9c7df88b53b530.1727332572.git.zhengqi.arch@bytedance.com


Signed-off-by: default avatarQi Zheng <zhengqi.arch@bytedance.com>
Reviewed-by: default avatarMuchun Song <muchun.song@linux.dev>
Acked-by: default avatarDavid Hildenbrand <david@redhat.com>
Cc: Hugh Dickins <hughd@google.com>
Cc: Matthew Wilcox <willy@infradead.org>
Cc: Mike Rapoport (Microsoft) <rppt@kernel.org>
Cc: Peter Xu <peterx@redhat.com>
Cc: Ryan Roberts <ryan.roberts@arm.com>
Cc: Vishal Moola (Oracle) <vishal.moola@gmail.com>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
parent e9c74b54

mm/vmscan.c

+8 −1
Original line number Diff line number Diff line
@@ -3386,8 +3386,10 @@ static bool walk_pte_range(pmd_t *pmd, unsigned long start, unsigned long end, 
	struct pglist_data *pgdat = lruvec_pgdat(walk->lruvec);

	DEFINE_MAX_SEQ(walk->lruvec);

	int old_gen, new_gen = lru_gen_from_seq(max_seq);

	pmd_t pmdval;



	pte = pte_offset_map_nolock(args->mm, pmd, start & PMD_MASK, &ptl);

	pte = pte_offset_map_rw_nolock(args->mm, pmd, start & PMD_MASK, &pmdval,

				       &ptl);

	if (!pte)

		return false;

	if (!spin_trylock(ptl)) {
@@ -3395,6 +3397,11 @@ static bool walk_pte_range(pmd_t *pmd, unsigned long start, unsigned long end, 
		return false;

	}



	if (unlikely(!pmd_same(pmdval, pmdp_get_lockless(pmd)))) {

		pte_unmap_unlock(pte, ptl);

		return false;

	}



	arch_enter_lazy_mmu_mode();

restart:

	for (i = pte_index(start), addr = start; addr != end; i++, addr += PAGE_SIZE) {