@@ -13,7 +13,8 @@ static inline bool not_found(struct page_vma_mapped_walk *pvmw)
return false;
}
-static bool map_pte(struct page_vma_mapped_walk *pvmw, spinlock_t **ptlp)
+static bool map_pte(struct page_vma_mapped_walk *pvmw, pmd_t *pmdvalp,
+ spinlock_t **ptlp)
{
pte_t ptent;
@@ -25,6 +26,7 @@ static bool map_pte(struct page_vma_mapped_walk *pvmw, spinlock_t **ptlp)
return !!pvmw->pte;
}
+again:
/*
* It is important to return the ptl corresponding to pte,
* in case *pvmw->pmd changes underneath us; so we need to
@@ -32,8 +34,8 @@ static bool map_pte(struct page_vma_mapped_walk *pvmw, spinlock_t **ptlp)
* proceeds to loop over next ptes, and finds a match later.
* Though, in most cases, page lock already protects this.
*/
- pvmw->pte = pte_offset_map_nolock(pvmw->vma->vm_mm, pvmw->pmd,
- pvmw->address, ptlp);
+ pvmw->pte = pte_offset_map_rw_nolock(pvmw->vma->vm_mm, pvmw->pmd,
+ pvmw->address, pmdvalp, ptlp);
if (!pvmw->pte)
return false;
@@ -67,8 +69,13 @@ static bool map_pte(struct page_vma_mapped_walk *pvmw, spinlock_t **ptlp)
} else if (!pte_present(ptent)) {
return false;
}
+ spin_lock(*ptlp);
+ if (unlikely(!pmd_same(*pmdvalp, pmdp_get_lockless(pvmw->pmd)))) {
+ pte_unmap_unlock(pvmw->pte, *ptlp);
+ goto again;
+ }
pvmw->ptl = *ptlp;
- spin_lock(pvmw->ptl);
+
return true;
}
@@ -278,7 +285,7 @@ bool page_vma_mapped_walk(struct page_vma_mapped_walk *pvmw)
step_forward(pvmw, PMD_SIZE);
continue;
}
- if (!map_pte(pvmw, &ptl)) {
+ if (!map_pte(pvmw, &pmde, &ptl)) {
if (!pvmw->pte)
goto restart;
goto next_pte;
@@ -305,8 +312,13 @@ bool page_vma_mapped_walk(struct page_vma_mapped_walk *pvmw)
} while (pte_none(ptep_get(pvmw->pte)));
if (!pvmw->ptl) {
+ spin_lock(ptl);
+ if (unlikely(!pmd_same(pmde, pmdp_get_lockless(pvmw->pmd)))) {
+ pte_unmap_unlock(pvmw->pte, ptl);
+ pvmw->pte = NULL;
+ goto restart;
+ }
pvmw->ptl = ptl;
- spin_lock(pvmw->ptl);
}
goto this_pte;
} while (pvmw->address < end);
In the caller of map_pte(), we may modify the pvmw->pte after acquiring the pvmw->ptl, so convert it to using pte_offset_map_rw_nolock(). At this time, the pte_same() check is not performed after the pvmw->ptl held, so we should get pmdval and do pmd_same() check to ensure the stability of pvmw->pmd. Signed-off-by: Qi Zheng <zhengqi.arch@bytedance.com> --- mm/page_vma_mapped.c | 24 ++++++++++++++++++------ 1 file changed, 18 insertions(+), 6 deletions(-)