[PATCH] fixup! mm/hugetlb: Make walk_hugetlb_range() safe to pmd unshare
From: Peter Xu
Date: Tue Dec 06 2022 - 11:38:47 EST
Signed-off-by: Peter Xu <peterx@xxxxxxxxxx>
---
arch/s390/mm/gmap.c | 2 ++
fs/proc/task_mmu.c | 2 ++
include/linux/pagewalk.h | 8 +++++++-
mm/hmm.c | 8 +++++++-
4 files changed, 18 insertions(+), 2 deletions(-)
diff --git a/arch/s390/mm/gmap.c b/arch/s390/mm/gmap.c
index 8947451ae021..292a54c490d4 100644
--- a/arch/s390/mm/gmap.c
+++ b/arch/s390/mm/gmap.c
@@ -2643,7 +2643,9 @@ static int __s390_enable_skey_hugetlb(pte_t *pte, unsigned long addr,
end = start + HPAGE_SIZE - 1;
__storage_key_init_range(start, end);
set_bit(PG_arch_1, &page->flags);
+ hugetlb_vma_unlock_read(walk->vma);
cond_resched();
+ hugetlb_vma_lock_read(walk->vma);
return 0;
}
diff --git a/fs/proc/task_mmu.c b/fs/proc/task_mmu.c
index 89338950afd3..d7155f3bb678 100644
--- a/fs/proc/task_mmu.c
+++ b/fs/proc/task_mmu.c
@@ -1612,7 +1612,9 @@ static int pagemap_hugetlb_range(pte_t *ptep, unsigned long hmask,
frame++;
}
+ hugetlb_vma_unlock_read(walk->vma);
cond_resched();
+ hugetlb_vma_lock_read(walk->vma);
return err;
}
diff --git a/include/linux/pagewalk.h b/include/linux/pagewalk.h
index 959f52e5867d..1f7c2011f6cb 100644
--- a/include/linux/pagewalk.h
+++ b/include/linux/pagewalk.h
@@ -21,7 +21,13 @@ struct mm_walk;
* depth is -1 if not known, 0:PGD, 1:P4D, 2:PUD, 3:PMD.
* Any folded depths (where PTRS_PER_P?D is equal to 1)
* are skipped.
- * @hugetlb_entry: if set, called for each hugetlb entry
+ * @hugetlb_entry: if set, called for each hugetlb entry. Note that
+ * currently the hook function is protected by hugetlb
+ * vma lock to make sure pte_t* and the spinlock is valid
+ * to access. If the hook function needs to yield the
+ * thread or retake the vma lock for some reason, it
+ * needs to properly release the vma lock manually,
+ * and retake it before the function returns.
* @test_walk: caller specific callback function to determine whether
* we walk over the current vma or not. Returning 0 means
* "do page table walk over the current vma", returning
diff --git a/mm/hmm.c b/mm/hmm.c
index 3850fb625dda..dcd624f28bcf 100644
--- a/mm/hmm.c
+++ b/mm/hmm.c
@@ -493,8 +493,14 @@ static int hmm_vma_walk_hugetlb_entry(pte_t *pte, unsigned long hmask,
required_fault =
hmm_pte_need_fault(hmm_vma_walk, pfn_req_flags, cpu_flags);
if (required_fault) {
+ int ret;
+
spin_unlock(ptl);
- return hmm_vma_fault(addr, end, required_fault, walk);
+ hugetlb_vma_unlock_read(vma);
+ /* hmm_vma_fault() can retake the vma lock */
+ ret = hmm_vma_fault(addr, end, required_fault, walk);
+ hugetlb_vma_lock_read(vma);
+ return ret;
}
pfn = pte_pfn(entry) + ((start & ~hmask) >> PAGE_SHIFT);
--
2.37.3
--cAL/YfRa6VIe+3z7--