On 2024/8/21 17:17, LEROY Christophe wrote:
Le 21/08/2024 à 10:18, Qi Zheng a écrit :
In handle_pte_fault(), we may modify the vmf->pte after acquiring the
vmf->ptl, so convert it to using pte_offset_map_maywrite_nolock(). But
since we already do the pte_same() check, so there is no need to get
pmdval to do pmd_same() check, just pass NULL to pmdvalp parameter.
Signed-off-by: Qi Zheng <zhengqi.arch@xxxxxxxxxxxxx>
---
mm/memory.c | 9 +++++++--
1 file changed, 7 insertions(+), 2 deletions(-)
diff --git a/mm/memory.c b/mm/memory.c
index 93c0c25433d02..d3378e98faf13 100644
--- a/mm/memory.c
+++ b/mm/memory.c
@@ -5504,9 +5504,14 @@ static vm_fault_t handle_pte_fault(struct vm_fault *vmf)
* pmd by anon khugepaged, since that takes mmap_lock in write
* mode; but shmem or file collapse to THP could still morph
* it into a huge pmd: just retry later if so.
+ *
+ * Use the maywrite version to indicate that vmf->pte will be
+ * modified, but since we will use pte_same() to detect the
+ * change of the pte entry, there is no need to get pmdval.
*/
- vmf->pte = pte_offset_map_nolock(vmf->vma->vm_mm, vmf->pmd,
- vmf->address, &vmf->ptl);
+ vmf->pte = pte_offset_map_maywrite_nolock(vmf->vma->vm_mm,
+ vmf->pmd, vmf->address,
+ NULL, &vmf->ptl);
This might be the demonstration that the function name is becoming too long.
Can you find shorter names ?
Maybe use abbreviations?
pte_offset_map_ro_nolock()
pte_offset_map_rw_nolock()
if (unlikely(!vmf->pte))
return 0;
vmf->orig_pte = ptep_get_lockless(vmf->pte);
