On 2024/8/21 17:17, LEROY Christophe wrote:

Le 21/08/2024 à 10:18, Qi Zheng a écrit :

quoted

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 <redacted>
---
   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()

quoted

   		if (unlikely(!vmf->pte))
   			return 0;
   		vmf->orig_pte = ptep_get_lockless(vmf->pte);