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.a...@bytedance.com> --- 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);
