The quilt patch titled
Subject: mm: handle_pte_fault() use pte_offset_map_rw_nolock()
has been removed from the -mm tree. Its filename was
mm-handle_pte_fault-use-pte_offset_map_rw_nolock.patch
This patch was dropped because it was merged into the mm-stable branch
of git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm
------------------------------------------------------
From: Qi Zheng <zhengqi.arch@xxxxxxxxxxxxx>
Subject: mm: handle_pte_fault() use pte_offset_map_rw_nolock()
Date: Thu, 26 Sep 2024 14:46:19 +0800
In handle_pte_fault(), we may modify the vmf->pte after acquiring the
vmf->ptl, so convert it to using pte_offset_map_rw_nolock(). But since we
will do the pte_same() check, so there is no need to get pmdval to do
pmd_same() check, just pass a dummy variable to it.
Link: https://lkml.kernel.org/r/af8d694853b44c5a6018403ae435440e275854c7.1727332572.git.zhengqi.arch@xxxxxxxxxxxxx
Signed-off-by: Qi Zheng <zhengqi.arch@xxxxxxxxxxxxx>
Acked-by: David Hildenbrand <david@xxxxxxxxxx>
Reviewed-by: Muchun Song <muchun.song@xxxxxxxxx>
Cc: Hugh Dickins <hughd@xxxxxxxxxx>
Cc: Matthew Wilcox <willy@xxxxxxxxxxxxx>
Cc: Mike Rapoport (Microsoft) <rppt@xxxxxxxxxx>
Cc: Peter Xu <peterx@xxxxxxxxxx>
Cc: Ryan Roberts <ryan.roberts@xxxxxxx>
Cc: Vishal Moola (Oracle) <vishal.moola@xxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
mm/memory.c | 14 ++++++++++++--
1 file changed, 12 insertions(+), 2 deletions(-)
--- a/mm/memory.c~mm-handle_pte_fault-use-pte_offset_map_rw_nolock
+++ a/mm/memory.c
@@ -5742,14 +5742,24 @@ static vm_fault_t handle_pte_fault(struc
vmf->pte = NULL;
vmf->flags &= ~FAULT_FLAG_ORIG_PTE_VALID;
} else {
+ pmd_t dummy_pmdval;
+
/*
* A regular pmd is established and it can't morph into a huge
* 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 may be
+ * modified, but since we will use pte_same() to detect the
+ * change of the !pte_none() entry, there is no need to recheck
+ * the pmdval. Here we chooes to pass a dummy variable instead
+ * of NULL, which helps new user think about why this place is
+ * special.
*/
- vmf->pte = pte_offset_map_nolock(vmf->vma->vm_mm, vmf->pmd,
- vmf->address, &vmf->ptl);
+ vmf->pte = pte_offset_map_rw_nolock(vmf->vma->vm_mm, vmf->pmd,
+ vmf->address, &dummy_pmdval,
+ &vmf->ptl);
if (unlikely(!vmf->pte))
return 0;
vmf->orig_pte = ptep_get_lockless(vmf->pte);
_
Patches currently in -mm which might be from zhengqi.arch@xxxxxxxxxxxxx are
