diff options
| author | David Hildenbrand <david@redhat.com> | 2023-04-11 16:25:12 +0200 |
|---|---|---|
| committer | Andrew Morton <akpm@linux-foundation.org> | 2023-04-18 16:30:01 -0700 |
| commit | 1462c52e9f2b99e72022ed8979bfc969894bb3da (patch) | |
| tree | c1164f150dcf0fb1d8e3ba158b4e67d6a45080c5 /mm/huge_memory.c | |
| parent | 5436d6556937de6236ffa1829550d13702569dab (diff) | |
| download | linux-1462c52e9f2b99e72022ed8979bfc969894bb3da.tar.gz | |
mm/huge_memory: conditionally call maybe_mkwrite() and drop pte_wrprotect() in __split_huge_pmd_locked()
No need to call maybe_mkwrite() to then wrprotect if the source PMD was not
writable.
It's worth nothing that this now allows for PTEs to be writable even if
the source PMD was not writable: if vma->vm_page_prot includes write
permissions.
As documented in commit 931298e103c2 ("mm/userfaultfd: rely on
vma->vm_page_prot in uffd_wp_range()"), any mechanism that intends to
have pages wrprotected (COW, writenotify, mprotect, uffd-wp, softdirty,
...) has to properly adjust vma->vm_page_prot upfront, to not include
write permissions. If vma->vm_page_prot includes write permissions, the
PTE/PMD can be writable as default.
This now mimics the handling in mm/migrate.c:remove_migration_pte() and in
mm/huge_memory.c:remove_migration_pmd(), which has been in place for a
long time (except that 96a9c287e25d ("mm/migrate: fix wrongly apply write
bit after mkdirty on sparc64") temporarily changed it).
Link: https://lkml.kernel.org/r/20230411142512.438404-7-david@redhat.com
Signed-off-by: David Hildenbrand <david@redhat.com>
Cc: Anshuman Khandual <anshuman.khandual@arm.com>
Cc: David S. Miller <davem@davemloft.net>
Cc: Hugh Dickins <hughd@google.com>
Cc: Peter Xu <peterx@redhat.com>
Cc: Sam Ravnborg <sam@ravnborg.org>
Cc: Shuah Khan <shuah@kernel.org>
Cc: Yu Zhao <yuzhao@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Diffstat (limited to 'mm/huge_memory.c')
| -rw-r--r-- | mm/huge_memory.c | 5 |
1 files changed, 2 insertions, 3 deletions
diff --git a/mm/huge_memory.c b/mm/huge_memory.c index 5700b1c727b69..c23fa39dec928 100644 --- a/mm/huge_memory.c +++ b/mm/huge_memory.c @@ -2233,11 +2233,10 @@ static void __split_huge_pmd_locked(struct vm_area_struct *vma, pmd_t *pmd, entry = pte_swp_mkuffd_wp(entry); } else { entry = mk_pte(page + i, READ_ONCE(vma->vm_page_prot)); - entry = maybe_mkwrite(entry, vma); + if (write) + entry = maybe_mkwrite(entry, vma); if (anon_exclusive) SetPageAnonExclusive(page + i); - if (!write) - entry = pte_wrprotect(entry); if (!young) entry = pte_mkold(entry); /* NOTE: this may set soft-dirty too on some archs */ |