diff options
| author |   Peter Xu <peterx@redhat.com> | 2022-05-12 20:22:53 -0700 |
|---|---|---|
| committer |   Andrew Morton <akpm@linux-foundation.org> | 2022-05-13 07:20:10 -0700 |
| commit | 999dad824c39ed14dee7c4412aae531ba9e74a90 (patch) | |
| tree | 902b71da56121147d613e6ba249157ca5563e143 /include/linux/mm.h | |
| parent | mm/shmem: handle uffd-wp special pte in page fault handler (diff) | |
| download | wireguard-linux-999dad824c39ed14dee7c4412aae531ba9e74a90.tar.xz wireguard-linux-999dad824c39ed14dee7c4412aae531ba9e74a90.zip | |
mm/shmem: persist uffd-wp bit across zapping for file-backed
File-backed memory is prone to being unmapped at any time. It means all
information in the pte will be dropped, including the uffd-wp flag.
To persist the uffd-wp flag, we'll use the pte markers. This patch
teaches the zap code to understand uffd-wp and know when to keep or drop
the uffd-wp bit.
Add a new flag ZAP_FLAG_DROP_MARKER and set it in zap_details when we
don't want to persist such an information, for example, when destroying
the whole vma, or punching a hole in a shmem file. For the rest cases we
should never drop the uffd-wp bit, or the wr-protect information will get
lost.
The new ZAP_FLAG_DROP_MARKER needs to be put into mm.h rather than
memory.c because it'll be further referenced in hugetlb files later.
Link: https://lkml.kernel.org/r/20220405014847.14295-1-peterx@redhat.com
Signed-off-by: Peter Xu <peterx@redhat.com>
Cc: Alistair Popple <apopple@nvidia.com>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: Axel Rasmussen <axelrasmussen@google.com>
Cc: David Hildenbrand <david@redhat.com>
Cc: Hugh Dickins <hughd@google.com>
Cc: Jerome Glisse <jglisse@redhat.com>
Cc: "Kirill A . Shutemov" <kirill@shutemov.name>
Cc: Matthew Wilcox <willy@infradead.org>
Cc: Mike Kravetz <mike.kravetz@oracle.com>
Cc: Mike Rapoport <rppt@linux.vnet.ibm.com>
Cc: Nadav Amit <nadav.amit@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Diffstat (limited to 'include/linux/mm.h')
| -rw-r--r-- | include/linux/mm.h | 10 |
1 files changed, 10 insertions, 0 deletions
diff --git a/include/linux/mm.h b/include/linux/mm.h index d63ba0e0e068..61786259e52a 100644 --- a/include/linux/mm.h +++ b/include/linux/mm.h @@ -3428,4 +3428,14 @@ madvise_set_anon_name(struct mm_struct *mm, unsigned long start, } #endif +typedef unsigned int __bitwise zap_flags_t; + +/* + * Whether to drop the pte markers, for example, the uffd-wp information for + * file-backed memory. This should only be specified when we will completely + * drop the page in the mm, either by truncation or unmapping of the vma. By + * default, the flag is not set. + */ +#define ZAP_FLAG_DROP_MARKER ((__force zap_flags_t) BIT(0)) + #endif /* _LINUX_MM_H */ |