diff options
author | Peter Xu | 2022-05-12 20:22:52 -0700 |
---|---|---|
committer | Andrew Morton | 2022-05-13 07:20:09 -0700 |
commit | f46f2adecdcc1ba0799383e67fe98f65f41fea5c (patch) | |
tree | 094d394291c6a27df284d3ea46bda996b23344aa /include | |
parent | 5c041f5d1f23d3a172dd0db3215634c484b4acd6 (diff) |
mm: check against orig_pte for finish_fault()
This patch allows do_fault() to trigger on !pte_none() cases too. This
prepares for the pte markers to be handled by do_fault() just like none
pte.
To achieve this, instead of unconditionally check against pte_none() in
finish_fault(), we may hit the case that the orig_pte was some pte marker
so what we want to do is to replace the pte marker with some valid pte
entry. Then if orig_pte was set we'd want to check the current *pte
(under pgtable lock) against orig_pte rather than none pte.
Right now there's no solid way to safely reference orig_pte because when
pmd is not allocated handle_pte_fault() will not initialize orig_pte, so
it's not safe to reference it.
There's another solution proposed before this patch to do pte_clear() for
vmf->orig_pte for pmd==NULL case, however it turns out it'll break arm32
because arm32 could have assumption that pte_t* pointer will always reside
on a real ram32 pgtable, not any kernel stack variable.
To solve this, we add a new flag FAULT_FLAG_ORIG_PTE_VALID, and it'll be
set along with orig_pte when there is valid orig_pte, or it'll be cleared
when orig_pte was not initialized.
It'll be updated every time we call handle_pte_fault(), so e.g. if a page
fault retry happened it'll be properly updated along with orig_pte.
[1] https://lore.kernel.org/lkml/710c48c9-406d-e4c5-a394-10501b951316@samsung.com/
[akpm@linux-foundation.org: coding-style cleanups]
[peterx@redhat.com: fix crash reported by Marek]
Link: https://lkml.kernel.org/r/Ylb9rXJyPm8/ao8f@xz-m1.local
Link: https://lkml.kernel.org/r/20220405014836.14077-1-peterx@redhat.com
Signed-off-by: Peter Xu <peterx@redhat.com>
Reviewed-by: Alistair Popple <apopple@nvidia.com>
Tested-by: Marek Szyprowski <m.szyprowski@samsung.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')
-rw-r--r-- | include/linux/mm_types.h | 3 |
1 files changed, 3 insertions, 0 deletions
diff --git a/include/linux/mm_types.h b/include/linux/mm_types.h index 7216d77a5884..dd382270ae40 100644 --- a/include/linux/mm_types.h +++ b/include/linux/mm_types.h @@ -822,6 +822,8 @@ typedef struct { * @FAULT_FLAG_UNSHARE: The fault is an unsharing request to unshare (and mark * exclusive) a possibly shared anonymous page that is * mapped R/O. + * @FAULT_FLAG_ORIG_PTE_VALID: whether the fault has vmf->orig_pte cached. + * We should only access orig_pte if this flag set. * * About @FAULT_FLAG_ALLOW_RETRY and @FAULT_FLAG_TRIED: we can specify * whether we would allow page faults to retry by specifying these two @@ -858,6 +860,7 @@ enum fault_flag { FAULT_FLAG_INSTRUCTION = 1 << 8, FAULT_FLAG_INTERRUPTIBLE = 1 << 9, FAULT_FLAG_UNSHARE = 1 << 10, + FAULT_FLAG_ORIG_PTE_VALID = 1 << 11, }; #endif /* _LINUX_MM_TYPES_H */ |