path: root/kernel/fork.c
diff options
authorEric B Munson <>2015-11-05 18:51:36 -0800
committerLinus Torvalds <>2015-11-05 19:34:48 -0800
commitde60f5f10c58d4f34b68622442c0e04180367f3f (patch)
treebe0a15ded3c2177e26e69c316bf730d393e6357a /kernel/fork.c
parenta8ca5d0ecbdde5cc3d7accacbd69968b0c98764e (diff)
mm: introduce VM_LOCKONFAULT
The cost of faulting in all memory to be locked can be very high when working with large mappings. If only portions of the mapping will be used this can incur a high penalty for locking. For the example of a large file, this is the usage pattern for a large statical language model (probably applies to other statical or graphical models as well). For the security example, any application transacting in data that cannot be swapped out (credit card data, medical records, etc). This patch introduces the ability to request that pages are not pre-faulted, but are placed on the unevictable LRU when they are finally faulted in. The VM_LOCKONFAULT flag will be used together with VM_LOCKED and has no effect when set without VM_LOCKED. Setting the VM_LOCKONFAULT flag for a VMA will cause pages faulted into that VMA to be added to the unevictable LRU when they are faulted or if they are already present, but will not cause any missing pages to be faulted in. Exposing this new lock state means that we cannot overload the meaning of the FOLL_POPULATE flag any longer. Prior to this patch it was used to mean that the VMA for a fault was locked. This means we need the new FOLL_MLOCK flag to communicate the locked state of a VMA. FOLL_POPULATE will now only control if the VMA should be populated and in the case of VM_LOCKONFAULT, it will not be set. Signed-off-by: Eric B Munson <> Acked-by: Kirill A. Shutemov <> Acked-by: Vlastimil Babka <> Cc: Michal Hocko <> Cc: Jonathan Corbet <> Cc: Catalin Marinas <> Cc: Geert Uytterhoeven <> Cc: Guenter Roeck <> Cc: Heiko Carstens <> Cc: Michael Kerrisk <> Cc: Ralf Baechle <> Cc: Shuah Khan <> Cc: Stephen Rothwell <> Signed-off-by: Andrew Morton <> Signed-off-by: Linus Torvalds <>
Diffstat (limited to 'kernel/fork.c')
1 files changed, 2 insertions, 1 deletions
diff --git a/kernel/fork.c b/kernel/fork.c
index 6ac894244d39..a30fae45b486 100644
--- a/kernel/fork.c
+++ b/kernel/fork.c
@@ -454,7 +454,8 @@ static int dup_mmap(struct mm_struct *mm, struct mm_struct *oldmm)
tmp->vm_mm = mm;
if (anon_vma_fork(tmp, mpnt))
goto fail_nomem_anon_vma_fork;
- tmp->vm_flags &= ~(VM_LOCKED|VM_UFFD_MISSING|VM_UFFD_WP);
+ tmp->vm_flags &=
tmp->vm_next = tmp->vm_prev = NULL;
tmp->vm_userfaultfd_ctx = NULL_VM_UFFD_CTX;
file = tmp->vm_file;