diff options
Diffstat (limited to 'include/linux')
| -rw-r--r-- | include/linux/mm.h | 28 |
1 files changed, 28 insertions, 0 deletions
diff --git a/include/linux/mm.h b/include/linux/mm.h index 03776aab3837..fea113d1d723 100644 --- a/include/linux/mm.h +++ b/include/linux/mm.h @@ -528,6 +528,34 @@ extern unsigned int kobjsize(const void *objp); #define VM_FLAGS_CLEAR (ARCH_VM_PKEY_FLAGS | VM_ARCH_CLEAR) /* + * Flags which should be 'sticky' on merge - that is, flags which, when one VMA + * possesses it but the other does not, the merged VMA should nonetheless have + * applied to it: + * + * VM_MAYBE_GUARD - If a VMA may have guard regions in place it implies that + * mapped page tables may contain metadata not described by the + * VMA and thus any merged VMA may also contain this metadata, + * and thus we must make this flag sticky. + */ +#define VM_STICKY VM_MAYBE_GUARD + +/* + * VMA flags we ignore for the purposes of merge, i.e. one VMA possessing one + * of these flags and the other not does not preclude a merge. + * + * VM_SOFTDIRTY - Should not prevent from VMA merging, if we match the flags but + * dirty bit -- the caller should mark merged VMA as dirty. If + * dirty bit won't be excluded from comparison, we increase + * pressure on the memory system forcing the kernel to generate + * new VMAs when old one could be extended instead. + * + * VM_STICKY - When merging VMAs, VMA flags must match, unless they are + * 'sticky'. If any sticky flags exist in either VMA, we simply + * set all of them on the merged VMA. + */ +#define VM_IGNORE_MERGE (VM_SOFTDIRTY | VM_STICKY) + +/* * mapping from the currently active vm_flags protection bits (the * low four bits) to a page protection mask.. */ |