Messages in this thread Patch in this message | | | Date | Mon, 3 Aug 2009 13:22:53 +0100 (BST) | From | Hugh Dickins <> | Subject | [PATCH 12/12] ksm: remove VM_MERGEABLE_FLAGS |
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KSM originally stood for Kernel Shared Memory: but the kernel has long supported shared memory, and VM_SHARED and VM_MAYSHARE vmas, and KSM is something else. So we switched to saying "merge" instead of "share".
But Chris Wright points out that this is confusing where mmap.c merges adjacent vmas: most especially in the name VM_MERGEABLE_FLAGS, used by is_mergeable_vma() to let vmas be merged despite flags being different.
Call it VMA_MERGE_DESPITE_FLAGS? Perhaps, but at present it consists only of VM_CAN_NONLINEAR: so for now it's clearer on all sides to use that directly, with a comment on it in is_mergeable_vma().
Signed-off-by: Hugh Dickins <hugh.dickins@tiscali.co.uk> --- This patch got lost along the way last time: no big deal but try again.
mm/mmap.c | 6 ++---- 1 file changed, 2 insertions(+), 4 deletions(-)
--- ksm11/mm/mmap.c 2009-08-02 13:50:41.000000000 +0100 +++ ksm12/mm/mmap.c 2009-08-02 13:51:04.000000000 +0100 @@ -660,9 +660,6 @@ again: remove_next = 1 + (end > next-> validate_mm(mm); } -/* Flags that can be inherited from an existing mapping when merging */ -#define VM_MERGEABLE_FLAGS (VM_CAN_NONLINEAR) - /* * If the vma has a ->close operation then the driver probably needs to release * per-vma resources, so we don't attempt to merge those. @@ -670,7 +667,8 @@ again: remove_next = 1 + (end > next-> static inline int is_mergeable_vma(struct vm_area_struct *vma, struct file *file, unsigned long vm_flags) { - if ((vma->vm_flags ^ vm_flags) & ~VM_MERGEABLE_FLAGS) + /* VM_CAN_NONLINEAR may get set later by f_op->mmap() */ + if ((vma->vm_flags ^ vm_flags) & ~VM_CAN_NONLINEAR) return 0; if (vma->vm_file != file) return 0;
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