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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>
Acked-by: Izik Eidus <ieidus@redhat.com>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Hugh Dickins 2009-09-21 17:02:25 -07:00 committed by Linus Torvalds
parent 7701c9c0f5
commit 8314c4f24a
1 changed files with 2 additions and 4 deletions
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6
mm/mmap.c
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@ -657,9 +657,6 @@ again: remove_next = 1 + (end > next->vm_end);
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.
@ -667,7 +664,8 @@ again: remove_next = 1 + (end > next->vm_end);
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;