Commit 8314c4f2 authored Sep 21, 2009 by Hugh Dickins Committed by Linus Torvalds Sep 22, 2009

ksm: remove VM_MERGEABLE_FLAGS

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>

parent 7701c9c0

mm/mmap.c

+2 −4

Original line number	Diff line number	Diff line
		@@ -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;

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