Merge branch 'anonvma' (64a8920f) · Commits · 戴 / test

mm/mmap.c

+70 −40

Original line number	Diff line number	Diff line
		@@ -507,11 +507,12 @@ int vma_adjust(struct vm_area_struct *vma, unsigned long start,
		struct address_space *mapping = NULL;
		struct prio_tree_root *root = NULL;
		struct file *file = vma->vm_file;
		struct anon_vma *anon_vma = NULL;
		long adjust_next = 0;
		int remove_next = 0;

		if (next && !insert) {
		struct vm_area_struct *exporter = NULL;

		if (end >= next->vm_end) {
		/*
		* vma expands, overlapping all the next, and
		@@ -519,7 +520,7 @@ int vma_adjust(struct vm_area_struct *vma, unsigned long start,
		*/
		again: remove_next = 1 + (end > next->vm_end);
		end = next->vm_end;
		anon_vma = next->anon_vma;
		exporter = next;
		importer = vma;
		} else if (end > next->vm_start) {
		/*
		@@ -527,7 +528,7 @@ again: remove_next = 1 + (end > next->vm_end);
		* mprotect case 5 shifting the boundary up.
		*/
		adjust_next = (end - next->vm_start) >> PAGE_SHIFT;
		anon_vma = next->anon_vma;
		exporter = next;
		importer = vma;
		} else if (end < vma->vm_end) {
		/*
		@@ -536,28 +537,19 @@ again: remove_next = 1 + (end > next->vm_end);
		* mprotect case 4 shifting the boundary down.
		*/
		adjust_next = - ((vma->vm_end - end) >> PAGE_SHIFT);
		anon_vma = next->anon_vma;
		exporter = vma;
		importer = next;
		}
		}

		/*
		* When changing only vma->vm_end, we don't really need anon_vma lock.
		*/
		if (vma->anon_vma && (insert \|\| importer \|\| start != vma->vm_start))
		anon_vma = vma->anon_vma;
		if (anon_vma) {
		/*
		* Easily overlooked: when mprotect shifts the boundary,
		* make sure the expanding vma has anon_vma set if the
		* shrinking vma had, to cover any anon pages imported.
		*/
		if (importer && !importer->anon_vma) {
		/* Block reverse map lookups until things are set up. */
		if (anon_vma_clone(importer, vma)) {
		if (exporter && exporter->anon_vma && !importer->anon_vma) {
		if (anon_vma_clone(importer, exporter))
		return -ENOMEM;
		}
		importer->anon_vma = anon_vma;
		importer->anon_vma = exporter->anon_vma;
		}
		}

		@@ -824,6 +816,61 @@ struct vm_area_struct vma_merge(struct mm_struct mm,
		return NULL;
		}

		/*
		* Rough compatbility check to quickly see if it's even worth looking
		* at sharing an anon_vma.
		*
		* They need to have the same vm_file, and the flags can only differ
		* in things that mprotect may change.
		*
		* NOTE! The fact that we share an anon_vma doesn't _have_ to mean that
		* we can merge the two vma's. For example, we refuse to merge a vma if
		* there is a vm_ops->close() function, because that indicates that the
		* driver is doing some kind of reference counting. But that doesn't
		* really matter for the anon_vma sharing case.
		*/
		static int anon_vma_compatible(struct vm_area_struct a, struct vm_area_struct b)
		{
		return a->vm_end == b->vm_start &&
		mpol_equal(vma_policy(a), vma_policy(b)) &&
		a->vm_file == b->vm_file &&
		!((a->vm_flags ^ b->vm_flags) & ~(VM_READ\|VM_WRITE\|VM_EXEC)) &&
		b->vm_pgoff == a->vm_pgoff + ((b->vm_start - a->vm_start) >> PAGE_SHIFT);
		}

		/*
		* Do some basic sanity checking to see if we can re-use the anon_vma
		* from 'old'. The 'a'/'b' vma's are in VM order - one of them will be
		* the same as 'old', the other will be the new one that is trying
		* to share the anon_vma.
		*
		* NOTE! This runs with mm_sem held for reading, so it is possible that
		* the anon_vma of 'old' is concurrently in the process of being set up
		* by another page fault trying to merge _that_. But that's ok: if it
		* is being set up, that automatically means that it will be a singleton
		* acceptable for merging, so we can do all of this optimistically. But
		* we do that ACCESS_ONCE() to make sure that we never re-load the pointer.
		*
		* IOW: that the "list_is_singular()" test on the anon_vma_chain only
		* matters for the 'stable anon_vma' case (ie the thing we want to avoid
		* is to return an anon_vma that is "complex" due to having gone through
		* a fork).
		*
		* We also make sure that the two vma's are compatible (adjacent,
		* and with the same memory policies). That's all stable, even with just
		* a read lock on the mm_sem.
		*/
		static struct anon_vma reusable_anon_vma(struct vm_area_struct old, struct vm_area_struct a, struct vm_area_struct b)
		{
		if (anon_vma_compatible(a, b)) {
		struct anon_vma *anon_vma = ACCESS_ONCE(old->anon_vma);

		if (anon_vma && list_is_singular(&old->anon_vma_chain))
		return anon_vma;
		}
		return NULL;
		}

		/*
		* find_mergeable_anon_vma is used by anon_vma_prepare, to check
		* neighbouring vmas for a suitable anon_vma, before it goes off
		@@ -834,28 +881,16 @@ struct vm_area_struct vma_merge(struct mm_struct mm,
		*/
		struct anon_vma find_mergeable_anon_vma(struct vm_area_struct vma)
		{
		struct anon_vma *anon_vma;
		struct vm_area_struct *near;
		unsigned long vm_flags;

		near = vma->vm_next;
		if (!near)
		goto try_prev;

		/*
		* Since only mprotect tries to remerge vmas, match flags
		* which might be mprotected into each other later on.
		* Neither mlock nor madvise tries to remerge at present,
		* so leave their flags as obstructing a merge.
		*/
		vm_flags = vma->vm_flags & ~(VM_READ\|VM_WRITE\|VM_EXEC);
		vm_flags \|= near->vm_flags & (VM_READ\|VM_WRITE\|VM_EXEC);

		if (near->anon_vma && vma->vm_end == near->vm_start &&
		mpol_equal(vma_policy(vma), vma_policy(near)) &&
		can_vma_merge_before(near, vm_flags,
		NULL, vma->vm_file, vma->vm_pgoff +
		((vma->vm_end - vma->vm_start) >> PAGE_SHIFT)))
		return near->anon_vma;
		anon_vma = reusable_anon_vma(near, vma, near);
		if (anon_vma)
		return anon_vma;
		try_prev:
		/*
		* It is potentially slow to have to call find_vma_prev here.
		@@ -868,14 +903,9 @@ try_prev:
		if (!near)
		goto none;

		vm_flags = vma->vm_flags & ~(VM_READ\|VM_WRITE\|VM_EXEC);
		vm_flags \|= near->vm_flags & (VM_READ\|VM_WRITE\|VM_EXEC);

		if (near->anon_vma && near->vm_end == vma->vm_start &&
		mpol_equal(vma_policy(near), vma_policy(vma)) &&
		can_vma_merge_after(near, vm_flags,
		NULL, vma->vm_file, vma->vm_pgoff))
		return near->anon_vma;
		anon_vma = reusable_anon_vma(near, near, vma);
		if (anon_vma)
		return anon_vma;
		none:
		/*
		* There's no absolute need to look only at touching neighbours:

mm/rmap.c

+14 −3

Original line number	Diff line number	Diff line
		@@ -182,7 +182,7 @@ int anon_vma_clone(struct vm_area_struct dst, struct vm_area_struct src)
		{
		struct anon_vma_chain avc, pavc;

		list_for_each_entry(pavc, &src->anon_vma_chain, same_vma) {
		list_for_each_entry_reverse(pavc, &src->anon_vma_chain, same_vma) {
		avc = anon_vma_chain_alloc();
		if (!avc)
		goto enomem_failure;
		@@ -734,9 +734,20 @@ void page_move_anon_rmap(struct page *page,
		static void __page_set_anon_rmap(struct page *page,
		struct vm_area_struct *vma, unsigned long address)
		{
		struct anon_vma *anon_vma = vma->anon_vma;
		struct anon_vma_chain *avc;
		struct anon_vma *anon_vma;

		BUG_ON(!vma->anon_vma);

		/*
		* We must use the _oldest_ possible anon_vma for the page mapping!
		*
		* So take the last AVC chain entry in the vma, which is the deepest
		* ancestor, and use the anon_vma from that.
		*/
		avc = list_entry(vma->anon_vma_chain.prev, struct anon_vma_chain, same_vma);
		anon_vma = avc->anon_vma;

		BUG_ON(!anon_vma);
		anon_vma = (void *) anon_vma + PAGE_MAPPING_ANON;
		page->mapping = (struct address_space *) anon_vma;
		page->index = linear_page_index(vma, address);

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