Commit de560423 authored by Nick Piggin's avatar Nick Piggin Committed by Linus Torvalds
Browse files

mm: percpu-vmap fix RCU list walking 



RCU list walking of the per-cpu vmap cache was broken.  It did not use
RCU primitives, and also the union of free_list and rcu_head is
obviously wrong (because free_list is indeed the list we are RCU
walking).

While we are there, remove a couple of unused fields from an earlier
iteration.

These APIs aren't actually used anywhere, because of problems with the
XFS conversion.  Christoph has now verified that the problems are solved
with these patches.  Also it is an exported interface, so I think it
will be good to be merged now (and Christoph wants to get the XFS
changes into their local tree).

Cc: stable@kernel.org
Cc: linux-mm@kvack.org
Tested-by: default avatarChristoph Hellwig <hch@infradead.org>
Signed-off-by: default avatarNick Piggin <npiggin@suse.de>
--
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent 489b24f2

mm/vmalloc.c

+6 −14
Original line number Diff line number Diff line
@@ -667,8 +667,6 @@ static bool vmap_initialized __read_mostly = false; 
struct vmap_block_queue {

	spinlock_t lock;

	struct list_head free;

	struct list_head dirty;

	unsigned int nr_dirty;

};



struct vmap_block {
@@ -678,11 +676,9 @@ struct vmap_block { 
	unsigned long free, dirty;

	DECLARE_BITMAP(alloc_map, VMAP_BBMAP_BITS);

	DECLARE_BITMAP(dirty_map, VMAP_BBMAP_BITS);

	union {

	struct list_head free_list;

	struct rcu_head rcu_head;

};

};



/* Queue of free and dirty vmap blocks, for allocation and flushing purposes */

static DEFINE_PER_CPU(struct vmap_block_queue, vmap_block_queue);
@@ -757,7 +753,7 @@ static struct vmap_block *new_vmap_block(gfp_t gfp_mask) 
	vbq = &get_cpu_var(vmap_block_queue);

	vb->vbq = vbq;

	spin_lock(&vbq->lock);

	list_add(&vb->free_list, &vbq->free);

	list_add_rcu(&vb->free_list, &vbq->free);

	spin_unlock(&vbq->lock);

	put_cpu_var(vmap_block_queue);
@@ -776,8 +772,6 @@ static void free_vmap_block(struct vmap_block *vb) 
	struct vmap_block *tmp;

	unsigned long vb_idx;



	BUG_ON(!list_empty(&vb->free_list));



	vb_idx = addr_to_vb_idx(vb->va->va_start);

	spin_lock(&vmap_block_tree_lock);

	tmp = radix_tree_delete(&vmap_block_tree, vb_idx);
@@ -816,7 +810,7 @@ again: 
			vb->free -= 1UL << order;

			if (vb->free == 0) {

				spin_lock(&vbq->lock);

				list_del_init(&vb->free_list);

				list_del_rcu(&vb->free_list);

				spin_unlock(&vbq->lock);

			}

			spin_unlock(&vb->lock);
@@ -860,11 +854,11 @@ static void vb_free(const void *addr, unsigned long size) 
	BUG_ON(!vb);



	spin_lock(&vb->lock);

	bitmap_allocate_region(vb->dirty_map, offset >> PAGE_SHIFT, order);

	BUG_ON(bitmap_allocate_region(vb->dirty_map, offset >> PAGE_SHIFT, order));



	vb->dirty += 1UL << order;

	if (vb->dirty == VMAP_BBMAP_BITS) {

		BUG_ON(vb->free || !list_empty(&vb->free_list));

		BUG_ON(vb->free);

		spin_unlock(&vb->lock);

		free_vmap_block(vb);

	} else
@@ -1033,8 +1027,6 @@ void __init vmalloc_init(void) 
		vbq = &per_cpu(vmap_block_queue, i);

		spin_lock_init(&vbq->lock);

		INIT_LIST_HEAD(&vbq->free);

		INIT_LIST_HEAD(&vbq->dirty);

		vbq->nr_dirty = 0;

	}



	/* Import existing vmlist entries. */

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