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Subject[PATCH v4 7/6] iommu/iova: Make cached_node always valid
Date
With the anchor node at the top of the rbtree, there is always a valid
node for rb_next() to return, such that cached_node is only ever NULL
until the first allocation. Initialising it to point at the anchor node
gets rid of that window and makes the NULL checking entirely redundant.

Signed-off-by: Robin Murphy <robin.murphy@arm.com>
---

Oops, spotted this one slightly too late. This could be squashed into
patch #5 (which I'll do myself if I there's any cause to resend the
whole series again).

Robin.

drivers/iommu/iova.c | 12 +++---------
1 file changed, 3 insertions(+), 9 deletions(-)

diff --git a/drivers/iommu/iova.c b/drivers/iommu/iova.c
index a7af8273fa98..ec443c0a8319 100644
--- a/drivers/iommu/iova.c
+++ b/drivers/iommu/iova.c
@@ -51,7 +51,7 @@ init_iova_domain(struct iova_domain *iovad, unsigned long granule,

spin_lock_init(&iovad->iova_rbtree_lock);
iovad->rbroot = RB_ROOT;
- iovad->cached_node = NULL;
+ iovad->cached_node = &iovad->anchor.node;
iovad->cached32_node = NULL;
iovad->granule = granule;
iovad->start_pfn = start_pfn;
@@ -120,10 +120,7 @@ __get_cached_rbnode(struct iova_domain *iovad, unsigned long limit_pfn)
if (limit_pfn <= iovad->dma_32bit_pfn && iovad->cached32_node)
return iovad->cached32_node;

- if (iovad->cached_node)
- return iovad->cached_node;
-
- return &iovad->anchor.node;
+ return iovad->cached_node;
}

static void
@@ -141,14 +138,11 @@ __cached_rbnode_delete_update(struct iova_domain *iovad, struct iova *free)
struct iova *cached_iova;
struct rb_node **curr;

- if (free->pfn_hi < iovad->dma_32bit_pfn)
+ if (free->pfn_hi < iovad->dma_32bit_pfn && iovad->cached32_node)
curr = &iovad->cached32_node;
else
curr = &iovad->cached_node;

- if (!*curr)
- return;
-
cached_iova = rb_entry(*curr, struct iova, node);
if (free->pfn_lo >= cached_iova->pfn_lo)
*curr = rb_next(&free->node);
--
2.13.4.dirty
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