[PATCH 1/1] Revert "iommu/iova: Retry from last rb tree node if iova search fails"

[Zhen Lei <thunder.leizhen@huawei.com>]

This reverts commit 4e89dce725213d3d0b0475211b500eda4ef4bf2f.

We find that this patch has a great impact on performance. According to
our test: the iops decreases from 1655.6K to 893.5K, about half.

Hardware: 1 SAS expander with 12 SAS SSD
Command:  Only the main parameters are listed.
          fio bs=4k rw=read iodepth=128 cpus_allowed=0-127

Fixes: 4e89dce72521 ("iommu/iova: Retry from last rb tree node if iova search fails")
Tested-by: Xiang Chen <chenxiang66@hisilicon.com>
Signed-off-by: Zhen Lei <thunder.leizhen@huawei.com>
---
 drivers/iommu/iova.c | 23 ++++++-----------------
 1 file changed, 6 insertions(+), 17 deletions(-)

diff --git a/drivers/iommu/iova.c b/drivers/iommu/iova.c
index d20b8b333d30d17..f840c7207efbced 100644
--- a/drivers/iommu/iova.c
+++ b/drivers/iommu/iova.c
@@ -185,9 +185,8 @@ static int __alloc_and_insert_iova_range(struct iova_domain *iovad,
 	struct rb_node *curr, *prev;
 	struct iova *curr_iova;
 	unsigned long flags;
-	unsigned long new_pfn, retry_pfn;
+	unsigned long new_pfn;
 	unsigned long align_mask = ~0UL;
-	unsigned long high_pfn = limit_pfn, low_pfn = iovad->start_pfn;
 
 	if (size_aligned)
 		align_mask <<= fls_long(size - 1);
@@ -200,25 +199,15 @@ static int __alloc_and_insert_iova_range(struct iova_domain *iovad,
 
 	curr = __get_cached_rbnode(iovad, limit_pfn);
 	curr_iova = rb_entry(curr, struct iova, node);
-	retry_pfn = curr_iova->pfn_hi + 1;
-
-retry:
 	do {
-		high_pfn = min(high_pfn, curr_iova->pfn_lo);
-		new_pfn = (high_pfn - size) & align_mask;
+		limit_pfn = min(limit_pfn, curr_iova->pfn_lo);
+		new_pfn = (limit_pfn - size) & align_mask;
 		prev = curr;
 		curr = rb_prev(curr);
 		curr_iova = rb_entry(curr, struct iova, node);
-	} while (curr && new_pfn <= curr_iova->pfn_hi && new_pfn >= low_pfn);
-
-	if (high_pfn < size || new_pfn < low_pfn) {
-		if (low_pfn == iovad->start_pfn && retry_pfn < limit_pfn) {
-			high_pfn = limit_pfn;
-			low_pfn = retry_pfn;
-			curr = &iovad->anchor.node;
-			curr_iova = rb_entry(curr, struct iova, node);
-			goto retry;
-		}
+	} while (curr && new_pfn <= curr_iova->pfn_hi);
+
+	if (limit_pfn < size || new_pfn < iovad->start_pfn) {
 		iovad->max32_alloc_size = size;
 		goto iova32_full;
 	}
-- 
1.8.3


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