[PATCH 2/3] swiotlb: consolidate rounding up default_nslabs

From: Chao Gao
Date: Fri Jul 15 2022 - 06:45:57 EST


default_nslabs are rounded up in two cases with exactly same comments.
Add a simple wrapper to reduce duplicate code/comments. It is preparatory
to adding more logics into the round-up.

No functional change intended.

Signed-off-by: Chao Gao <chao.gao@xxxxxxxxx>
---
kernel/dma/swiotlb.c | 34 ++++++++++++++++++----------------
1 file changed, 18 insertions(+), 16 deletions(-)

diff --git a/kernel/dma/swiotlb.c b/kernel/dma/swiotlb.c
index 0d0f99146360..9ab87d6d47bc 100644
--- a/kernel/dma/swiotlb.c
+++ b/kernel/dma/swiotlb.c
@@ -88,6 +88,22 @@ struct io_tlb_area {
spinlock_t lock;
};

+/*
+ * Round up number of slabs to the next power of 2. The last area is going
+ * be smaller than the rest if default_nslabs is not power of two.
+ *
+ * Return true if default_nslabs is rounded up.
+ */
+static bool round_up_default_nslabs(void)
+{
+ if (!default_nareas || is_power_of_2(default_nslabs))
+ return false;
+
+ default_nslabs = roundup_pow_of_two(default_nslabs);
+
+ return true;
+}
+
static void swiotlb_adjust_nareas(unsigned int nareas)
{
if (!is_power_of_2(nareas))
@@ -96,16 +112,9 @@ static void swiotlb_adjust_nareas(unsigned int nareas)
default_nareas = nareas;

pr_info("area num %d.\n", nareas);
- /*
- * Round up number of slabs to the next power of 2.
- * The last area is going be smaller than the rest if
- * default_nslabs is not power of two.
- */
- if (nareas && !is_power_of_2(default_nslabs)) {
- default_nslabs = roundup_pow_of_two(default_nslabs);
+ if (round_up_default_nslabs())
pr_info("SWIOTLB bounce buffer size roundup to %luMB",
(default_nslabs << IO_TLB_SHIFT) >> 20);
- }
}

static int __init
@@ -154,17 +163,10 @@ void __init swiotlb_adjust_size(unsigned long size)
if (default_nslabs != IO_TLB_DEFAULT_SIZE >> IO_TLB_SHIFT)
return;

- /*
- * Round up number of slabs to the next power of 2.
- * The last area is going be smaller than the rest if
- * default_nslabs is not power of two.
- */
size = ALIGN(size, IO_TLB_SIZE);
default_nslabs = ALIGN(size >> IO_TLB_SHIFT, IO_TLB_SEGSIZE);
- if (default_nareas) {
- default_nslabs = roundup_pow_of_two(default_nslabs);
+ if (round_up_default_nslabs())
size = default_nslabs << IO_TLB_SHIFT;
- }

pr_info("SWIOTLB bounce buffer size adjusted to %luMB", size >> 20);
}
--
2.25.1