# \[PATCH 03/15\] bvec: add a bvec\_kmap\_local helper

- From: Christoph Hellwig \<hch@lst.de\>
- Date: 2021-07-27 06:04:38 
- List: linuxppc-dev
- Page: https://ratatoskr.run/linuxppc-dev/2021/07/1459079
- Thread: https://ratatoskr.run/linux-mips/2021/07/1459073/t.md

```text
Add a helper to call kmap_local_page on a bvec.  There is no need for
an unmap helper given that kunmap_local accept any address in the mapped
page.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Chaitanya Kulkarni <redacted>
Reviewed-by: Martin K. Petersen <redacted>
Reviewed-by: Ira Weiny <redacted>
---
 include/linux/bvec.h | 13 +++++++++++++
 1 file changed, 13 insertions(+)

diff --git a/include/linux/bvec.h b/include/linux/bvec.h
index 883faf5f1523..f8710af18eef 100644
--- a/include/linux/bvec.h
+++ b/include/linux/bvec.h
@@ -7,6 +7,7 @@
 #ifndef __LINUX_BVEC_H
 #define __LINUX_BVEC_H
 
+#include <linux/highmem.h>
 #include <linux/bug.h>
 #include <linux/errno.h>
 #include <linux/limits.h>
@@ -183,4 +184,16 @@ static inline void bvec_advance(const struct bio_vec *bvec,
 	}
 }
 
+/**
+ * bvec_kmap_local - map a bvec into the kernel virtual address space
+ * @bvec: bvec to map
+ *
+ * Must be called on single-page bvecs only.  Call kunmap_local on the returned
+ * address to unmap.
+ */
+static inline void *bvec_kmap_local(struct bio_vec *bvec)
+{
+	return kmap_local_page(bvec->bv_page) + bvec->bv_offset;
+}
+
 #endif /* __LINUX_BVEC_H */
-- 
2.30.2

```