[SCSI] block: add sg buffer copy helper functions
This patch adds new three helper functions to copy data between an SG
list and a linear buffer.
- sg_copy_from_buffer copies data from linear buffer to an SG list
- sg_copy_to_buffer copies data from an SG list to a linear buffer
When the APIs copy data from a linear buffer to an SG list,
flush_kernel_dcache_page is called. It's not necessary for everyone
but it's a no-op on most architectures and in general the API is not
used in performance critical path.
Signed-off-by: FUJITA Tomonori <fujita.tomonori@lab.ntt.co.jp>
Acked-by: Jens Axboe <jens.axboe@oracle.com>
Signed-off-by: James Bottomley <James.Bottomley@HansenPartnership.com>
diff --git a/include/linux/scatterlist.h b/include/linux/scatterlist.h
index a3d567a..71fc813 100644
--- a/include/linux/scatterlist.h
+++ b/include/linux/scatterlist.h
@@ -213,6 +213,11 @@
sg_alloc_fn *);
int sg_alloc_table(struct sg_table *, unsigned int, gfp_t);
+size_t sg_copy_from_buffer(struct scatterlist *sgl, unsigned int nents,
+ void *buf, size_t buflen);
+size_t sg_copy_to_buffer(struct scatterlist *sgl, unsigned int nents,
+ void *buf, size_t buflen);
+
/*
* Maximum number of entries that will be allocated in one piece, if
* a list larger than this is required then chaining will be utilized.