scatterlist: introduce sg_unmark_end

This is useful in places that recycle the same scatterlist multiple
times, and do not want to incur the cost of sg_init_table every
time in hot paths.

Acked-by: Jens Axboe <axboe@kernel.dk>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>

diff --git a/block/blk-integrity.c b/block/blk-integrity.c
index dabd221..03cf717 100644 (file)
--- a/block/blk-integrity.c
+++ b/block/blk-integrity.c
@@ -110,7 +110,7 @@ new_segment:
                        if (!sg)
                                sg = sglist;
                        else {
-                               sg->page_link &= ~0x02;
+                               sg_unmark_end(sg);
                                sg = sg_next(sg);
                        }
 

diff --git a/block/blk-merge.c b/block/blk-merge.c
index 936a110..5f24482 100644 (file)
--- a/block/blk-merge.c
+++ b/block/blk-merge.c
@@ -143,7 +143,7 @@ new_segment:
                         * termination bit to avoid doing a full
                         * sg_init_table() in drivers for each command.
                         */
-                       (*sg)->page_link &= ~0x02;
+                       sg_unmark_end(*sg);
                        *sg = sg_next(*sg);
                }
 

diff --git a/include/linux/scatterlist.h b/include/linux/scatterlist.h
index 2d8bdae..bfc47e0 100644 (file)
--- a/include/linux/scatterlist.h
+++ b/include/linux/scatterlist.h
@@ -172,6 +172,22 @@ static inline void sg_mark_end(struct scatterlist *sg)
 }
 
 /**
+ * sg_unmark_end - Undo setting the end of the scatterlist
+ * @sg:                 SG entryScatterlist
+ *
+ * Description:
+ *   Removes the termination marker from the given entry of the scatterlist.
+ *
+ **/
+static inline void sg_unmark_end(struct scatterlist *sg)
+{
+#ifdef CONFIG_DEBUG_SG
+       BUG_ON(sg->sg_magic != SG_MAGIC);
+#endif
+       sg->page_link &= ~0x02;
+}
+
+/**
  * sg_phys - Return physical address of an sg entry
  * @sg:             SG entry
  *