minor improvement to abd_free_pages()

It doesn't need to have a loop to free page in a single scatterlist
entry because it should be single or compound page. The pages can be
freed in one invocation to __free_pages() for both cases.

Reviewed-by: Gvozden Neskovic <neskovic@gmail.com>
Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Reviewed-by: Richard Yao <ryao@gentoo.org>
Signed-off-by: Jinshan Xiong <jinshan.xiong@gmail.com>
Closes #6057

diff --git a/module/zfs/abd.c b/module/zfs/abd.c
index 6d0a3b5030808804d599ebdcbbeca9fecbe00b3c..765ac7fb72e6bea70a46050e2255e0feee9ca8fc 100644 (file)
--- a/module/zfs/abd.c
+++ b/module/zfs/abd.c
@@ -374,7 +374,7 @@ abd_free_pages(abd_t *abd)
        struct sg_table table;
        struct page *page;
        int nr_pages = ABD_SCATTER(abd).abd_nents;
-       int order, i, j;
+       int order, i;
 
        if (abd->abd_flags & ABD_FLAG_MULTI_ZONE)
                ABDSTAT_BUMPDOWN(abdstat_scatter_page_multi_zone);
@@ -383,13 +383,11 @@ abd_free_pages(abd_t *abd)
                ABDSTAT_BUMPDOWN(abdstat_scatter_page_multi_chunk);
 
        abd_for_each_sg(abd, sg, nr_pages, i) {
-               for (j = 0; j < sg->length; ) {
-                       page = nth_page(sg_page(sg), j >> PAGE_SHIFT);
-                       order = compound_order(page);
-                       __free_pages(page, order);
-                       j += (PAGESIZE << order);
-                       ABDSTAT_BUMPDOWN(abdstat_scatter_orders[order]);
-               }
+               page = sg_page(sg);
+               order = compound_order(page);
+               __free_pages(page, order);
+               ASSERT3U(sg->length, <=, PAGE_SIZE << order);
+               ABDSTAT_BUMPDOWN(abdstat_scatter_orders[order]);
        }
 
        table.sgl = ABD_SCATTER(abd).abd_sgl;