[PATCH 1/2] mm,swap: extract swap single page readahead into its own function

[Rik van Riel]

Split swap single page readahead into its own function, to make
the next patch easier to read. No functional changes.

Signed-off-by: Rik van Riel <r...@surriel.com>
---
 mm/swap_state.c | 40 +++++++++++++++++++++++++---------------
 1 file changed, 25 insertions(+), 15 deletions(-)

diff --git a/mm/swap_state.c b/mm/swap_state.c
index c16eebb81d8b..aacb9ba53f63 100644
--- a/mm/swap_state.c
+++ b/mm/swap_state.c
@@ -594,6 +594,28 @@ static unsigned long swapin_nr_pages(unsigned long offset)
        return pages;
 }
 
+static struct page *swap_cluster_read_one(swp_entry_t entry,
+               unsigned long offset, gfp_t gfp_mask,
+               struct vm_area_struct *vma, unsigned long addr, bool readahead)
+{
+       bool page_allocated;
+       struct page *page;
+
+       page =__read_swap_cache_async(swp_entry(swp_type(entry), offset),
+                                     gfp_mask, vma, addr, &page_allocated);
+       if (!page)
+               return NULL;
+       if (page_allocated) {
+               swap_readpage(page, false);
+               if (readahead) {
+                       SetPageReadahead(page);
+                       count_vm_event(SWAP_RA);
+               }
+       }
+       put_page(page);
+       return page;
+}
+
 /**
  * swap_cluster_readahead - swap in pages in hope we need them soon
  * @entry: swap entry of this memory
@@ -615,14 +637,13 @@ static unsigned long swapin_nr_pages(unsigned long offset)
 struct page *swap_cluster_readahead(swp_entry_t entry, gfp_t gfp_mask,
                                struct vm_fault *vmf)
 {
-       struct page *page;
        unsigned long entry_offset = swp_offset(entry);
        unsigned long offset = entry_offset;
        unsigned long start_offset, end_offset;
        unsigned long mask;
        struct swap_info_struct *si = swp_swap_info(entry);
        struct blk_plug plug;
-       bool do_poll = true, page_allocated;
+       bool do_poll = true;
        struct vm_area_struct *vma = vmf->vma;
        unsigned long addr = vmf->address;
 
@@ -649,19 +670,8 @@ struct page *swap_cluster_readahead(swp_entry_t entry, 
gfp_t gfp_mask,
        blk_start_plug(&plug);
        for (offset = start_offset; offset <= end_offset ; offset++) {
                /* Ok, do the async read-ahead now */
-               page = __read_swap_cache_async(
-                       swp_entry(swp_type(entry), offset),
-                       gfp_mask, vma, addr, &page_allocated);
-               if (!page)
-                       continue;
-               if (page_allocated) {
-                       swap_readpage(page, false);
-                       if (offset != entry_offset) {
-                               SetPageReadahead(page);
-                               count_vm_event(SWAP_RA);
-                       }
-               }
-               put_page(page);
+               swap_cluster_read_one(entry, offset, gfp_mask, vma, addr,
+                                     offset != entry_offset);
        }
        blk_finish_plug(&plug);
 
-- 
2.25.4