mm-remove-compressed-copy-from-zram-in-memory-fix-2-fix

invert unlikely() test, augment comment, 80-col cleanup

Cc: Artem Savkov <artem.savkov@gmail.com>
Cc: Dan Magenheimer <dan.magenheimer@oracle.com>
Cc: Hugh Dickins <hughd@google.com>
Cc: Konrad Rzeszutek Wilk <konrad@darnok.org>
Cc: Minchan Kim <minchan@kernel.org>
Cc: Nitin Gupta <ngupta@vflare.org>
Cc: Seth Jennings <sjenning@linux.vnet.ibm.com>
Cc: Shaohua Li <shli@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

diff --git a/mm/page_io.c b/mm/page_io.c
index 2b76ac7422716d0a28d6ad619b85f3cca43ac44e..ba05b64e5d8ddfc19f31c046f7c0b735d099364b 100644 (file)
--- a/mm/page_io.c
+++ b/mm/page_io.c
@@ -81,51 +81,54 @@ void end_swap_bio_read(struct bio *bio, int err)
                                imajor(bio->bi_bdev->bd_inode),
                                iminor(bio->bi_bdev->bd_inode),
                                (unsigned long long)bio->bi_sector);
-       } else {
-               SetPageUptodate(page);
+               goto out;
+       }
 
-               /*
-                * There is no guarantee that the page is in swap cache, so
-                * we need to check PG_swapcache before proceeding with this
-                * optimization.
-                */
-               if (unlikely(PageSwapCache(page))) {
-                       struct swap_info_struct *sis;
-
-                       sis = page_swap_info(page);
-                       if (sis->flags & SWP_BLKDEV) {
-                               /*
-                                * The swap subsystem performs lazy swap slot freeing,
-                                * expecting that the page will be swapped out again.
-                                * So we can avoid an unnecessary write if the page
-                                * isn't redirtied.
-                                * This is good for real swap storage because we can
-                                * reduce unnecessary I/O and enhance wear-leveling
-                                * if an SSD is used as the as swap device.
-                                * But if in-memory swap device (eg zram) is used,
-                                * this causes a duplicated copy between uncompressed
-                                * data in VM-owned memory and compressed data in
-                                * zram-owned memory.  So let's free zram-owned memory
-                                * and make the VM-owned decompressed page *dirty*,
-                                * so the page should be swapped out somewhere again if
-                                * we again wish to reclaim it.
-                                */
-                               struct gendisk *disk = sis->bdev->bd_disk;
-                               if (disk->fops->swap_slot_free_notify) {
-                                       swp_entry_t entry;
-                                       unsigned long offset;
-
-                                       entry.val = page_private(page);
-                                       offset = swp_offset(entry);
-
-                                       SetPageDirty(page);
-                                       disk->fops->swap_slot_free_notify(sis->bdev,
-                                                       offset);
-                               }
+       SetPageUptodate(page);
+
+       /*
+        * There is no guarantee that the page is in swap cache - the software
+        * suspend code (at least) uses end_swap_bio_read() against a non-
+        * swapcache page.  So we must check PG_swapcache before proceeding with
+        * this optimization.
+        */
+       if (likely(PageSwapCache(page))) {
+               struct swap_info_struct *sis;
+
+               sis = page_swap_info(page);
+               if (sis->flags & SWP_BLKDEV) {
+                       /*
+                        * The swap subsystem performs lazy swap slot freeing,
+                        * expecting that the page will be swapped out again.
+                        * So we can avoid an unnecessary write if the page
+                        * isn't redirtied.
+                        * This is good for real swap storage because we can
+                        * reduce unnecessary I/O and enhance wear-leveling
+                        * if an SSD is used as the as swap device.
+                        * But if in-memory swap device (eg zram) is used,
+                        * this causes a duplicated copy between uncompressed
+                        * data in VM-owned memory and compressed data in
+                        * zram-owned memory.  So let's free zram-owned memory
+                        * and make the VM-owned decompressed page *dirty*,
+                        * so the page should be swapped out somewhere again if
+                        * we again wish to reclaim it.
+                        */
+                       struct gendisk *disk = sis->bdev->bd_disk;
+                       if (disk->fops->swap_slot_free_notify) {
+                               swp_entry_t entry;
+                               unsigned long offset;
+
+                               entry.val = page_private(page);
+                               offset = swp_offset(entry);
+
+                               SetPageDirty(page);
+                               disk->fops->swap_slot_free_notify(sis->bdev,
+                                               offset);
                        }
                }
        }
 
+out:
        unlock_page(page);
        bio_put(bio);
 }