Btrfs: btrfs_release_extent_buffer_page didn't free pages of dummy extent

btrfs_release_extent_buffer_page() can't handle dummy extent that
allocated by btrfs_clone_extent_buffer() properly. That is because
reference count of pages that allocated by btrfs_clone_extent_buffer()
was 2, 1 by alloc_page(), and another by attach_extent_buffer_page().

Running following command repeatly can check this memory leak problem

    btrfs inspect-internal inode-resolve 256 /mnt/btrfs

Signed-off-by: Chien-Kuan Yeh <ckya@synology.com>
Signed-off-by: Forrest Liu <forrestl@synology.com>
Reviewed-by: Filipe Manana <fdmanana@suse.com>
Tested-by: Filipe Manana <fdmanana@suse.com>
Signed-off-by: Chris Mason <clm@fb.com>

diff --git a/fs/btrfs/extent_io.c b/fs/btrfs/extent_io.c
index ea100eb..43af5a6 100644 (file)
--- a/fs/btrfs/extent_io.c
+++ b/fs/btrfs/extent_io.c
@@ -4560,36 +4560,37 @@ static void btrfs_release_extent_buffer_page(struct extent_buffer *eb)
        do {
                index--;
                page = eb->pages[index];
-               if (page && mapped) {
+               if (!page)
+                       continue;
+               if (mapped)
                        spin_lock(&page->mapping->private_lock);
+               /*
+                * We do this since we'll remove the pages after we've
+                * removed the eb from the radix tree, so we could race
+                * and have this page now attached to the new eb.  So
+                * only clear page_private if it's still connected to
+                * this eb.
+                */
+               if (PagePrivate(page) &&
+                   page->private == (unsigned long)eb) {
+                       BUG_ON(test_bit(EXTENT_BUFFER_DIRTY, &eb->bflags));
+                       BUG_ON(PageDirty(page));
+                       BUG_ON(PageWriteback(page));
                        /*
-                        * We do this since we'll remove the pages after we've
-                        * removed the eb from the radix tree, so we could race
-                        * and have this page now attached to the new eb.  So
-                        * only clear page_private if it's still connected to
-                        * this eb.
+                        * We need to make sure we haven't be attached
+                        * to a new eb.
                         */
-                       if (PagePrivate(page) &&
-                           page->private == (unsigned long)eb) {
-                               BUG_ON(test_bit(EXTENT_BUFFER_DIRTY, &eb->bflags));
-                               BUG_ON(PageDirty(page));
-                               BUG_ON(PageWriteback(page));
-                               /*
-                                * We need to make sure we haven't be attached
-                                * to a new eb.
-                                */
-                               ClearPagePrivate(page);
-                               set_page_private(page, 0);
-                               /* One for the page private */
-                               page_cache_release(page);
-                       }
-                       spin_unlock(&page->mapping->private_lock);
-
-               }
-               if (page) {
-                       /* One for when we alloced the page */
+                       ClearPagePrivate(page);
+                       set_page_private(page, 0);
+                       /* One for the page private */
                        page_cache_release(page);
                }
+
+               if (mapped)
+                       spin_unlock(&page->mapping->private_lock);
+
+               /* One for when we alloced the page */
+               page_cache_release(page);
        } while (index != 0);
 }