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>

1 files changed, 26 insertions, 25 deletions

diff --git a/fs/btrfs/extent_io.c b/fs/btrfs/extent_io.c
index ea100eb188de..43af5a61ad25 100644
--- 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);
 }