Btrfs: fix btrfs_release_extent_buffer_page with the right usage of num_extent_pages

num_extent_pages returns the number of pages in the specific range, not
the index of the last page in the eb range.

btrfs_release_extent_buffer_page is called with start_idx set 0 in current
codes, so it's not a problem yet. But the logic is indeed wrong.

Fix it here.

Signed-off-by: Wang Sheng-Hui <shhuiw@gmail.com>

diff --git a/fs/btrfs/extent_io.c b/fs/btrfs/extent_io.c
index aeb98ce..455daec 100644 (file)
--- a/fs/btrfs/extent_io.c
+++ b/fs/btrfs/extent_io.c
@@ -3981,11 +3981,13 @@ static void btrfs_release_extent_buffer_page(struct extent_buffer *eb,
                                                unsigned long start_idx)
 {
        unsigned long index;
+       unsigned long num_pages;
        struct page *page;
 
        BUG_ON(extent_buffer_under_io(eb));
 
-       index = num_extent_pages(eb->start, eb->len);
+       num_pages = num_extent_pages(eb->start, eb->len);
+       index = start_idx + num_pages;
        if (start_idx >= index)
                return;