btrfs: Add handler for invalidate page

For btrfs_invalidatepage() and its variant evict_inode_truncate_page(),
there will be pages don't reach disk.
In that case, their reserved space won't be release nor freed by
finish_ordered_io() nor delayed_ref handler.

So we must free their qgroup reserved space, or we will leaking reserved
space again.

So this will patch will call btrfs_qgroup_free_data() for
invalidatepage() and its variant evict_inode_truncate_page().

And due to the nature of new btrfs_qgroup_reserve/free_data() reserved
space will only be reserved or freed once, so for pages which are
already flushed to disk, their reserved space will be released and freed
by delayed_ref handler.

Double free won't be a problem.

Signed-off-by: Qu Wenruo <quwenruo@cn.fujitsu.com>
Signed-off-by: Chris Mason <clm@fb.com>

1 files changed, 24 insertions, 0 deletions

diff --git a/fs/btrfs/inode.c b/fs/btrfs/inode.c
index ef5d3694b944..6670792704e8 100644
--- a/fs/btrfs/inode.c
+++ b/fs/btrfs/inode.c
@@ -5132,6 +5132,18 @@ static void evict_inode_truncate_pages(struct inode *inode)
                 spin_unlock(&io_tree->lock);
 
                 lock_extent_bits(io_tree, start, end, 0, &cached_state);
+
+                /*
+                 * If still has DELALLOC flag, the extent didn't reach disk,
+                 * and its reserved space won't be freed by delayed_ref.
+                 * So we need to free its reserved space here.
+                 * (Refer to comment in btrfs_invalidatepage, case 2)
+                 *
+                 * Note, end is the bytenr of last byte, so we need + 1 here.
+                 */
+                if (state->state & EXTENT_DELALLOC)
+                        btrfs_qgroup_free_data(inode, start, end - start + 1);
+
                 clear_extent_bit(io_tree, start, end,
                                  EXTENT_LOCKED | EXTENT_DIRTY |
                                  EXTENT_DELALLOC | EXTENT_DO_ACCOUNTING |
@@ -8646,6 +8658,18 @@ static void btrfs_invalidatepage(struct page *page, unsigned int offset,
                 }
         }
 
+        /*
+         * Qgroup reserved space handler
+         * Page here will be either
+         * 1) Already written to disk
+         *    In this case, its reserved space is released from data rsv map
+         *    and will be freed by delayed_ref handler finally.
+         *    So even we call qgroup_free_data(), it won't decrease reserved
+         *    space.
+         * 2) Not written to disk
+         *    This means the reserved space should be freed here.
+         */
+        btrfs_qgroup_free_data(inode, page_start, PAGE_CACHE_SIZE);
         if (!inode_evicting) {
                 clear_extent_bit(tree, page_start, page_end,
                                  EXTENT_LOCKED | EXTENT_DIRTY |