Btrfs: skip looking for delalloc if we don't have ->fill_delalloc

We always look for delalloc bytes in our io_tree so we can fill in delalloc.
This is fine in most cases, but if we're writing out the btree_inode this is
just a superfluous tree search on the io_tree, and if we have a lot of metadata
dirty this could be an expensive check.  So instead check to see if our io_tree
has a ->fill_delalloc op, and if not don't even bother doing the lookup.
Thanks,

Signed-off-by: Josef Bacik <josef@redhat.com>

1 files changed, 5 insertions, 1 deletions

diff --git a/fs/btrfs/extent_io.c b/fs/btrfs/extent_io.c
index d418164a35f1..7d5e55632809 100644
--- a/fs/btrfs/extent_io.c
+++ b/fs/btrfs/extent_io.c
@@ -2136,6 +2136,7 @@ static int __extent_writepage(struct page *page, struct writeback_control *wbc,
         int compressed;
         int write_flags;
         unsigned long nr_written = 0;
+        bool fill_delalloc = true;
 
         if (wbc->sync_mode == WB_SYNC_ALL)
                 write_flags = WRITE_SYNC;
@@ -2166,10 +2167,13 @@ static int __extent_writepage(struct page *page, struct writeback_control *wbc,
 
         set_page_extent_mapped(page);
 
+        if (!tree->ops || !tree->ops->fill_delalloc)
+                fill_delalloc = false;
+
         delalloc_start = start;
         delalloc_end = 0;
         page_started = 0;
-        if (!epd->extent_locked) {
+        if (!epd->extent_locked && fill_delalloc) {
                 u64 delalloc_to_write = 0;
                 /*
                  * make sure the wbc mapping index is at least updated