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>

diff --git a/fs/btrfs/extent_io.c b/fs/btrfs/extent_io.c
index d418164..7d5e556 100644 (file)
--- 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