Btrfs: Throttle operations if the reference cache gets too large

A large reference cache is directly related to a lot of work pending
for the cleaner thread.  This throttles back new operations based on
the size of the reference cache so the cleaner thread will be able to keep
up.

Overall, this actually makes the FS faster because the cleaner thread will
be more likely to find things in cache.

Signed-off-by: Chris Mason <chris.mason@oracle.com>

1 files changed, 1 insertions, 0 deletions

diff --git a/fs/btrfs/file.c b/fs/btrfs/file.c
index 3efec25e34b0..ded5281f8463 100644
--- a/fs/btrfs/file.c
+++ b/fs/btrfs/file.c
@@ -974,6 +974,7 @@ static ssize_t btrfs_file_write(struct file *file, const char __user *buf,
                 balance_dirty_pages_ratelimited_nr(inode->i_mapping, num_pages);
                 if (num_pages < (root->leafsize >> PAGE_CACHE_SHIFT) + 1)
                         btrfs_btree_balance_dirty(root, 1);
+                btrfs_throttle(root);
                 cond_resched();
         }
 out: