Btrfs: be more polite in the async caching threads

The semaphore used by the async caching threads can prevent a
transaction commit, which can make the FS appear to stall.  This
releases the semaphore more often when a transaction commit is
in progress.

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

1 files changed, 10 insertions, 0 deletions

diff --git a/fs/btrfs/transaction.c b/fs/btrfs/transaction.c
index de48e4ec808c..cdbb5022da52 100644
--- a/fs/btrfs/transaction.c
+++ b/fs/btrfs/transaction.c
@@ -857,6 +857,16 @@ static void update_super_roots(struct btrfs_root *root)
         super->root_level = root_item->level;
 }
 
+int btrfs_transaction_in_commit(struct btrfs_fs_info *info)
+{
+        int ret = 0;
+        spin_lock(&info->new_trans_lock);
+        if (info->running_transaction)
+                ret = info->running_transaction->in_commit;
+        spin_unlock(&info->new_trans_lock);
+        return ret;
+}
+
 int btrfs_commit_transaction(struct btrfs_trans_handle *trans,
                              struct btrfs_root *root)
 {