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>

3 files changed, 14 insertions, 2 deletions

diff --git a/fs/btrfs/extent-tree.c b/fs/btrfs/extent-tree.c
index 2fe21fa74913..dc84daee6bc4 100644
--- a/fs/btrfs/extent-tree.c
+++ b/fs/btrfs/extent-tree.c
@@ -302,10 +302,11 @@ again:
                         else if (ret)
                                 break;
 
-                        if (need_resched()) {
+                        if (need_resched() ||
+                            btrfs_transaction_in_commit(fs_info)) {
                                 btrfs_release_path(fs_info->extent_root, path);
                                 up_read(&fs_info->extent_commit_sem);
-                                cond_resched();
+                                schedule_timeout(1);
                                 goto again;
                         }
 
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)
 {
diff --git a/fs/btrfs/transaction.h b/fs/btrfs/transaction.h
index 961c3ee5a2e1..663c67404918 100644
--- a/fs/btrfs/transaction.h
+++ b/fs/btrfs/transaction.h
@@ -107,4 +107,5 @@ int btrfs_record_root_in_trans(struct btrfs_trans_handle *trans,
                                 struct btrfs_root *root);
 int btrfs_write_and_wait_marked_extents(struct btrfs_root *root,
                                         struct extent_io_tree *dirty_pages);
+int btrfs_transaction_in_commit(struct btrfs_fs_info *info);
 #endif