[PATCH] Btrfs: force delalloc flushing when things get desperate

[Josef Bacik <josef@redhat.com>]

When testing with max_extents=4k, we enospc out really really early.  The reason
for this is we really overwhelm the system with our worst case calculation.
When we try to flush delalloc, we don't want everybody to wait around forever,
so we wake up the waiters when we've done some of the work in hopes that its
enough work to get everything they need done.  The problem with this is we don't
wait long enough sometimes.  So if we've already done a flush_delalloc and
didn't find what we need, do it again and this time wait for the flushing to be
completely finished before returning.  This makes my ENOSPC test actually
finish, instead of finishing in about 20 seconds.  Thanks,

Signed-off-by: Josef Bacik <josef@redhat.com>
---
 fs/btrfs/extent-tree.c |   25 +++++++++++++++++--------
 1 files changed, 17 insertions(+), 8 deletions(-)

diff --git a/fs/btrfs/extent-tree.c b/fs/btrfs/extent-tree.c
index 0085dcb..aeef481 100644
--- a/fs/btrfs/extent-tree.c
+++ b/fs/btrfs/extent-tree.c
@@ -2873,7 +2873,7 @@ static noinline void flush_delalloc_async(struct btrfs_work *work)
 	kfree(async);
 }
 
-static void wait_on_flush(struct btrfs_root *root, struct btrfs_space_info *info)
+static void wait_on_flush(struct btrfs_root *root, struct btrfs_space_info *info, int soft)
 {
 	DEFINE_WAIT(wait);
 	u64 num_bytes;
@@ -2895,6 +2895,12 @@ static void wait_on_flush(struct btrfs_root *root, struct btrfs_space_info *info
 			break;
 		}
 
+		if (!soft) {
+			spin_unlock(&info->lock);
+			schedule();
+			continue;
+		}
+
 		free = 0;
 		for_each_possible_cpu(i) {
 			struct btrfs_reserved_space_pool *pool;
@@ -2924,7 +2930,7 @@ static void wait_on_flush(struct btrfs_root *root, struct btrfs_space_info *info
 }
 
 static void flush_delalloc(struct btrfs_root *root,
-				 struct btrfs_space_info *info)
+			   struct btrfs_space_info *info, int soft)
 {
 	struct async_flush *async;
 	bool wait = false;
@@ -2939,7 +2945,7 @@ static void flush_delalloc(struct btrfs_root *root,
 	spin_unlock(&info->lock);
 
 	if (wait) {
-		wait_on_flush(root, info);
+		wait_on_flush(root, info, soft);
 		return;
 	}
 
@@ -2953,7 +2959,7 @@ static void flush_delalloc(struct btrfs_root *root,
 
 	btrfs_queue_worker(&root->fs_info->enospc_workers,
 			   &async->work);
-	wait_on_flush(root, info);
+	wait_on_flush(root, info, soft);
 	return;
 
 flush:
@@ -3146,14 +3152,17 @@ again:
 
 	if (!delalloc_flushed) {
 		delalloc_flushed = true;
-		flush_delalloc(root, meta_sinfo);
+		flush_delalloc(root, meta_sinfo, 1);
 		goto again;
 	}
 
 	if (!chunk_allocated) {
+		int ret;
+
 		chunk_allocated = true;
-		btrfs_wait_ordered_extents(root, 0, 0);
-		maybe_allocate_chunk(root, meta_sinfo);
+		ret = maybe_allocate_chunk(root, meta_sinfo);
+		if (!ret)
+			flush_delalloc(root, meta_sinfo, 0);
 		goto again;
 	}
 
@@ -3338,7 +3347,7 @@ again:
 
 	if (!delalloc_flushed) {
 		delalloc_flushed = true;
-		flush_delalloc(root, meta_sinfo);
+		flush_delalloc(root, meta_sinfo, 0);
 		goto again;
 	}
 
-- 
1.6.6