From ba383eda00b282545ad1da82473a096e3cd71fa3 Mon Sep 17 00:00:00 2001
From: Kevin Atkinson <k@kevina.org>
Date: Wed, 23 Nov 2016 18:00:20 -0500
Subject: [PATCH] "block rm": make channel large enough to avoid blocking

Make the channel for the output of RmBlocks large enough to hold any
result to avoid blocking while holding the GCLock.

License: MIT
Signed-off-by: Kevin Atkinson <k@kevina.org>
---
 blocks/blockstore/util/remove.go | 7 +++++--
 core/commands/block.go           | 5 ++---
 2 files changed, 7 insertions(+), 5 deletions(-)

diff --git a/blocks/blockstore/util/remove.go b/blocks/blockstore/util/remove.go
index 1c8f0c31e9f..b4375855bbf 100644
--- a/blocks/blockstore/util/remove.go
+++ b/blocks/blockstore/util/remove.go
@@ -27,7 +27,10 @@ type RmBlocksOpts struct {
 	Force  bool
 }
 
-func RmBlocks(blocks bs.GCBlockstore, pins pin.Pinner, out chan<- interface{}, cids []*cid.Cid, opts RmBlocksOpts) error {
+func RmBlocks(blocks bs.GCBlockstore, pins pin.Pinner, cids []*cid.Cid, opts RmBlocksOpts) (<-chan interface{}, error) {
+	// make the channel large enough to hold any result to avoid
+	// blocking while holding the GCLock	
+	out := make(chan interface{}, len(cids))
 	go func() {
 		defer close(out)
 
@@ -47,7 +50,7 @@ func RmBlocks(blocks bs.GCBlockstore, pins pin.Pinner, out chan<- interface{}, c
 			}
 		}
 	}()
-	return nil
+	return out, nil
 }
 
 func FilterPinned(pins pin.Pinner, out chan<- interface{}, cids []*cid.Cid) []*cid.Cid {
diff --git a/core/commands/block.go b/core/commands/block.go
index eb96dc06091..fa27b0162ca 100644
--- a/core/commands/block.go
+++ b/core/commands/block.go
@@ -256,8 +256,7 @@ It takes a list of base58 encoded multihashs to remove.
 
 			cids = append(cids, c)
 		}
-		outChan := make(chan interface{})
-		err = util.RmBlocks(n.Blockstore, n.Pinning, outChan, cids, util.RmBlocksOpts{
+		ch, err := util.RmBlocks(n.Blockstore, n.Pinning, cids, util.RmBlocksOpts{
 			Quiet: quiet,
 			Force: force,
 		})
@@ -265,7 +264,7 @@ It takes a list of base58 encoded multihashs to remove.
 			res.SetError(err, cmds.ErrNormal)
 			return
 		}
-		res.SetOutput((<-chan interface{})(outChan))
+		res.SetOutput(ch)
 	},
 	PostRun: func(req cmds.Request, res cmds.Response) {
 		if res.Error() != nil {