From 2ef8b1500d26db34a9f76a9bd169f2024213da2e Mon Sep 17 00:00:00 2001
From: Mike Galbraith <mgalbraith@suse.de>
Date: Sun, 2 Nov 2014 08:31:18 +0100
Subject: [PATCH 358/414] fs,btrfs: fix rt deadlock on extent_buffer->lock

Sat Jul 14 12:30:41 CEST 2012

Trivially repeatable deadlock is cured by enabling lockdep code in
btrfs_clear_path_blocking() as suggested by Chris Mason.  He also
suggested restricting blocking reader count to one, and not allowing
a spinning reader while blocking reader exists.  This has proven to
be unnecessary, the strict lock order enforcement is enough.. or
rather that's my box's opinion after long hours of hard pounding.

Note: extent-tree.c bit is additional recommendation from Chris
      Mason, split into a separate patch after discussion.

Link: http://lkml.kernel.org/r/1414913478.5380.114.camel@marge.simpson.net

Cc: linux-rt-users <linux-rt-users@vger.kernel.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Carsten Emde <C.Emde@osadl.org>
Cc: John Kacur <jkacur@redhat.com>
Cc: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Cc: Clark Williams <williams@redhat.com>
Cc: Chris Mason <chris.mason@fusionio.com>
Signed-off-by: Mike Galbraith <efault@gmx.de>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>

Conflicts:
	fs/btrfs/extent-tree.c
---
 fs/btrfs/ctree.c       | 4 ++--
 fs/btrfs/extent-tree.c | 8 --------
 2 files changed, 2 insertions(+), 10 deletions(-)

diff --git a/fs/btrfs/ctree.c b/fs/btrfs/ctree.c
index 56dea84ca2fc..e913cb9888c1 100644
--- a/fs/btrfs/ctree.c
+++ b/fs/btrfs/ctree.c
@@ -81,7 +81,7 @@ noinline void btrfs_clear_path_blocking(struct btrfs_path *p,
 {
 	int i;
 
-#ifdef CONFIG_DEBUG_LOCK_ALLOC
+#if (defined(CONFIG_DEBUG_LOCK_ALLOC) || defined(CONFIG_PREEMPT_RT_BASE))
 	/* lockdep really cares that we take all of these spinlocks
 	 * in the right order.  If any of the locks in the path are not
 	 * currently blocking, it is going to complain.  So, make really
@@ -108,7 +108,7 @@ noinline void btrfs_clear_path_blocking(struct btrfs_path *p,
 		}
 	}
 
-#ifdef CONFIG_DEBUG_LOCK_ALLOC
+#if (defined(CONFIG_DEBUG_LOCK_ALLOC) || defined(CONFIG_PREEMPT_RT_BASE))
 	if (held)
 		btrfs_clear_lock_blocking_rw(held, held_rw);
 #endif
diff --git a/fs/btrfs/extent-tree.c b/fs/btrfs/extent-tree.c
index b3afdde7108c..9ad9c9fa0961 100644
--- a/fs/btrfs/extent-tree.c
+++ b/fs/btrfs/extent-tree.c
@@ -6899,14 +6899,6 @@ again:
 		goto again;
 	}
 
-	if (btrfs_test_opt(root, ENOSPC_DEBUG)) {
-		static DEFINE_RATELIMIT_STATE(_rs,
-				DEFAULT_RATELIMIT_INTERVAL * 10,
-				/*DEFAULT_RATELIMIT_BURST*/ 1);
-		if (__ratelimit(&_rs))
-			WARN(1, KERN_DEBUG
-				"btrfs: block rsv returned %d\n", ret);
-	}
 try_reserve:
 	ret = reserve_metadata_bytes(root, block_rsv, blocksize,
 				     BTRFS_RESERVE_NO_FLUSH);
-- 
2.10.2

