reflink log reservations

[Christoph Hellwig]

On Thu, Feb 04, 2016 at 12:16:20AM -0800, Darrick J. Wong wrote:
> On Thu, Feb 04, 2016 at 08:46:17AM +0100, Christoph Hellwig wrote:
> > Hi Darrick,
> > 
> > I'm running into the following log reservation assert after a few
> > xfstests runs over NFS.  I'll try to understand the reservation
> > calculations, but in case this is still fresh in your head here's
> > a headsup:
> 
> Hmm, interesting, I haven't seen /that/ one... my guess is that the
> block reservation needs to be bumped up for the refcount tree.

This seems to fix it for me:

---
>From 6e27eb42ece3a25f610690487b403a0091cafa26 Mon Sep 17 00:00:00 2001
From: Christoph Hellwig <hch at lst.de>
Date: Thu, 4 Feb 2016 13:50:16 +0100
Subject: xfs: account for the refcount btree in the alloc/free log reservation

Signed-off-by: Christoph Hellwig <hch at lst.de>
---
 fs/xfs/libxfs/xfs_trans_resv.c | 15 ++++++++++-----
 1 file changed, 10 insertions(+), 5 deletions(-)

diff --git a/fs/xfs/libxfs/xfs_trans_resv.c b/fs/xfs/libxfs/xfs_trans_resv.c
index d495f82..f4c2648 100644
--- a/fs/xfs/libxfs/xfs_trans_resv.c
+++ b/fs/xfs/libxfs/xfs_trans_resv.c
@@ -65,12 +65,15 @@ xfs_calc_buf_res(
 
 /*
  * Per-extent log reservation for the allocation btree changes
- * involved in freeing or allocating an extent. When rmap is not enabled,
- * there are only two trees that will be modified (free space trees), and when
- * rmap is enabled there will be three (freespace + rmap trees). The number of
- * blocks reserved is based on the formula:
+ * involved in freeing or allocating an extent.
  *
- * num trees * ((2 blocks/level * max depth) - 1)
+ * There are at least two trees that will be modified (free space trees), when
+ * rmap is enabled there will be an additional rmap tree, and when reflinks
+ * are enabled there will be a refcount btree as well
+ *
+ * The number of  blocks reserved is based on the formula:
+ *
+ *     num trees * ((2 blocks/level * max depth) - 1)
  */
 static uint
 xfs_allocfree_log_count(
@@ -81,6 +84,8 @@ xfs_allocfree_log_count(
 
 	if (xfs_sb_version_hasrmapbt(&mp->m_sb))
 		num_trees++;
+	if (xfs_sb_version_hasreflink(&mp->m_sb))
+		num_trees++;
 
 	return num_ops * num_trees * (2 * mp->m_ag_maxlevels - 1);
 }
-- 
2.1.4