[PATCH 17/71] xfs: refcount btree requires more reserved space

The reference count btree is allocated from the free space, which
means that we have to ensure that an AG can't run out of free space
while performing a refcount operation.  In the pathological case each
AG block has its own refcntbt record, so we have to keep that much
space available.

v2: Calculate the maximum possible size of the rmap and refcount
btrees based on minimally-full btree blocks.  This increases the
per-AG block reservations to handle the worst case btree size.

Signed-off-by: Darrick J. Wong <[email protected]>
---
 libxfs/xfs_alloc.c          |    3 +++
 libxfs/xfs_refcount_btree.c |   23 +++++++++++++++++++++++
 libxfs/xfs_refcount_btree.h |    4 ++++
 3 files changed, 30 insertions(+)


diff --git a/libxfs/xfs_alloc.c b/libxfs/xfs_alloc.c
index e754647..3151fbb 100644
--- a/libxfs/xfs_alloc.c
+++ b/libxfs/xfs_alloc.c
@@ -34,6 +34,7 @@
 #include "xfs_trace.h"
 #include "xfs_trans.h"
 #include "xfs_ag_resv.h"
+#include "xfs_refcount_btree.h"
 
 struct workqueue_struct *xfs_alloc_wq;
 
@@ -124,6 +125,8 @@ xfs_alloc_ag_max_usable(
 		blocks++;		/* finobt root block */
 	if (xfs_sb_version_hasrmapbt(&mp->m_sb))
 		blocks++; 		/* rmap root block */
+	if (xfs_sb_version_hasreflink(&mp->m_sb))
+		blocks++;		/* refcount root block */
 
 	return mp->m_sb.sb_agblocks - blocks;
 }
diff --git a/libxfs/xfs_refcount_btree.c b/libxfs/xfs_refcount_btree.c
index 04f8db0..568a2f8 100644
--- a/libxfs/xfs_refcount_btree.c
+++ b/libxfs/xfs_refcount_btree.c
@@ -380,3 +380,26 @@ xfs_refcountbt_compute_maxlevels(
 	mp->m_refc_maxlevels = xfs_btree_compute_maxlevels(mp,
 			mp->m_refc_mnr, mp->m_sb.sb_agblocks);
 }
+
+/* Calculate the refcount btree size for some records. */
+xfs_extlen_t
+xfs_refcountbt_calc_size(
+	struct xfs_mount	*mp,
+	unsigned long long	len)
+{
+	return xfs_btree_calc_size(mp, mp->m_refc_mnr, len);
+}
+
+/*
+ * Calculate the maximum refcount btree size.
+ */
+xfs_extlen_t
+xfs_refcountbt_max_size(
+	struct xfs_mount	*mp)
+{
+	/* Bail out if we're uninitialized, which can happen in mkfs. */
+	if (mp->m_refc_mxr[0] == 0)
+		return 0;
+
+	return xfs_refcountbt_calc_size(mp, mp->m_sb.sb_agblocks);
+}
diff --git a/libxfs/xfs_refcount_btree.h b/libxfs/xfs_refcount_btree.h
index 9e9ad7c..780b02f 100644
--- a/libxfs/xfs_refcount_btree.h
+++ b/libxfs/xfs_refcount_btree.h
@@ -64,4 +64,8 @@ extern int xfs_refcountbt_maxrecs(struct xfs_mount *mp, int blocklen,
 		bool leaf);
 extern void xfs_refcountbt_compute_maxlevels(struct xfs_mount *mp);
 
+extern xfs_extlen_t xfs_refcountbt_calc_size(struct xfs_mount *mp,
+		unsigned long long len);
+extern xfs_extlen_t xfs_refcountbt_max_size(struct xfs_mount *mp);
+
 #endif	/* __XFS_REFCOUNT_BTREE_H__ */

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