[PATCH 07/20] xfs: rmap btree add more reserved blocks

[Dave Chinner <david@fromorbit.com>]

From: Dave Chinner <dchinner@redhat.com>

XFS reserves a small amount of space in each AG for the minimum
number of free blocks needed for operation. Adding the rmap btree
increases the number of reserved blocks, but it also increases the
complexity of the calculation as the free inode btree is optional
(like the rmbt).

Rather than calculate the prealloc blocks every time we need to
check it, add a function to calculate it at mount time and store it
in the struct xfs_mount, and convert the XFS_PREALLOC_BLOCKS macro
just to use the xfs-mount variable directly.

Signed-off-by: Dave Chinner <dchinner@redhat.com>
---
 fs/xfs/libxfs/xfs_alloc.c  | 11 +++++++++++
 fs/xfs/libxfs/xfs_alloc.h  |  2 ++
 fs/xfs/libxfs/xfs_format.h |  9 +--------
 fs/xfs/xfs_fsops.c         |  6 +++---
 fs/xfs/xfs_mount.c         |  2 ++
 fs/xfs/xfs_mount.h         |  1 +
 6 files changed, 20 insertions(+), 11 deletions(-)

diff --git a/fs/xfs/libxfs/xfs_alloc.c b/fs/xfs/libxfs/xfs_alloc.c
index c7206b5..a683d7a 100644
--- a/fs/xfs/libxfs/xfs_alloc.c
+++ b/fs/xfs/libxfs/xfs_alloc.c
@@ -49,6 +49,17 @@ STATIC int xfs_alloc_ag_vextent_size(xfs_alloc_arg_t *);
 STATIC int xfs_alloc_ag_vextent_small(xfs_alloc_arg_t *,
 		xfs_btree_cur_t *, xfs_agblock_t *, xfs_extlen_t *, int *);
 
+xfs_extlen_t
+xfs_prealloc_blocks(
+	struct xfs_mount	*mp)
+{
+	if (xfs_sb_version_hasrmapbt(&mp->m_sb))
+		return XFS_RMAP_BLOCK(mp) + 1;
+	if (xfs_sb_version_hasfinobt(&mp->m_sb))
+		return XFS_FIBT_BLOCK(mp) + 1;
+	return XFS_IBT_BLOCK(mp) + 1;
+}
+
 /*
  * Lookup the record equal to [bno, len] in the btree given by cur.
  */
diff --git a/fs/xfs/libxfs/xfs_alloc.h b/fs/xfs/libxfs/xfs_alloc.h
index ca1c816..71379f6 100644
--- a/fs/xfs/libxfs/xfs_alloc.h
+++ b/fs/xfs/libxfs/xfs_alloc.h
@@ -234,4 +234,6 @@ xfs_alloc_get_rec(
 int xfs_read_agf(struct xfs_mount *mp, struct xfs_trans *tp,
 			xfs_agnumber_t agno, int flags, struct xfs_buf **bpp);
 
+xfs_extlen_t xfs_prealloc_blocks(struct xfs_mount *mp);
+
 #endif	/* __XFS_ALLOC_H__ */
diff --git a/fs/xfs/libxfs/xfs_format.h b/fs/xfs/libxfs/xfs_format.h
index d120af4..e81ffec 100644
--- a/fs/xfs/libxfs/xfs_format.h
+++ b/fs/xfs/libxfs/xfs_format.h
@@ -1288,18 +1288,11 @@ typedef __be32 xfs_inobt_ptr_t;
  */
 #define	XFS_RMAP_CRC_MAGIC	0x524d4233	/* 'RMB3' */
 
-/*
- * The first data block of an AG depends on whether the filesystem was formatted
- * with the finobt feature. If so, account for the finobt reserved root btree
- * block.
- */
-#define XFS_PREALLOC_BLOCKS(mp) \
+#define	XFS_RMAP_BLOCK(mp) \
 	(xfs_sb_version_hasfinobt(&((mp)->m_sb)) ? \
 	 XFS_FIBT_BLOCK(mp) + 1 : \
 	 XFS_IBT_BLOCK(mp) + 1)
 
-
-
 /*
  * BMAP Btree format definitions
  *
diff --git a/fs/xfs/xfs_fsops.c b/fs/xfs/xfs_fsops.c
index 4bd6463..a564c4c 100644
--- a/fs/xfs/xfs_fsops.c
+++ b/fs/xfs/xfs_fsops.c
@@ -246,7 +246,7 @@ xfs_growfs_data_private(
 		agf->agf_flfirst = 0;
 		agf->agf_fllast = cpu_to_be32(XFS_AGFL_SIZE(mp) - 1);
 		agf->agf_flcount = 0;
-		tmpsize = agsize - XFS_PREALLOC_BLOCKS(mp);
+		tmpsize = agsize - mp->m_ag_prealloc_blocks;
 		agf->agf_freeblks = cpu_to_be32(tmpsize);
 		agf->agf_longest = cpu_to_be32(tmpsize);
 		if (xfs_sb_version_hascrc(&mp->m_sb))
@@ -343,7 +343,7 @@ xfs_growfs_data_private(
 						agno, 0);
 
 		arec = XFS_ALLOC_REC_ADDR(mp, XFS_BUF_TO_BLOCK(bp), 1);
-		arec->ar_startblock = cpu_to_be32(XFS_PREALLOC_BLOCKS(mp));
+		arec->ar_startblock = cpu_to_be32(mp->m_ag_prealloc_blocks);
 		arec->ar_blockcount = cpu_to_be32(
 			agsize - be32_to_cpu(arec->ar_startblock));
 
@@ -372,7 +372,7 @@ xfs_growfs_data_private(
 						agno, 0);
 
 		arec = XFS_ALLOC_REC_ADDR(mp, XFS_BUF_TO_BLOCK(bp), 1);
-		arec->ar_startblock = cpu_to_be32(XFS_PREALLOC_BLOCKS(mp));
+		arec->ar_startblock = cpu_to_be32(mp->m_ag_prealloc_blocks);
 		arec->ar_blockcount = cpu_to_be32(
 			agsize - be32_to_cpu(arec->ar_startblock));
 		nfree += be32_to_cpu(arec->ar_blockcount);
diff --git a/fs/xfs/xfs_mount.c b/fs/xfs/xfs_mount.c
index 461e791..9d6be55 100644
--- a/fs/xfs/xfs_mount.c
+++ b/fs/xfs/xfs_mount.c
@@ -239,6 +239,8 @@ xfs_initialize_perag(
 
 	if (maxagi)
 		*maxagi = index;
+
+	mp->m_ag_prealloc_blocks = xfs_prealloc_blocks(mp);
 	return 0;
 
 out_unwind:
diff --git a/fs/xfs/xfs_mount.h b/fs/xfs/xfs_mount.h
index 7999e91..d9c9834 100644
--- a/fs/xfs/xfs_mount.h
+++ b/fs/xfs/xfs_mount.h
@@ -93,6 +93,7 @@ typedef struct xfs_mount {
 	uint			m_ag_maxlevels;	/* XFS_AG_MAXLEVELS */
 	uint			m_bm_maxlevels[2]; /* XFS_BM_MAXLEVELS */
 	uint			m_in_maxlevels;	/* max inobt btree levels. */
+	xfs_extlen_t		m_ag_prealloc_blocks; /* reserved ag blocks */
 	struct radix_tree_root	m_perag_tree;	/* per-ag accounting info */
 	spinlock_t		m_perag_lock;	/* lock for m_perag_tree */
 	struct mutex		m_growlock;	/* growfs mutex */
-- 
2.0.0

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