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xfs: introduce refcount btree definitions

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Add new per-AG refcount btree definitions to the per-AG structures.

Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Christoph Hellwig <hch@lst.de>
This commit is contained in:
Darrick J. Wong
2016-10-03 09:11:16 -07:00
parent c75c752d03
commit 46eeb521b9
11 changed files with 93 additions and 10 deletions
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22
fs/xfs/libxfs/xfs_rmap_btree.c
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@@ -512,6 +512,24 @@ void
xfs_rmapbt_compute_maxlevels(
struct xfs_mount *mp)
{
mp->m_rmap_maxlevels = xfs_btree_compute_maxlevels(mp,
mp->m_rmap_mnr, mp->m_sb.sb_agblocks);
/*
* On a non-reflink filesystem, the maximum number of rmap
* records is the number of blocks in the AG, hence the max
* rmapbt height is log_$maxrecs($agblocks). However, with
* reflink each AG block can have up to 2^32 (per the refcount
* record format) owners, which means that theoretically we
* could face up to 2^64 rmap records.
*
* That effectively means that the max rmapbt height must be
* XFS_BTREE_MAXLEVELS. "Fortunately" we'll run out of AG
* blocks to feed the rmapbt long before the rmapbt reaches
* maximum height. The reflink code uses ag_resv_critical to
* disallow reflinking when less than 10% of the per-AG metadata
* block reservation since the fallback is a regular file copy.
*/
if (xfs_sb_version_hasreflink(&mp->m_sb))
mp->m_rmap_maxlevels = XFS_BTREE_MAXLEVELS;
else
mp->m_rmap_maxlevels = xfs_btree_compute_maxlevels(mp,
mp->m_rmap_mnr, mp->m_sb.sb_agblocks);
}