xfs: increase XFS_BTREE_MAXLEVELS to fit the rmapbt
By my calculations, a 1,073,741,824 block AG with a 1k block size can attain a maximum height of 9. Assuming a record size of 24 bytes, a key/ptr size of 44 bytes, and half-full btree nodes, we'd need 53,687,092 blocks for the records and ~6 million blocks for the keys. That requires a btree of height 9 based on the following derivation: Block size = 1024b sblock CRC header = 56b == 1024-56 = 968 bytes for tree data rmapbt record = 24b == 40 records per leaf block rmapbt ptr/key = 44b == 22 ptr/keys per block Worst case, each block is half full, so 20 records and 11 ptrs per block. 1073741824 rmap records / 20 records per block == 53687092 leaf blocks 53687092 leaves / 11 ptrs per block == 4880645 level 1 blocks == 443695 level 2 blocks == 40336 level 3 blocks == 3667 level 4 blocks == 334 level 5 blocks == 31 level 6 blocks == 3 level 7 blocks == 1 level 8 block Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com> Reviewed-by: Brian Foster <bfoster@redhat.com> Signed-off-by: Dave Chinner <david@fromorbit.com>
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@ -133,7 +133,7 @@ do { \
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} \
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} while (0)
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#define XFS_BTREE_MAXLEVELS 8 /* max of all btrees */
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#define XFS_BTREE_MAXLEVELS 9 /* max of all btrees */
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struct xfs_btree_ops {
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/* size of the key and record structures */
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