From: Darrick J. Wong Date: Wed, 10 Aug 2016 01:36:01 +0000 (+1000) Subject: xfs: increase XFS_BTREE_MAXLEVELS to fit the rmapbt X-Git-Tag: v4.8.0-rc1~80 X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=513ec1c3b683877f00336b31a32e2791dd9674a5;p=thirdparty%2Fxfsprogs-dev.git xfs: increase XFS_BTREE_MAXLEVELS to fit the rmapbt Source kernel commit: df3954ff72590fd20b68261a0c939e40fa3579ea 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 Reviewed-by: Brian Foster Signed-off-by: Dave Chinner --- diff --git a/libxfs/xfs_btree.h b/libxfs/xfs_btree.h index 8fc4ea08b..d1e87b00c 100644 --- a/libxfs/xfs_btree.h +++ b/libxfs/xfs_btree.h @@ -133,7 +133,7 @@ do { \ } \ } while (0) -#define XFS_BTREE_MAXLEVELS 8 /* max of all btrees */ +#define XFS_BTREE_MAXLEVELS 9 /* max of all btrees */ struct xfs_btree_ops { /* size of the key and record structures */