From: Darrick J. Wong <djwong@xxxxxxxxxx> Compute the maximum possible height of the realtime rmap btree when reflink is enabled. Signed-off-by: "Darrick J. Wong" <djwong@xxxxxxxxxx> Reviewed-by: Christoph Hellwig <hch@xxxxxx> --- fs/xfs/libxfs/xfs_rtrmap_btree.c | 28 ++++++++++++++++++++++++++-- 1 file changed, 26 insertions(+), 2 deletions(-) diff --git a/fs/xfs/libxfs/xfs_rtrmap_btree.c b/fs/xfs/libxfs/xfs_rtrmap_btree.c index 3cb8f126b9ce16..04b9c76380adb0 100644 --- a/fs/xfs/libxfs/xfs_rtrmap_btree.c +++ b/fs/xfs/libxfs/xfs_rtrmap_btree.c @@ -718,6 +718,7 @@ xfs_rtrmapbt_maxrecs( unsigned int xfs_rtrmapbt_maxlevels_ondisk(void) { + unsigned long long max_dblocks; unsigned int minrecs[2]; unsigned int blocklen; @@ -726,8 +727,20 @@ xfs_rtrmapbt_maxlevels_ondisk(void) minrecs[0] = xfs_rtrmapbt_block_maxrecs(blocklen, true) / 2; minrecs[1] = xfs_rtrmapbt_block_maxrecs(blocklen, false) / 2; - /* We need at most one record for every block in an rt group. */ - return xfs_btree_compute_maxlevels(minrecs, XFS_MAX_RGBLOCKS); + /* + * Compute the asymptotic maxlevels for an rtrmapbt on any rtreflink fs. + * + * On a reflink filesystem, each block in an rtgroup 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. However, we're + * likely to run out of blocks in the data device long before that + * happens, which means that we must compute the max height based on + * what the btree will look like if it consumes almost all the blocks + * in the data device due to maximal sharing factor. + */ + max_dblocks = -1U; /* max ag count */ + max_dblocks *= XFS_MAX_CRC_AG_BLOCKS; + return xfs_btree_space_to_height(minrecs, max_dblocks); } int __init @@ -766,9 +779,20 @@ xfs_rtrmapbt_compute_maxlevels( * maximum height is constrained by the size of the data device and * the height required to store one rmap record for each block in an * rt group. + * + * On a reflink filesystem, each rt 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. This makes the computation of + * maxlevels based on record count meaningless, so we only consider the + * size of the data device. */ d_maxlevels = xfs_btree_space_to_height(mp->m_rtrmap_mnr, mp->m_sb.sb_dblocks); + if (xfs_has_rtreflink(mp)) { + mp->m_rtrmap_maxlevels = d_maxlevels + 1; + return; + } + r_maxlevels = xfs_btree_compute_maxlevels(mp->m_rtrmap_mnr, mp->m_groups[XG_TYPE_RTG].blocks);