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xfs: compute rtrmap btree max levels when reflink enabled

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Compute the maximum possible height of the realtime rmap btree when
reflink is enabled.

Signed-off-by: "Darrick J. Wong" <djwong@kernel.org>
Reviewed-by: Christoph Hellwig <hch@lst.de>
This commit is contained in:
Darrick J. Wong
2024-11-20 16:20:57 -08:00
parent 0bada82331
commit c2694ff678
1 changed files with 26 additions and 2 deletions
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28
fs/xfs/libxfs/xfs_rtrmap_btree.c
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@@ -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);