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xfs: create a standard btree size calculator code

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Create a helper to generate AG btree height calculator functions.
This will be used (much) later when we get to the refcount btree.

Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Dave Chinner <david@fromorbit.com>
This commit is contained in:
Darrick J. Wong 2016-09-19 10:25:03 +10:00 committed by Dave Chinner
parent a1d46cffaf
commit 4ed3f68792
2 changed files with 26 additions and 0 deletions
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24
fs/xfs/libxfs/xfs_btree.c
View file

@ -4797,3 +4797,27 @@ xfs_btree_query_range(
return xfs_btree_overlapped_query_range(cur, &low_key, &high_key,
fn, priv);
}
/*
* Calculate the number of blocks needed to store a given number of records
* in a short-format (per-AG metadata) btree.
*/
xfs_extlen_t
xfs_btree_calc_size(
struct xfs_mount *mp,
uint *limits,
unsigned long long len)
{
int level;
int maxrecs;
xfs_extlen_t rval;
maxrecs = limits[0];
for (level = 0, rval = 0; len > 1; level++) {
len += maxrecs - 1;
do_div(len, maxrecs);
maxrecs = limits[1];
rval += len;
}
return rval;
}

2
fs/xfs/libxfs/xfs_btree.h
View file

@ -501,6 +501,8 @@ bool xfs_btree_sblock_v5hdr_verify(struct xfs_buf *bp);
bool xfs_btree_sblock_verify(struct xfs_buf *bp, unsigned int max_recs);
uint xfs_btree_compute_maxlevels(struct xfs_mount *mp, uint *limits,
unsigned long len);
xfs_extlen_t xfs_btree_calc_size(struct xfs_mount *mp, uint *limits,
unsigned long long len);
/* return codes */
#define XFS_BTREE_QUERY_RANGE_CONTINUE 0 /* keep iterating */