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maple_tree: break on convergence in mas_spanning_rebalance()

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This allows support for using the vacant height to calculate the worst
case number of nodes needed for wr_rebalance operation. 
mas_spanning_rebalance() was seen to perform unnecessary node allocations.
We can reduce allocations by breaking early during the rebalancing loop
once we realize that we have ascended to a common ancestor.

Link: https://lkml.kernel.org/r/20250410191446.2474640-5-sidhartha.kumar@oracle.com
Signed-off-by: Sidhartha Kumar <sidhartha.kumar@oracle.com>
Suggested-by: Liam Howlett <liam.howlett@oracle.com>
Reviewed-by: Wei Yang <richard.weiyang@gmail.com>
Reviewed-by: Liam R. Howlett <Liam.Howlett@Oracle.com>
Cc: Matthew Wilcox (Oracle) <willy@infradead.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
This commit is contained in:
Sidhartha Kumar 2025-04-10 19:14:44 +00:00 • committed by Andrew Morton
parent ad88fc17d2
commit 300a5b4ffe
1 changed files with 13 additions and 3 deletions
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16
lib/maple_tree.c
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@ -2893,11 +2893,21 @@ static void mas_spanning_rebalance(struct ma_state *mas,
mast_combine_cp_right(mast);
mast->orig_l->last = mast->orig_l->max;
if (mast_sufficient(mast))
continue;
if (mast_sufficient(mast)) {
if (mast_overflow(mast))
continue;
if (mast->orig_l->node == mast->orig_r->node) {
/*
* The data in b_node should be stored in one
* node and in the tree
*/
slot = mast->l->offset;
break;
}
if (mast_overflow(mast))
continue;
}
/* May be a new root stored in mast->bn */
if (mas_is_root_limits(mast->orig_l))