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maple_tree: do not preallocate nodes for slot stores 

mas_preallocate() defaults to requesting 1 node for preallocation and then
,depending on the type of store, will update the request variable.  There
isn't a check for a slot store type, so slot stores are preallocating the
default 1 node.  Slot stores do not require any additional nodes, so add a
check for the slot store case that will bypass node_count_gfp().  Update
the tests to reflect that slot stores do not require allocations.

User visible effects of this bug include increased memory usage from the
unneeded node that was allocated.

Link: https://lkml.kernel.org/r/20231213205058.386589-1-sidhartha.kumar@oracle.com
Fixes: 0b8bb544b1 ("maple_tree: update mas_preallocate() testing")
Signed-off-by: Sidhartha Kumar <sidhartha.kumar@oracle.com>
Cc: Liam R. Howlett <Liam.Howlett@oracle.com>
Cc: Matthew Wilcox (Oracle) <willy@infradead.org>
Cc: Peng Zhang <zhangpeng.00@bytedance.com>
Cc: <stable@vger.kernel.org>	[6.6+]
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
This commit is contained in:
Sidhartha Kumar 2023-12-13 12:50:57 -08:00 committed by Andrew Morton
parent e2c27b803b
commit 4249f13c11
2 changed files with 12 additions and 1 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

11
lib/maple_tree.c
View File

@ -5501,6 +5501,17 @@ int mas_preallocate(struct ma_state *mas, void *entry, gfp_t gfp)
mas_wr_end_piv(&wr_mas);
node_size = mas_wr_new_end(&wr_mas);
/* Slot store, does not require additional nodes */
if (node_size == wr_mas.node_end) {
/* reuse node */
if (!mt_in_rcu(mas->tree))
return 0;
/* shifting boundary */
if (wr_mas.offset_end - mas->offset == 1)
return 0;
}
if (node_size >= mt_slots[wr_mas.type]) {
/* Split, worst case for now. */
request = 1 + mas_mt_height(mas) * 2;

2
tools/testing/radix-tree/maple.c
View File

@ -35538,7 +35538,7 @@ static noinline void __init check_prealloc(struct maple_tree *mt)
MT_BUG_ON(mt, mas_preallocate(&mas, ptr, GFP_KERNEL) != 0);
allocated = mas_allocated(&mas);
height = mas_mt_height(&mas);
MT_BUG_ON(mt, allocated != 1);
MT_BUG_ON(mt, allocated != 0);
mas_store_prealloc(&mas, ptr);
MT_BUG_ON(mt, mas_allocated(&mas) != 0);