The patch titled Subject: maple_tree: do not preallocate nodes for slot stores has been added to the -mm mm-hotfixes-unstable branch. Its filename is maple_tree-do-not-preallocate-nodes-for-slot-stores.patch
This patch will shortly appear at https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches...
This patch will later appear in the mm-hotfixes-unstable branch at git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm
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------------------------------------------------------ From: Sidhartha Kumar sidhartha.kumar@oracle.com Subject: maple_tree: do not preallocate nodes for slot stores Date: Tue, 12 Dec 2023 11:46:40 -0800
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/20231212194640.217966-1-sidhartha.kumar@oracle.com Fixes: 0b8bb544b1a7 ("maple_tree: update mas_preallocate() testing") Signed-off-by: Sidhartha Kumar sidhartha.kumar@oracle.com Reviewed-by: 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 Signed-off-by: Andrew Morton akpm@linux-foundation.org ---
lib/maple_tree.c | 6 ++++++ tools/testing/radix-tree/maple.c | 2 +- 2 files changed, 7 insertions(+), 1 deletion(-)
--- a/lib/maple_tree.c~maple_tree-do-not-preallocate-nodes-for-slot-stores +++ a/lib/maple_tree.c @@ -5501,6 +5501,12 @@ int mas_preallocate(struct ma_state *mas
mas_wr_end_piv(&wr_mas); node_size = mas_wr_new_end(&wr_mas); + + /* Slot store, does not require additional nodes */ + if ((node_size == mas->end) && ((!mt_in_rcu(mas->tree)) + || (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; --- a/tools/testing/radix-tree/maple.c~maple_tree-do-not-preallocate-nodes-for-slot-stores +++ a/tools/testing/radix-tree/maple.c @@ -35538,7 +35538,7 @@ static noinline void __init check_preall 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);
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Patches currently in -mm which might be from sidhartha.kumar@oracle.com are
maple_tree-do-not-preallocate-nodes-for-slot-stores.patch