From 83d97f620f611ab3fbf2de585bf34bd9dab513c2 Mon Sep 17 00:00:00 2001 From: "Liam R. Howlett" Date: Fri, 4 Aug 2023 12:59:46 -0400 Subject: [PATCH] maple_tree: add hex output to maple_arange64 dump Patch series "maple_tree: Change replacement strategy". The maple tree marks nodes dead as soon as they are going to be replaced. This could be problematic when used in the RCU context since the writer may be starved of CPU time by the readers. This patch set addresses the issue by switching the data replacement strategy to one that will only mark data as dead once the new data is available. This series changes the ordering of the node replacement so that the new data is live before the old data is marked 'dead'. When readers hit 'dead' nodes, they will restart from the top of the tree and end up in the new data. In more complex scenarios, the replacement strategy means a subtree is built and graphed into the tree leaving some nodes to point to the old parent. The view of tasks into the old data will either remain with the old data, or see the new data once the old data is marked 'dead'. Iterators will see the 'dead' node and restart on their own and switch to the new data. There is no risk of the reader seeing old data in these cases. The 'dead' subtree of data is then fully marked dead, but reused nodes will still point to the dead nodes until the parent pointer is updated. Walking up to a 'dead' node will cause a re-walk from the top of the tree and enter the new data area where old data is not reachable. Once the parent pointers are fully up to date in the active data, the 'dead' subtree is iterated to collect entirely 'dead' subtrees, and dead nodes (nodes that partially contained reused data). This patch (of 6): When dumping the tree, honour formatting request to output hex for the maple node type arange64. Link: https://lkml.kernel.org/r/20230804165951.2661157-1-Liam.Howlett@oracle.com Link: https://lkml.kernel.org/r/20230804165951.2661157-2-Liam.Howlett@oracle.com Signed-off-by: Liam R. Howlett Cc: Matthew Wilcox (Oracle) Cc: Paul E. McKenney Cc: Suren Baghdasaryan Signed-off-by: Andrew Morton --- lib/maple_tree.c | 24 ++++++++++++++++++++---- 1 file changed, 20 insertions(+), 4 deletions(-) diff --git a/lib/maple_tree.c b/lib/maple_tree.c index a3d602cfd030..880ce0fcdcac 100644 --- a/lib/maple_tree.c +++ b/lib/maple_tree.c @@ -6833,11 +6833,27 @@ static void mt_dump_arange64(const struct maple_tree *mt, void *entry, int i; pr_cont(" contents: "); - for (i = 0; i < MAPLE_ARANGE64_SLOTS; i++) - pr_cont("%lu ", node->gap[i]); + for (i = 0; i < MAPLE_ARANGE64_SLOTS; i++) { + switch (format) { + case mt_dump_hex: + pr_cont("%lx ", node->gap[i]); + break; + default: + case mt_dump_dec: + pr_cont("%lu ", node->gap[i]); + } + } pr_cont("| %02X %02X| ", node->meta.end, node->meta.gap); - for (i = 0; i < MAPLE_ARANGE64_SLOTS - 1; i++) - pr_cont("%p %lu ", node->slot[i], node->pivot[i]); + for (i = 0; i < MAPLE_ARANGE64_SLOTS - 1; i++) { + switch (format) { + case mt_dump_hex: + pr_cont("%p %lX ", node->slot[i], node->pivot[i]); + break; + default: + case mt_dump_dec: + pr_cont("%p %lu ", node->slot[i], node->pivot[i]); + } + } pr_cont("%p\n", node->slot[i]); for (i = 0; i < MAPLE_ARANGE64_SLOTS; i++) { unsigned long last = max;