From 9f531973dff39c671219352573ad5df6d0d9a58c Mon Sep 17 00:00:00 2001 From: "Uladzislau Rezki (Sony)" Date: Fri, 5 Nov 2021 13:39:31 -0700 Subject: [PATCH] mm/vmalloc: do not adjust the search size for alignment overhead We used to include an alignment overhead into a search length, in that case we guarantee that a found area will definitely fit after applying a specific alignment that user specifies. From the other hand we do not guarantee that an area has the lowest address if an alignment is >= PAGE_SIZE. It means that, when a user specifies a special alignment together with a range that corresponds to an exact requested size then an allocation will fail. This is what happens to KASAN, it wants the free block that exactly matches a specified range during onlining memory banks: [root@vm-0 fedora]# echo online > /sys/devices/system/memory/memory82/state [root@vm-0 fedora]# echo online > /sys/devices/system/memory/memory83/state [root@vm-0 fedora]# echo online > /sys/devices/system/memory/memory85/state [root@vm-0 fedora]# echo online > /sys/devices/system/memory/memory84/state vmap allocation for size 16777216 failed: use vmalloc= to increase size bash: vmalloc: allocation failure: 16777216 bytes, mode:0x6000c0(GFP_KERNEL), nodemask=(null),cpuset=/,mems_allowed=0 CPU: 4 PID: 1644 Comm: bash Kdump: loaded Not tainted 4.18.0-339.el8.x86_64+debug #1 Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS rel-1.14.0-0-g155821a1990b-prebuilt.qemu.org 04/01/2014 Call Trace: dump_stack+0x8e/0xd0 warn_alloc.cold.90+0x8a/0x1b2 ? zone_watermark_ok_safe+0x300/0x300 ? slab_free_freelist_hook+0x85/0x1a0 ? __get_vm_area_node+0x240/0x2c0 ? kfree+0xdd/0x570 ? kmem_cache_alloc_node_trace+0x157/0x230 ? notifier_call_chain+0x90/0x160 __vmalloc_node_range+0x465/0x840 ? mark_held_locks+0xb7/0x120 Fix it by making sure that find_vmap_lowest_match() returns lowest start address with any given alignment value, i.e. for alignments bigger then PAGE_SIZE the algorithm rolls back toward parent nodes checking right sub-trees if the most left free block did not fit due to alignment overhead. Link: https://lkml.kernel.org/r/20211004142829.22222-1-urezki@gmail.com Fixes: 68ad4a330433 ("mm/vmalloc.c: keep track of free blocks for vmap allocation") Signed-off-by: Uladzislau Rezki (Sony) Reported-by: Ping Fang Tested-by: David Hildenbrand Reviewed-by: David Hildenbrand Cc: Mel Gorman Cc: Christoph Hellwig Cc: Matthew Wilcox Cc: Nicholas Piggin Cc: Hillf Danton Cc: Michal Hocko Cc: Oleksiy Avramchenko Cc: Steven Rostedt Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- mm/vmalloc.c | 22 +++++++++++++--------- 1 file changed, 13 insertions(+), 9 deletions(-) diff --git a/mm/vmalloc.c b/mm/vmalloc.c index 0a740fb055ec..0d835bd7fb5f 100644 --- a/mm/vmalloc.c +++ b/mm/vmalloc.c @@ -1195,18 +1195,14 @@ find_vmap_lowest_match(unsigned long size, { struct vmap_area *va; struct rb_node *node; - unsigned long length; /* Start from the root. */ node = free_vmap_area_root.rb_node; - /* Adjust the search size for alignment overhead. */ - length = size + align - 1; - while (node) { va = rb_entry(node, struct vmap_area, rb_node); - if (get_subtree_max_size(node->rb_left) >= length && + if (get_subtree_max_size(node->rb_left) >= size && vstart < va->va_start) { node = node->rb_left; } else { @@ -1216,9 +1212,9 @@ find_vmap_lowest_match(unsigned long size, /* * Does not make sense to go deeper towards the right * sub-tree if it does not have a free block that is - * equal or bigger to the requested search length. + * equal or bigger to the requested search size. */ - if (get_subtree_max_size(node->rb_right) >= length) { + if (get_subtree_max_size(node->rb_right) >= size) { node = node->rb_right; continue; } @@ -1226,15 +1222,23 @@ find_vmap_lowest_match(unsigned long size, /* * OK. We roll back and find the first right sub-tree, * that will satisfy the search criteria. It can happen - * only once due to "vstart" restriction. + * due to "vstart" restriction or an alignment overhead + * that is bigger then PAGE_SIZE. */ while ((node = rb_parent(node))) { va = rb_entry(node, struct vmap_area, rb_node); if (is_within_this_va(va, size, align, vstart)) return va; - if (get_subtree_max_size(node->rb_right) >= length && + if (get_subtree_max_size(node->rb_right) >= size && vstart <= va->va_start) { + /* + * Shift the vstart forward. Please note, we update it with + * parent's start address adding "1" because we do not want + * to enter same sub-tree after it has already been checked + * and no suitable free block found there. + */ + vstart = va->va_start + 1; node = node->rb_right; break; } -- 2.11.0