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mm/vmalloc: do not adjust the search size for alignment overhead

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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=<size> 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: 68ad4a3304 ("mm/vmalloc.c: keep track of free blocks for vmap allocation")
Signed-off-by: Uladzislau Rezki (Sony) <urezki@gmail.com>
Reported-by: Ping Fang <pifang@redhat.com>
Tested-by: David Hildenbrand <david@redhat.com>
Reviewed-by: David Hildenbrand <david@redhat.com>
Cc: Mel Gorman <mgorman@suse.de>
Cc: Christoph Hellwig <hch@infradead.org>
Cc: Matthew Wilcox <willy@infradead.org>
Cc: Nicholas Piggin <npiggin@gmail.com>
Cc: Hillf Danton <hdanton@sina.com>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Oleksiy Avramchenko <oleksiy.avramchenko@sonymobile.com>
Cc: Steven Rostedt <rostedt@goodmis.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Uladzislau Rezki (Sony) 2021-11-05 13:39:31 -07:00 committed by Linus Torvalds
parent 7cc7913e8e
commit 9f531973df
1 changed files with 13 additions and 9 deletions
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22
mm/vmalloc.c
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@ -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;
}