[patch 094/262] mm/vmalloc: check various alignments when debugging

Andrew Morton
2021-11-05T20:39:37Z

From: "Uladzislau Rezki (Sony)" <urezki@gmail.com>
Subject: mm/vmalloc: check various alignments when debugging

Before we did not guarantee a free block with lowest start address for
allocations with alignment >= PAGE_SIZE. Because an alignment overhead
was included into a search length like below:

length = size + align - 1;

doing so we make sure that a bigger block would fit after applying an
alignment adjustment. Now there is no such limitation, i.e. any
alignment that user wants to apply will result to a lowest address of
returned free area.

Link: https://lkml.kernel.org/r/20211004142829.22222-2-urezki@gmail.com
Signed-off-by: Uladzislau Rezki (Sony) <urezki@gmail.com>
Cc: Christoph Hellwig <hch@infradead.org>
Cc: David Hildenbrand <david@redhat.com>
Cc: Hillf Danton <hdanton@sina.com>
Cc: Matthew Wilcox <willy@infradead.org>
Cc: Mel Gorman <mgorman@suse.de>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Nicholas Piggin <npiggin@gmail.com>
Cc: Oleksiy Avramchenko <oleksiy.avramchenko@sonymobile.com>
Cc: Ping Fang <pifang@redhat.com>
Cc: Steven Rostedt <rostedt@goodmis.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---

mm/vmalloc.c | 8 ++++----
1 file changed, 4 insertions(+), 4 deletions(-)

--- a/mm/vmalloc.c~mm-vmalloc-check-various-alignments-when-debugging
+++ a/mm/vmalloc.c
@@ -1269,7 +1269,7 @@ find_vmap_lowest_linear_match(unsigned l
}

static void
-find_vmap_lowest_match_check(unsigned long size)
+find_vmap_lowest_match_check(unsigned long size, unsigned long align)
{
struct vmap_area *va_1, *va_2;
unsigned long vstart;
@@ -1278,8 +1278,8 @@ find_vmap_lowest_match_check(unsigned lo
get_random_bytes(&rnd, sizeof(rnd));
vstart = VMALLOC_START + rnd;

- va_1 = find_vmap_lowest_match(size, 1, vstart);
- va_2 = find_vmap_lowest_linear_match(size, 1, vstart);
+ va_1 = find_vmap_lowest_match(size, align, vstart);
+ va_2 = find_vmap_lowest_linear_match(size, align, vstart);

if (va_1 != va_2)
pr_emerg("not lowest: t: 0x%p, l: 0x%p, v: 0x%lx\n",
@@ -1458,7 +1458,7 @@ __alloc_vmap_area(unsigned long size, un
return vend;

#if DEBUG_AUGMENT_LOWEST_MATCH_CHECK
- find_vmap_lowest_match_check(size);
+ find_vmap_lowest_match_check(size, align);
#endif

return nva_start_addr;
_