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authorNicholas Piggin <npiggin@gmail.com>2022-04-22 16:01:05 +1000
committerLinus Torvalds <torvalds@linux-foundation.org>2022-04-22 09:20:16 -0700
commit3b8000ae185cb068adbda5f966a3835053c85fd4 (patch)
tree7b70caa81822cde71f0fb347822aa13772461f9f
parentd569e86915b7f2f9795588591c8d5ea0b66481cb (diff)
mm/vmalloc: huge vmalloc backing pages should be split rather than compound
Huge vmalloc higher-order backing pages were allocated with __GFP_COMP in order to allow the sub-pages to be refcounted by callers such as "remap_vmalloc_page [sic]" (remap_vmalloc_range). However a similar problem exists for other struct page fields callers use, for example fb_deferred_io_fault() takes a vmalloc'ed page and not only refcounts it but uses ->lru, ->mapping, ->index. This is not compatible with compound sub-pages, and can cause bad page state issues like BUG: Bad page state in process swapper/0 pfn:00743 page:(____ptrval____) refcount:0 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x743 flags: 0x7ffff000000000(node=0|zone=0|lastcpupid=0x7ffff) raw: 007ffff000000000 c00c00000001d0c8 c00c00000001d0c8 0000000000000000 raw: 0000000000000000 0000000000000000 00000000ffffffff 0000000000000000 page dumped because: corrupted mapping in tail page Modules linked in: CPU: 0 PID: 1 Comm: swapper/0 Not tainted 5.18.0-rc3-00082-gfc6fff4a7ce1-dirty #2810 Call Trace: dump_stack_lvl+0x74/0xa8 (unreliable) bad_page+0x12c/0x170 free_tail_pages_check+0xe8/0x190 free_pcp_prepare+0x31c/0x4e0 free_unref_page+0x40/0x1b0 __vunmap+0x1d8/0x420 ... The correct approach is to use split high-order pages for the huge vmalloc backing. These allow callers to treat them in exactly the same way as individually-allocated order-0 pages. Link: https://lore.kernel.org/all/14444103-d51b-0fb3-ee63-c3f182f0b546@molgen.mpg.de/ Signed-off-by: Nicholas Piggin <npiggin@gmail.com> Cc: Paul Menzel <pmenzel@molgen.mpg.de> Cc: Song Liu <songliubraving@fb.com> Cc: Rick Edgecombe <rick.p.edgecombe@intel.com> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
-rw-r--r--mm/vmalloc.c36
1 files changed, 21 insertions, 15 deletions
diff --git a/mm/vmalloc.c b/mm/vmalloc.c
index 07da85ae825b..cadfbb5155ea 100644
--- a/mm/vmalloc.c
+++ b/mm/vmalloc.c
@@ -2653,15 +2653,18 @@ static void __vunmap(const void *addr, int deallocate_pages)
vm_remove_mappings(area, deallocate_pages);
if (deallocate_pages) {
- unsigned int page_order = vm_area_page_order(area);
- int i, step = 1U << page_order;
+ int i;
- for (i = 0; i < area->nr_pages; i += step) {
+ for (i = 0; i < area->nr_pages; i++) {
struct page *page = area->pages[i];
BUG_ON(!page);
- mod_memcg_page_state(page, MEMCG_VMALLOC, -step);
- __free_pages(page, page_order);
+ mod_memcg_page_state(page, MEMCG_VMALLOC, -1);
+ /*
+ * High-order allocs for huge vmallocs are split, so
+ * can be freed as an array of order-0 allocations
+ */
+ __free_pages(page, 0);
cond_resched();
}
atomic_long_sub(area->nr_pages, &nr_vmalloc_pages);
@@ -2914,12 +2917,7 @@ vm_area_alloc_pages(gfp_t gfp, int nid,
if (nr != nr_pages_request)
break;
}
- } else
- /*
- * Compound pages required for remap_vmalloc_page if
- * high-order pages.
- */
- gfp |= __GFP_COMP;
+ }
/* High-order pages or fallback path if "bulk" fails. */
@@ -2933,6 +2931,15 @@ vm_area_alloc_pages(gfp_t gfp, int nid,
page = alloc_pages_node(nid, gfp, order);
if (unlikely(!page))
break;
+ /*
+ * Higher order allocations must be able to be treated as
+ * indepdenent small pages by callers (as they can with
+ * small-page vmallocs). Some drivers do their own refcounting
+ * on vmalloc_to_page() pages, some use page->mapping,
+ * page->lru, etc.
+ */
+ if (order)
+ split_page(page, order);
/*
* Careful, we allocate and map page-order pages, but
@@ -2992,11 +2999,10 @@ static void *__vmalloc_area_node(struct vm_struct *area, gfp_t gfp_mask,
atomic_long_add(area->nr_pages, &nr_vmalloc_pages);
if (gfp_mask & __GFP_ACCOUNT) {
- int i, step = 1U << page_order;
+ int i;
- for (i = 0; i < area->nr_pages; i += step)
- mod_memcg_page_state(area->pages[i], MEMCG_VMALLOC,
- step);
+ for (i = 0; i < area->nr_pages; i++)
+ mod_memcg_page_state(area->pages[i], MEMCG_VMALLOC, 1);
}
/*