diff options
author | Nicholas Piggin <npiggin@gmail.com> | 2022-04-22 09:01:05 +0300 |
---|---|---|
committer | Linus Torvalds <torvalds@linux-foundation.org> | 2022-04-22 19:20:16 +0300 |
commit | 3b8000ae185cb068adbda5f966a3835053c85fd4 (patch) | |
tree | 7b70caa81822cde71f0fb347822aa13772461f9f /mm/vmalloc.c | |
parent | d569e86915b7f2f9795588591c8d5ea0b66481cb (diff) | |
download | linux-3b8000ae185cb068adbda5f966a3835053c85fd4.tar.xz |
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>
Diffstat (limited to 'mm/vmalloc.c')
-rw-r--r-- | mm/vmalloc.c | 36 |
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); } /* |