vmalloc: fix accounting with i915

If the caller of vmap() specifies VM_MAP_PUT_PAGES (currently only the
i915 driver), we will decrement nr_vmalloc_pages and MEMCG_VMALLOC in
vfree().  These counters are incremented by vmalloc() but not by vmap() so
this will cause an underflow.  Check the VM_MAP_PUT_PAGES flag before
decrementing either counter.

Link: https://lkml.kernel.org/r/20241211202538.168311-1-willy@infradead.org
Fixes: b944afc9d64d ("mm: add a VM_MAP_PUT_PAGES flag for vmap")
Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
Acked-by: Johannes Weiner <hannes@cmpxchg.org>
Reviewed-by: Shakeel Butt <shakeel.butt@linux.dev>
Reviewed-by: Balbir Singh <balbirs@nvidia.com>
Acked-by: Michal Hocko <mhocko@suse.com>
Cc: Christoph Hellwig <hch@lst.de>
Cc: Muchun Song <muchun.song@linux.dev>
Cc: Roman Gushchin <roman.gushchin@linux.dev>
Cc: "Uladzislau Rezki (Sony)" <urezki@gmail.com>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

diff --git a/mm/vmalloc.c b/mm/vmalloc.c
index f009b21705c163a60a8d709ef44029c26d6761dd..5c88d0e90c209ab80ed9479c1ea726743fbb565f 100644 (file)
--- a/mm/vmalloc.c
+++ b/mm/vmalloc.c
@@ -3374,7 +3374,8 @@ void vfree(const void *addr)
                struct page *page = vm->pages[i];
 
                BUG_ON(!page);
-               mod_memcg_page_state(page, MEMCG_VMALLOC, -1);
+               if (!(vm->flags & VM_MAP_PUT_PAGES))
+                       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
@@ -3382,7 +3383,8 @@ void vfree(const void *addr)
                __free_page(page);
                cond_resched();
        }
-       atomic_long_sub(vm->nr_pages, &nr_vmalloc_pages);
+       if (!(vm->flags & VM_MAP_PUT_PAGES))
+               atomic_long_sub(vm->nr_pages, &nr_vmalloc_pages);
        kvfree(vm->pages);
        kfree(vm);
 }