+ vmalloc-fix-accounting-with-i915.patch added to mm-hotfixes-unstable branch

+ vmalloc-fix-accounting-with-i915.patch added to mm-hotfixes-unstable branch

[Andrew Morton]

The patch titled
     Subject: vmalloc: fix accounting with i915
has been added to the -mm mm-hotfixes-unstable branch.  Its filename is
     vmalloc-fix-accounting-with-i915.patch

This patch will shortly appear at
     https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/vmalloc-fix-accounting-with-i915.patch

This patch will later appear in the mm-hotfixes-unstable branch at
    git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm

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------------------------------------------------------
From: "Matthew Wilcox (Oracle)" <willy@infradead.org>
Subject: vmalloc: fix accounting with i915
Date: Wed, 11 Dec 2024 20:25:37 +0000

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>
Cc: Christoph Hellwig <hch@lst.de>
Cc: Michal Hocko <mhocko@kernel.org>
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>
---

 mm/vmalloc.c |    6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

--- a/mm/vmalloc.c~vmalloc-fix-accounting-with-i915
+++ a/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);
 }
_

Patches currently in -mm which might be from willy@infradead.org are

vmalloc-fix-accounting-with-i915.patch
mm-page_alloc-cache-page_zone-result-in-free_unref_page.patch
mm-make-alloc_pages_mpol-static.patch
mm-page_alloc-export-free_frozen_pages-instead-of-free_unref_page.patch
mm-page_alloc-move-set_page_refcounted-to-callers-of-post_alloc_hook.patch
mm-page_alloc-move-set_page_refcounted-to-callers-of-prep_new_page.patch
mm-page_alloc-move-set_page_refcounted-to-callers-of-get_page_from_freelist.patch
mm-page_alloc-move-set_page_refcounted-to-callers-of-__alloc_pages_cpuset_fallback.patch
mm-page_alloc-move-set_page_refcounted-to-callers-of-__alloc_pages_may_oom.patch
mm-page_alloc-move-set_page_refcounted-to-callers-of-__alloc_pages_direct_compact.patch
mm-page_alloc-move-set_page_refcounted-to-callers-of-__alloc_pages_direct_reclaim.patch
mm-page_alloc-move-set_page_refcounted-to-callers-of-__alloc_pages_slowpath.patch
mm-page_alloc-move-set_page_refcounted-to-end-of-__alloc_pages.patch
mm-page_alloc-add-__alloc_frozen_pages.patch
mm-mempolicy-add-alloc_frozen_pages.patch
slab-allocate-frozen-pages.patch