linux-kernel - Re: [linux-next:master] [mm] 0fa2857d23: WARNING:at_mm/page_alloc.c:#__alloc_pages

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Date: Mon, 24 Jun 2024 16:06:02 +0300
From: Usama Arif <usamaarif642@...il.com>
To: Yosry Ahmed <yosryahmed@...gle.com>,
 kernel test robot <oliver.sang@...el.com>
Cc: oe-lkp@...ts.linux.dev, lkp@...el.com,
 Linux Memory Management List <linux-mm@...ck.org>,
 Andrew Morton <akpm@...ux-foundation.org>,
 Chengming Zhou <chengming.zhou@...ux.dev>, Nhat Pham <nphamcs@...il.com>,
 David Hildenbrand <david@...hat.com>, "Huang, Ying" <ying.huang@...el.com>,
 Hugh Dickins <hughd@...gle.com>, Johannes Weiner <hannes@...xchg.org>,
 Matthew Wilcox <willy@...radead.org>, Shakeel Butt <shakeel.butt@...ux.dev>,
 Andi Kleen <ak@...ux.intel.com>, linux-kernel@...r.kernel.org
Subject: Re: [linux-next:master] [mm] 0fa2857d23:
 WARNING:at_mm/page_alloc.c:#__alloc_pages_noprof


On 24/06/2024 15:05, Yosry Ahmed wrote:
> On Mon, Jun 24, 2024 at 1:49 AM kernel test robot <oliver.sang@...el.com> wrote:
>>
>>
>> Hello,
>>
>> kernel test robot noticed "WARNING:at_mm/page_alloc.c:#__alloc_pages_noprof" on:
>>
>> commit: 0fa2857d23aa170e5e28d13c467b303b0065aad8 ("mm: store zero pages to be swapped out in a bitmap")
>> https://git.kernel.org/cgit/linux/kernel/git/next/linux-next.git master
> This is coming from WARN_ON_ONCE_GFP(order > MAX_PAGE_ORDER, gfp), and
> is triggered by the new bitmap_zalloc() call in the swapon path. For a
> sufficiently large swapfile, bitmap_zalloc() (which uses kmalloc()
> under the hood) cannot be used to allocate the bitmap.
>
> Usama, I think we want to use a variant of kvmalloc() here.

Yes, just testing with below diff now. The patch is not in mm-stable 
yet, so will just send another revision with below diff included. Thanks!


diff --git a/mm/swapfile.c b/mm/swapfile.c
index 0b8270359bcf..2263f71baa31 100644
--- a/mm/swapfile.c
+++ b/mm/swapfile.c
@@ -2643,7 +2643,7 @@ SYSCALL_DEFINE1(swapoff, const char __user *, 
specialfile)
         free_percpu(p->cluster_next_cpu);
         p->cluster_next_cpu = NULL;
         vfree(swap_map);
-       bitmap_free(p->zeromap);
+       kvfree(p->zeromap);
         kvfree(cluster_info);
         /* Destroy swap account information */
         swap_cgroup_swapoff(p->type);
@@ -3170,7 +3170,7 @@ SYSCALL_DEFINE2(swapon, const char __user *, 
specialfile, int, swap_flags)
                 goto bad_swap_unlock_inode;
         }

-       p->zeromap = bitmap_zalloc(maxpages, GFP_KERNEL);
+       p->zeromap = kvzalloc(DIV_ROUND_UP(maxpages, 8), GFP_KERNEL);
         if (!p->zeromap) {
                 error = -ENOMEM;
                 goto bad_swap_unlock_inode;