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Date: Thu, 5 Jun 2025 12:57:24 -0700
From: Andrew Morton <akpm@linux-foundation.org>
To: Kemeng Shi <shikemeng@huaweicloud.com>
Cc: hughd@google.com, baolin.wang@linux.alibaba.com, willy@infradead.org,
 linux-mm@kvack.org, linux-kernel@vger.kernel.org,
 linux-fsdevel@vger.kernel.org
Subject: Re: [PATCH 1/7] mm: shmem: correctly pass alloced parameter to
 shmem_recalc_inode() to avoid WARN_ON()
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On Fri,  6 Jun 2025 06:10:31 +0800 Kemeng Shi <shikemeng@huaweicloud.com> wrote:

> As noted in the comments, we need to release block usage for swap entry
> which was replaced with poisoned swap entry. However, no block usage is
> actually freed by calling shmem_recalc_inode(inode, -nr_pages, -nr_pages).
> Instead, call shmem_recalc_inode(inode, 0, -nr_pages) can correctly release
> the block usage.
> 
> ...
>
> --- a/mm/shmem.c
> +++ b/mm/shmem.c
> @@ -2145,7 +2145,7 @@ static void shmem_set_folio_swapin_error(struct inode *inode, pgoff_t index,
>  	 * won't be 0 when inode is released and thus trigger WARN_ON(i_blocks)
>  	 * in shmem_evict_inode().
>  	 */
> -	shmem_recalc_inode(inode, -nr_pages, -nr_pages);
> +	shmem_recalc_inode(inode, 0, -nr_pages);
>  	swap_free_nr(swap, nr_pages);
>  }

Huh, three years ago.  What do we think might be the userspace-visible
runtime effects of this?