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Date:   Tue, 27 Jun 2023 23:11:53 -0700
From:   Christoph Hellwig <hch@infradead.org>
To:     "zhaoyang.huang" <zhaoyang.huang@unisoc.com>
Cc:     Alexander Viro <viro@zeniv.linux.org.uk>,
        Andrew Morton <akpm@linux-foundation.org>,
        Matthew Wilcox <willy@infradead.org>,
        Vlastimil Babka <vbabka@suse.cz>,
        Yang Shi <shy828301@gmail.com>,
        Suren Baghdasaryan <surenb@google.com>,
        Yu Zhao <yuzhao@google.com>, linux-mm@kvack.org,
        linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org,
        Zhaoyang Huang <huangzhaoyang@gmail.com>, ke.wang@unisoc.com,
        Christian Brauner <christian@brauner.io>
Subject: Re: [PATCH] mm: introduce statistic for inode's gen&tier
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On Tue, Jun 27, 2023 at 05:17:18PM +0800, zhaoyang.huang wrote:
> --- a/include/linux/fs.h
> +++ b/include/linux/fs.h
> @@ -434,6 +434,8 @@ struct address_space {
>  	struct rb_root_cached	i_mmap;
>  	struct rw_semaphore	i_mmap_rwsem;
>  	unsigned long		nrpages;
> +	atomic_long_t		gen;
> +	atomic_long_t		tier;

This increases the size of the inode by 16 byes, and better have really
good data supporting it, as increases of the inode size impact a lot
of workloads.