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Date:   Fri, 8 Dec 2023 18:22:49 +0100
From:   Jan Kara <jack@suse.cz>
To:     Alexander Mikhalitsyn <aleksandr.mikhalitsyn@canonical.com>
Cc:     brauner@kernel.org, linux-fsdevel@vger.kernel.org,
        Jan Kara <jack@suse.cz>,
        Alexander Viro <viro@zeniv.linux.org.uk>,
        linux-kernel@vger.kernel.org
Subject: Re: [PATCH] fs: super: use GFP_KERNEL instead of GFP_USER for super
 block allocation
Message-ID: <20231208172249.3274eh4cjdnwhjch@quack3>
References: <20231208151022.156273-1-aleksandr.mikhalitsyn@canonical.com>
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In-Reply-To: <20231208151022.156273-1-aleksandr.mikhalitsyn@canonical.com>
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On Fri 08-12-23 16:10:22, Alexander Mikhalitsyn wrote:
> There is no reason to use a GFP_USER flag for struct super_block allocation
> in the alloc_super(). Instead, let's use GFP_KERNEL for that.
> 
> From the memory management perspective, the only difference between
> GFP_USER and GFP_KERNEL is that GFP_USER allocations are tied to a cpuset,
> while GFP_KERNEL ones are not.
> 
> There is no real issue and this is not a candidate to go to the stable,
> but let's fix it for a consistency sake.
> 
> Cc: Jan Kara <jack@suse.cz>
> Cc: Alexander Viro <viro@zeniv.linux.org.uk>
> Cc: Christian Brauner <brauner@kernel.org>
> Cc: linux-fsdevel@vger.kernel.org
> Cc: linux-kernel@vger.kernel.org
> Signed-off-by: Alexander Mikhalitsyn <aleksandr.mikhalitsyn@canonical.com>

Yeah, since we allocate other filesystem objects with GFP_KERNEL as well I
agree. Feel free to add:

Reviewed-by: Jan Kara <jack@suse.cz>

								Honza

> diff --git a/fs/super.c b/fs/super.c
> index 076392396e72..6fe482371633 100644
> --- a/fs/super.c
> +++ b/fs/super.c
> @@ -323,7 +323,7 @@ static void destroy_unused_super(struct super_block *s)
>  static struct super_block *alloc_super(struct file_system_type *type, int flags,
>  				       struct user_namespace *user_ns)
>  {
> -	struct super_block *s = kzalloc(sizeof(struct super_block),  GFP_USER);
> +	struct super_block *s = kzalloc(sizeof(struct super_block), GFP_KERNEL);
>  	static const struct super_operations default_op;
>  	int i;
>  
> -- 
> 2.34.1
> 
-- 
Jan Kara <jack@suse.com>
SUSE Labs, CR