linux-kernel - Re: [PATCH] zonefs: Call page_address() on page acquired with GFP

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Message-ID: <YsSv656Uc873foaA@iweiny-desk3>
Date:   Tue, 5 Jul 2022 14:40:59 -0700
From:   Ira Weiny <ira.weiny@...el.com>
To:     "Fabio M. De Francesco" <fmdefrancesco@...il.com>
CC:     Damien Le Moal <damien.lemoal@...nsource.wdc.com>,
        Naohiro Aota <naohiro.aota@....com>,
        Johannes Thumshirn <jth@...nel.org>,
        <linux-fsdevel@...r.kernel.org>, <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] zonefs: Call page_address() on page acquired with
 GFP_KERNEL flag

On Tue, Jul 05, 2022 at 04:22:02PM +0200, Fabio M. De Francesco wrote:
> zonefs_read_super() acquires a page with alloc_page(GFP_KERNEL). That
> page cannot come from ZONE_HIGHMEM, thus there's no need to map it with
> kmap().
> 
> Therefore, use a plain page_address() on that page.
> 
> Suggested-by: Ira Weiny <ira.weiny@...el.com>

Reviewed-by: Ira Weiny <ira.weiny@...el.com>

> Signed-off-by: Fabio M. De Francesco <fmdefrancesco@...il.com>
> ---
>  fs/zonefs/super.c | 16 +++++++---------
>  1 file changed, 7 insertions(+), 9 deletions(-)
> 
> diff --git a/fs/zonefs/super.c b/fs/zonefs/super.c
> index 053299758deb..bd4e4be97a68 100644
> --- a/fs/zonefs/super.c
> +++ b/fs/zonefs/super.c
> @@ -1687,11 +1687,11 @@ static int zonefs_read_super(struct super_block *sb)
>  	if (ret)
>  		goto free_page;
>  
> -	super = kmap(page);
> +	super = page_address(page);
>  
>  	ret = -EINVAL;
>  	if (le32_to_cpu(super->s_magic) != ZONEFS_MAGIC)
> -		goto unmap;
> +		goto free_page;
>  
>  	stored_crc = le32_to_cpu(super->s_crc);
>  	super->s_crc = 0;
> @@ -1699,14 +1699,14 @@ static int zonefs_read_super(struct super_block *sb)
>  	if (crc != stored_crc) {
>  		zonefs_err(sb, "Invalid checksum (Expected 0x%08x, got 0x%08x)",
>  			   crc, stored_crc);
> -		goto unmap;
> +		goto free_page;
>  	}
>  
>  	sbi->s_features = le64_to_cpu(super->s_features);
>  	if (sbi->s_features & ~ZONEFS_F_DEFINED_FEATURES) {
>  		zonefs_err(sb, "Unknown features set 0x%llx\n",
>  			   sbi->s_features);
> -		goto unmap;
> +		goto free_page;
>  	}
>  
>  	if (sbi->s_features & ZONEFS_F_UID) {
> @@ -1714,7 +1714,7 @@ static int zonefs_read_super(struct super_block *sb)
>  				       le32_to_cpu(super->s_uid));
>  		if (!uid_valid(sbi->s_uid)) {
>  			zonefs_err(sb, "Invalid UID feature\n");
> -			goto unmap;
> +			goto free_page;
>  		}
>  	}
>  
> @@ -1723,7 +1723,7 @@ static int zonefs_read_super(struct super_block *sb)
>  				       le32_to_cpu(super->s_gid));
>  		if (!gid_valid(sbi->s_gid)) {
>  			zonefs_err(sb, "Invalid GID feature\n");
> -			goto unmap;
> +			goto free_page;
>  		}
>  	}
>  
> @@ -1732,14 +1732,12 @@ static int zonefs_read_super(struct super_block *sb)
>  
>  	if (memchr_inv(super->s_reserved, 0, sizeof(super->s_reserved))) {
>  		zonefs_err(sb, "Reserved area is being used\n");
> -		goto unmap;
> +		goto free_page;
>  	}
>  
>  	import_uuid(&sbi->s_uuid, super->s_uuid);
>  	ret = 0;
>  
> -unmap:
> -	kunmap(page);
>  free_page:
>  	__free_page(page);
>  
> -- 
> 2.36.1
>