linux-ext4 - Re: [PATCH 2/2] iomap: bmap: Remove the WARN and return the proper block address

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Date:   Fri, 24 Apr 2020 10:48:15 -0700
From:   "Darrick J. Wong" <darrick.wong@...cle.com>
To:     Ritesh Harjani <riteshh@...ux.ibm.com>
Cc:     linux-fsdevel@...r.kernel.org, linux-xfs@...r.kernel.org,
        Alexander Viro <viro@...iv.linux.org.uk>,
        Christoph Hellwig <hch@...radead.org>,
        Jan Kara <jack@...e.com>, tytso@....edu,
        "Aneesh Kumar K . V" <aneesh.kumar@...ux.ibm.com>,
        linux-ext4@...r.kernel.org
Subject: Re: [PATCH 2/2] iomap: bmap: Remove the WARN and return the proper
 block address

On Fri, Apr 24, 2020 at 12:52:18PM +0530, Ritesh Harjani wrote:
> iomap_bmap() could be called from either of these two paths.
> Either when a user is calling an ioctl_fibmap() interface to get
> the block mapping address or by some filesystem via use of bmap()
> internal kernel API.
> bmap() kernel API is well equipped with handling of u64 addresses.
> 
> WARN condition in iomap_bmap_actor() was mainly added to warn all
> the fibmap users. But now that in previous patch we have directly added
> this WARN condition for all fibmap users and also made sure to return 0
> as block map address in case if addr > INT_MAX. 
> So we can now remove this logic from here.
> 
> Signed-off-by: Ritesh Harjani <riteshh@...ux.ibm.com>
> ---
>  fs/iomap/fiemap.c | 5 +----
>  1 file changed, 1 insertion(+), 4 deletions(-)
> 
> diff --git a/fs/iomap/fiemap.c b/fs/iomap/fiemap.c
> index bccf305ea9ce..d55e8f491a5e 100644
> --- a/fs/iomap/fiemap.c
> +++ b/fs/iomap/fiemap.c
> @@ -117,10 +117,7 @@ iomap_bmap_actor(struct inode *inode, loff_t pos, loff_t length,
>  
>  	if (iomap->type == IOMAP_MAPPED) {
>  		addr = (pos - iomap->offset + iomap->addr) >> inode->i_blkbits;
> -		if (addr > INT_MAX)
> -			WARN(1, "would truncate bmap result\n");

Frankly I would've combined these two patches to make it more obvious
that we're hoisting a FIBMAP constraint check from iomap into the ioctl
handler.

--D

> -		else
> -			*bno = addr;
> +		*bno = addr;
>  	}
>  	return 0;
>  }
> -- 
> 2.21.0
>