Re: [PATCH 1/2] dax: pass bdev argument to dax_clear_blocks()

From: Ross Zwisler <ross.zwisler@linux.intel.com>
To: Dave Chinner <david@fromorbit.com>
Cc: Ross Zwisler <ross.zwisler@linux.intel.com>,
	linux-kernel@vger.kernel.org, Theodore Ts'o <tytso@mit.edu>,
	Alexander Viro <viro@zeniv.linux.org.uk>,
	Andreas Dilger <adilger.kernel@dilger.ca>,
	Andrew Morton <akpm@linux-foundation.org>,
	Dan Williams <dan.j.williams@intel.com>, Jan Kara <jack@suse.com>,
	Matthew Wilcox <willy@linux.intel.com>,
	linux-ext4@vger.kernel.org, linux-fsdevel@vger.kernel.org,
	linux-mm@kvack.org, linux-nvdimm@lists.01.org, xfs@oss.sgi.com
Subject: Re: [PATCH 1/2] dax: pass bdev argument to dax_clear_blocks()
Date: Sun, 7 Feb 2016 18:44:09 -0700	[thread overview]
Message-ID: <20160208014409.GA2343@linux.intel.com> (raw)
In-Reply-To: <20160207220329.GK31407@dastard>

On Mon, Feb 08, 2016 at 09:03:29AM +1100, Dave Chinner wrote:
> On Sun, Feb 07, 2016 at 12:19:12AM -0700, Ross Zwisler wrote:
> > dax_clear_blocks() needs a valid struct block_device and previously it was
> > using inode->i_sb->s_bdev in all cases.  This is correct for normal inodes
> > on mounted ext2, ext4 and XFS filesystems, but is incorrect for DAX raw
> > block devices and for XFS real-time devices.
> > 
> > Instead, have the caller pass in a struct block_device pointer which it
> > knows to be correct.
> ....
> > diff --git a/fs/xfs/xfs_bmap_util.c b/fs/xfs/xfs_bmap_util.c
> > index 07ef29b..f722ba2 100644
> > --- a/fs/xfs/xfs_bmap_util.c
> > +++ b/fs/xfs/xfs_bmap_util.c
> > @@ -73,9 +73,11 @@ xfs_zero_extent(
> >  	xfs_daddr_t	sector = xfs_fsb_to_db(ip, start_fsb);
> >  	sector_t	block = XFS_BB_TO_FSBT(mp, sector);
> >  	ssize_t		size = XFS_FSB_TO_B(mp, count_fsb);
> > +	struct inode	*inode = VFS_I(ip);
> >  
> >  	if (IS_DAX(VFS_I(ip)))
> > -		return dax_clear_blocks(VFS_I(ip), block, size);
> > +		return dax_clear_blocks(inode, xfs_find_bdev_for_inode(inode),
> > +				block, size);
> 
> Get rid of the local inode variable and use VFS_I(ip) like the code
> originally did. Do not change code that is unrelated to the
> modifcation being made, especially when it results in making
> the code an inconsistent mess of mixed pointer constructs....

The local 'inode' variable was added to avoid multiple calls for VFS_I() for
the same 'ip'.  That said, I'm happy to make the change.

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