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

To: Dave Chinner <david@xxxxxxxxxxxxx>
Subject: Re: [PATCH 1/2] dax: pass bdev argument to dax_clear_blocks()
From: Ross Zwisler <ross.zwisler@xxxxxxxxxxxxxxx>
Date: Sun, 7 Feb 2016 18:44:09 -0700
Cc: Ross Zwisler <ross.zwisler@xxxxxxxxxxxxxxx>, linux-kernel@xxxxxxxxxxxxxxx, Theodore Ts'o <tytso@xxxxxxx>, Alexander Viro <viro@xxxxxxxxxxxxxxxxxx>, Andreas Dilger <adilger.kernel@xxxxxxxxx>, Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>, Dan Williams <dan.j.williams@xxxxxxxxx>, Jan Kara <jack@xxxxxxxx>, Matthew Wilcox <willy@xxxxxxxxxxxxxxx>, linux-ext4@xxxxxxxxxxxxxxx, linux-fsdevel@xxxxxxxxxxxxxxx, linux-mm@xxxxxxxxx, linux-nvdimm@xxxxxxxxxxxx, xfs@xxxxxxxxxxx
Delivered-to: xfs@xxxxxxxxxxx
In-reply-to: <20160207220329.GK31407@dastard>
Mail-followup-to: Ross Zwisler <ross.zwisler@xxxxxxxxxxxxxxx>, Dave Chinner <david@xxxxxxxxxxxxx>, linux-kernel@xxxxxxxxxxxxxxx, Theodore Ts'o <tytso@xxxxxxx>, Alexander Viro <viro@xxxxxxxxxxxxxxxxxx>, Andreas Dilger <adilger.kernel@xxxxxxxxx>, Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>, Dan Williams <dan.j.williams@xxxxxxxxx>, Jan Kara <jack@xxxxxxxx>, Matthew Wilcox <willy@xxxxxxxxxxxxxxx>, linux-ext4@xxxxxxxxxxxxxxx, linux-fsdevel@xxxxxxxxxxxxxxx, linux-mm@xxxxxxxxx, linux-nvdimm@xxxxxxxxxxxx, xfs@xxxxxxxxxxx
References: <1454829553-29499-1-git-send-email-ross.zwisler@xxxxxxxxxxxxxxx> <1454829553-29499-2-git-send-email-ross.zwisler@xxxxxxxxxxxxxxx> <20160207220329.GK31407@dastard>
User-agent: Mutt/1.5.24 (2015-08-30)
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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