linux-ext4 - Re: [PATCH 1/2] dax: pass bdev argument to dax_clear

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Date:	Sun, 7 Feb 2016 18:46:01 -0700
From:	Ross Zwisler <ross.zwisler@...ux.intel.com>
To:	Dan Williams <dan.j.williams@...el.com>
Cc:	Ross Zwisler <ross.zwisler@...ux.intel.com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Theodore Ts'o <tytso@....edu>,
	Alexander Viro <viro@...iv.linux.org.uk>,
	Andreas Dilger <adilger.kernel@...ger.ca>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Dave Chinner <david@...morbit.com>, Jan Kara <jack@...e.com>,
	Matthew Wilcox <willy@...ux.intel.com>,
	linux-ext4 <linux-ext4@...r.kernel.org>,
	linux-fsdevel <linux-fsdevel@...r.kernel.org>,
	Linux MM <linux-mm@...ck.org>,
	"linux-nvdimm@...ts.01.org" <linux-nvdimm@...ts.01.org>,
	XFS Developers <xfs@....sgi.com>
Subject: Re: [PATCH 1/2] dax: pass bdev argument to dax_clear_blocks()

On Sun, Feb 07, 2016 at 10:19:29AM -0800, Dan Williams wrote:
> On Sat, Feb 6, 2016 at 11:19 PM, Ross Zwisler
> <ross.zwisler@...ux.intel.com> 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.
> >
> > Signed-off-by: Ross Zwisler <ross.zwisler@...ux.intel.com>
> > ---
> >  fs/dax.c               | 4 ++--
> >  fs/ext2/inode.c        | 5 +++--
> >  fs/xfs/xfs_aops.c      | 2 +-
> >  fs/xfs/xfs_aops.h      | 1 +
> >  fs/xfs/xfs_bmap_util.c | 4 +++-
> >  include/linux/dax.h    | 3 ++-
> >  6 files changed, 12 insertions(+), 7 deletions(-)
> >
> > diff --git a/fs/dax.c b/fs/dax.c
> > index 227974a..4592241 100644
> > --- a/fs/dax.c
> > +++ b/fs/dax.c
> > @@ -83,9 +83,9 @@ struct page *read_dax_sector(struct block_device *bdev, sector_t n)
> >   * and hence this means the stack from this point must follow GFP_NOFS
> >   * semantics for all operations.
> >   */
> > -int dax_clear_blocks(struct inode *inode, sector_t block, long _size)
> > +int dax_clear_blocks(struct inode *inode, struct block_device *bdev,
> > +               sector_t block, long _size)
> 
> Since this is a bdev relative routine we should also resolve the
> sector, i.e. the signature should drop the inode:
> 
> int dax_clear_sectors(struct block_device *bdev, sector_t sector, long _size)

The inode is still needed because dax_clear_blocks() needs inode->i_blkbits.
Unless there is some easy way to get this from the bdev that I'm not seeing?
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