RE: [PATCH v4 7/7] fs/xfs: Add dedupe support for fsdax

From: "ruansy.fnst@fujitsu.com" <ruansy.fnst@fujitsu.com>
To: Su Yue <l@damenly.su>
Cc: "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
	"linux-xfs@vger.kernel.org" <linux-xfs@vger.kernel.org>,
	"linux-nvdimm@lists.01.org" <linux-nvdimm@lists.01.org>,
	"linux-fsdevel@vger.kernel.org" <linux-fsdevel@vger.kernel.org>,
	"darrick.wong@oracle.com" <darrick.wong@oracle.com>,
	"willy@infradead.org" <willy@infradead.org>,
	"jack@suse.cz" <jack@suse.cz>,
	"viro@zeniv.linux.org.uk" <viro@zeniv.linux.org.uk>,
	"linux-btrfs@vger.kernel.org" <linux-btrfs@vger.kernel.org>,
	"david@fromorbit.com" <david@fromorbit.com>,
	"hch@lst.de" <hch@lst.de>, "rgoldwyn@suse.de" <rgoldwyn@suse.de>
Subject: RE: [PATCH v4 7/7] fs/xfs: Add dedupe support for fsdax
Date: Fri, 9 Apr 2021 01:56:48 +0000	[thread overview]
Message-ID: <OSAPR01MB291345BD169337AE2BCAA717F4739@OSAPR01MB2913.jpnprd01.prod.outlook.com> (raw)
In-Reply-To: <czv4syut.fsf@damenly.su>

> -----Original Message-----
> From: Su Yue <l@damenly.su>
> Subject: Re: [PATCH v4 7/7] fs/xfs: Add dedupe support for fsdax
> 
> 
> On Thu 08 Apr 2021 at 20:04, Shiyang Ruan <ruansy.fnst@fujitsu.com> wrote:
> 
> > Add xfs_break_two_dax_layouts() to break layout for tow dax files.
> > Then call compare range function only when files are both DAX or not.
> >
> > Signed-off-by: Shiyang Ruan <ruansy.fnst@fujitsu.com>
> >
> Not family with xfs code but reading code make my sleep better :) See bellow.
> 
> > ---
> >  fs/xfs/xfs_file.c    | 20 ++++++++++++++++++++
> >  fs/xfs/xfs_inode.c   |  8 +++++++-
> >  fs/xfs/xfs_inode.h   |  1 +
> >  fs/xfs/xfs_reflink.c |  5 +++--
> >  4 files changed, 31 insertions(+), 3 deletions(-)
> >
> > diff --git a/fs/xfs/xfs_file.c b/fs/xfs/xfs_file.c index
> > 5795d5d6f869..1fd457167c12 100644
> > --- a/fs/xfs/xfs_file.c
> > +++ b/fs/xfs/xfs_file.c
> > @@ -842,6 +842,26 @@ xfs_break_dax_layouts(
> >  			0, 0, xfs_wait_dax_page(inode));
> >  }
> >
> > +int
> > +xfs_break_two_dax_layouts(
> > +	struct inode		*src,
> > +	struct inode		*dest)
> > +{
> > +	int			error;
> > +	bool			retry = false;
> > +
> > +retry:
> >
> 'retry = false;' ? since xfs_break_dax_layouts() won't set retry to false if there is
> no busy page in inode->i_mapping.
> Dead loop will happen if retry is true once.

Yes, I should move 'retry=false;' under the retry label.

> 
> > +	error = xfs_break_dax_layouts(src, &retry);
> > +	if (error || retry)
> > +		goto retry;
> > +
> > +	error = xfs_break_dax_layouts(dest, &retry);
> > +	if (error || retry)
> > +		goto retry;
> > +
> > +	return error;
> > +}
> > +
> >  int
> >  xfs_break_layouts(
> >  	struct inode		*inode,
> > diff --git a/fs/xfs/xfs_inode.c b/fs/xfs/xfs_inode.c index
> > f93370bd7b1e..c01786917eef 100644
> > --- a/fs/xfs/xfs_inode.c
> > +++ b/fs/xfs/xfs_inode.c
> > @@ -3713,8 +3713,10 @@ xfs_ilock2_io_mmap(
> >  	struct xfs_inode	*ip2)
> >  {
> >  	int			ret;
> > +	struct inode		*inode1 = VFS_I(ip1);
> > +	struct inode		*inode2 = VFS_I(ip2);
> >
> > -	ret = xfs_iolock_two_inodes_and_break_layout(VFS_I(ip1),
> > VFS_I(ip2));
> > +	ret = xfs_iolock_two_inodes_and_break_layout(inode1, inode2);
> >  	if (ret)
> >  		return ret;
> >  	if (ip1 == ip2)
> > @@ -3722,6 +3724,10 @@ xfs_ilock2_io_mmap(
> >  	else
> >  		xfs_lock_two_inodes(ip1, XFS_MMAPLOCK_EXCL,
> >  				    ip2, XFS_MMAPLOCK_EXCL);
> > +
> > +	if (IS_DAX(inode1) && IS_DAX(inode2))
> > +		ret = xfs_break_two_dax_layouts(inode1, inode2);
> > +
> ret is ignored here.

Thanks, it's my mistake.

--
Thanks,
Ruan Shiyang.
> 
> --
> Su
> >  	return 0;
> >  }
> >
> > diff --git a/fs/xfs/xfs_inode.h b/fs/xfs/xfs_inode.h index
> > 88ee4c3930ae..5ef21924dddc 100644
> > --- a/fs/xfs/xfs_inode.h
> > +++ b/fs/xfs/xfs_inode.h
> > @@ -435,6 +435,7 @@ enum xfs_prealloc_flags {
> >
> >  int	xfs_update_prealloc_flags(struct xfs_inode *ip,
> >  				  enum xfs_prealloc_flags flags);
> > +int	xfs_break_two_dax_layouts(struct inode *inode1, struct
> > inode *inode2);
> >  int	xfs_break_layouts(struct inode *inode, uint *iolock,
> >  		enum layout_break_reason reason);
> >
> > diff --git a/fs/xfs/xfs_reflink.c b/fs/xfs/xfs_reflink.c index
> > a4cd6e8a7aa0..4426bcc8a985 100644
> > --- a/fs/xfs/xfs_reflink.c
> > +++ b/fs/xfs/xfs_reflink.c
> > @@ -29,6 +29,7 @@
> >  #include "xfs_iomap.h"
> >  #include "xfs_sb.h"
> >  #include "xfs_ag_resv.h"
> > +#include <linux/dax.h>
> >
> >  /*
> >   * Copy on Write of Shared Blocks
> > @@ -1324,8 +1325,8 @@ xfs_reflink_remap_prep(
> >  	if (XFS_IS_REALTIME_INODE(src) || XFS_IS_REALTIME_INODE(dest))
> >  		goto out_unlock;
> >
> > -	/* Don't share DAX file data for now. */
> > -	if (IS_DAX(inode_in) || IS_DAX(inode_out))
> > +	/* Don't share DAX file data with non-DAX file. */
> > +	if (IS_DAX(inode_in) != IS_DAX(inode_out))
> >  		goto out_unlock;
> >
> >  	if (!IS_DAX(inode_in))
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