Re: [PATCH 02/15] xfs: refactor clonerange preparation into a separate helper

["Darrick J. Wong" <darrick.wong@oracle.com>]

On Fri, Oct 05, 2018 at 03:28:09PM +1000, Dave Chinner wrote:
> On Thu, Oct 04, 2018 at 05:44:47PM -0700, Darrick J. Wong wrote:
> > From: Darrick J. Wong <darrick.wong@oracle.com>
> > 
> > Refactor all the reflink preparation steps into a separate helper that
> > we'll use to land all the upcoming fixes for insufficient input checks.
> 
> If I've read the patch right, this also changes the location of the
> page cache truncation, right?  i.e. it now happens in the
> xfs_reflink_remap_prep() function instead of after the remap?  I
> think the commit message needs to mention that because it's a fix to
> incorrect behaviour....

Right.  Sorry I forgot to put that in the changelog.

> I've added:
> 
> --
> This rework also moves the invalidation of the destination range to
> the prep function so that it is done before the range is remapped.
> This ensures that nobody can access the data in range being remapped
> until the remap is complete.
> --
> 
> Sound OK?

Yep.

--D


> Otherwise this looks fine.
> 
> Reviewed-by: Dave Chinner <dchinner@redhat.com>
> 
> -Dave.
> 
> > 
> > Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
> > ---
> >  fs/xfs/xfs_reflink.c |   96 +++++++++++++++++++++++++++++++++++++-------------
> >  1 file changed, 71 insertions(+), 25 deletions(-)
> > 
> > 
> > diff --git a/fs/xfs/xfs_reflink.c b/fs/xfs/xfs_reflink.c
> > index 38f405415b88..80ca9b6793cd 100644
> > --- a/fs/xfs/xfs_reflink.c
> > +++ b/fs/xfs/xfs_reflink.c
> > @@ -1195,11 +1195,33 @@ xfs_iolock_two_inodes_and_break_layout(
> >  	return 0;
> >  }
> >  
> > +/* Unlock both inodes after they've been prepped for a range clone. */
> > +STATIC void
> > +xfs_reflink_remap_unlock(
> > +	struct file		*file_in,
> > +	struct file		*file_out)
> > +{
> > +	struct inode		*inode_in = file_inode(file_in);
> > +	struct xfs_inode	*src = XFS_I(inode_in);
> > +	struct inode		*inode_out = file_inode(file_out);
> > +	struct xfs_inode	*dest = XFS_I(inode_out);
> > +	bool			same_inode = (inode_in == inode_out);
> > +
> > +	xfs_iunlock(dest, XFS_MMAPLOCK_EXCL);
> > +	if (!same_inode)
> > +		xfs_iunlock(src, XFS_MMAPLOCK_SHARED);
> > +	inode_unlock(inode_out);
> > +	if (!same_inode)
> > +		inode_unlock_shared(inode_in);
> > +}
> > +
> >  /*
> > - * Link a range of blocks from one file to another.
> > + * Prepare two files for range cloning.  Upon a successful return both inodes
> > + * will have the iolock and mmaplock held, the page cache of the out file
> > + * will be truncated, and any leases on the out file will have been broken.
> >   */
> > -int
> > -xfs_reflink_remap_range(
> > +STATIC int
> > +xfs_reflink_remap_prep(
> >  	struct file		*file_in,
> >  	loff_t			pos_in,
> >  	struct file		*file_out,
> > @@ -1211,19 +1233,9 @@ xfs_reflink_remap_range(
> >  	struct xfs_inode	*src = XFS_I(inode_in);
> >  	struct inode		*inode_out = file_inode(file_out);
> >  	struct xfs_inode	*dest = XFS_I(inode_out);
> > -	struct xfs_mount	*mp = src->i_mount;
> >  	bool			same_inode = (inode_in == inode_out);
> > -	xfs_fileoff_t		sfsbno, dfsbno;
> > -	xfs_filblks_t		fsblen;
> > -	xfs_extlen_t		cowextsize;
> >  	ssize_t			ret;
> >  
> > -	if (!xfs_sb_version_hasreflink(&mp->m_sb))
> > -		return -EOPNOTSUPP;
> > -
> > -	if (XFS_FORCED_SHUTDOWN(mp))
> > -		return -EIO;
> > -
> >  	/* Lock both files against IO */
> >  	ret = xfs_iolock_two_inodes_and_break_layout(inode_in, inode_out);
> >  	if (ret)
> > @@ -1254,8 +1266,6 @@ xfs_reflink_remap_range(
> >  	if (ret)
> >  		goto out_unlock;
> >  
> > -	trace_xfs_reflink_remap_range(src, pos_in, len, dest, pos_out);
> > -
> >  	/*
> >  	 * Clear out post-eof preallocations because we don't have page cache
> >  	 * backing the delayed allocations and they'll never get freed on
> > @@ -1272,6 +1282,51 @@ xfs_reflink_remap_range(
> >  	if (ret)
> >  		goto out_unlock;
> >  
> > +	/* Zap any page cache for the destination file's range. */
> > +	truncate_inode_pages_range(&inode_out->i_data, pos_out,
> > +				   PAGE_ALIGN(pos_out + len) - 1);
> > +	return 0;
> > +out_unlock:
> > +	xfs_reflink_remap_unlock(file_in, file_out);
> > +	return ret;
> > +}
> > +
> > +/*
> > + * Link a range of blocks from one file to another.
> > + */
> > +int
> > +xfs_reflink_remap_range(
> > +	struct file		*file_in,
> > +	loff_t			pos_in,
> > +	struct file		*file_out,
> > +	loff_t			pos_out,
> > +	u64			len,
> > +	bool			is_dedupe)
> > +{
> > +	struct inode		*inode_in = file_inode(file_in);
> > +	struct xfs_inode	*src = XFS_I(inode_in);
> > +	struct inode		*inode_out = file_inode(file_out);
> > +	struct xfs_inode	*dest = XFS_I(inode_out);
> > +	struct xfs_mount	*mp = src->i_mount;
> > +	xfs_fileoff_t		sfsbno, dfsbno;
> > +	xfs_filblks_t		fsblen;
> > +	xfs_extlen_t		cowextsize;
> > +	ssize_t			ret;
> > +
> > +	if (!xfs_sb_version_hasreflink(&mp->m_sb))
> > +		return -EOPNOTSUPP;
> > +
> > +	if (XFS_FORCED_SHUTDOWN(mp))
> > +		return -EIO;
> > +
> > +	/* Prepare and then clone file data. */
> > +	ret = xfs_reflink_remap_prep(file_in, pos_in, file_out, pos_out,
> > +			len, is_dedupe);
> > +	if (ret)
> > +		return ret;
> > +
> > +	trace_xfs_reflink_remap_range(src, pos_in, len, dest, pos_out);
> > +
> >  	dfsbno = XFS_B_TO_FSBT(mp, pos_out);
> >  	sfsbno = XFS_B_TO_FSBT(mp, pos_in);
> >  	fsblen = XFS_B_TO_FSB(mp, len);
> > @@ -1280,10 +1335,6 @@ xfs_reflink_remap_range(
> >  	if (ret)
> >  		goto out_unlock;
> >  
> > -	/* Zap any page cache for the destination file's range. */
> > -	truncate_inode_pages_range(&inode_out->i_data, pos_out,
> > -				   PAGE_ALIGN(pos_out + len) - 1);
> > -
> >  	/*
> >  	 * Carry the cowextsize hint from src to dest if we're sharing the
> >  	 * entire source file to the entire destination file, the source file
> > @@ -1300,12 +1351,7 @@ xfs_reflink_remap_range(
> >  			is_dedupe);
> >  
> >  out_unlock:
> > -	xfs_iunlock(dest, XFS_MMAPLOCK_EXCL);
> > -	if (!same_inode)
> > -		xfs_iunlock(src, XFS_MMAPLOCK_SHARED);
> > -	inode_unlock(inode_out);
> > -	if (!same_inode)
> > -		inode_unlock_shared(inode_in);
> > +	xfs_reflink_remap_unlock(file_in, file_out);
> >  	if (ret)
> >  		trace_xfs_reflink_remap_range_error(dest, ret, _RET_IP_);
> >  	return ret;
> > 
> > 
> 
> -- 
> Dave Chinner
> david@fromorbit.com