Re: [PATCH] xfs: only reclaim unwritten COW extents periodically

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On Mon, Feb 27, 2017 at 09:26:51PM -0800, Darrick J. Wong wrote:
> On Mon, Feb 27, 2017 at 04:49:10PM -0800, Christoph Hellwig wrote:
> > We only want to reclaim preallocations from our periodic work item.
> > Currenrly this is archived by looking for a diry inode, but that check
> > is rather fragile.  Instead add flags to the xfs_reflink_cancel_cow_* so
> > that the caller can ask for just cancelling unwritten extents in the COw
> > fork.
> > 
> > Signed-off-by: Christoph Hellwig <hch@xxxxxx>
> > ---
> >  fs/xfs/xfs_aops.c    |  2 +-
> >  fs/xfs/xfs_icache.c  |  2 +-
> >  fs/xfs/xfs_inode.c   |  2 +-
> >  fs/xfs/xfs_reflink.c | 14 +++++++++-----
> >  fs/xfs/xfs_reflink.h |  5 +++--
> >  fs/xfs/xfs_super.c   |  2 +-
> >  6 files changed, 16 insertions(+), 11 deletions(-)
> > 
> > diff --git a/fs/xfs/xfs_aops.c b/fs/xfs/xfs_aops.c
> > index b480647e00e7..290c0fb306e7 100644
> > --- a/fs/xfs/xfs_aops.c
> > +++ b/fs/xfs/xfs_aops.c
> > @@ -293,7 +293,7 @@ xfs_end_io(
> >  			goto done;
> >  		if (ioend->io_bio->bi_error) {
> >  			error = xfs_reflink_cancel_cow_range(ip,
> > -					ioend->io_offset, ioend->io_size);
> > +					ioend->io_offset, ioend->io_size, 0);
> >  			goto done;
> >  		}
> >  		error = xfs_reflink_end_cow(ip, ioend->io_offset,
> > diff --git a/fs/xfs/xfs_icache.c b/fs/xfs/xfs_icache.c
> > index 7234b9748c36..1f7d158266c1 100644
> > --- a/fs/xfs/xfs_icache.c
> > +++ b/fs/xfs/xfs_icache.c
> > @@ -1608,7 +1608,7 @@ xfs_inode_free_cowblocks(
> >  	xfs_ilock(ip, XFS_IOLOCK_EXCL);
> >  	xfs_ilock(ip, XFS_MMAPLOCK_EXCL);
> >  
> > -	ret = xfs_reflink_cancel_cow_range(ip, 0, NULLFILEOFF);
> > +	ret = xfs_reflink_cancel_cow_range(ip, 0, NULLFILEOFF, XFS_CC_UNWRITTEN);
> 
> Ok, so the periodic work item leaves real cow extents alone now, which
> is good since real extents now represent pending cow operations.  Good.
> 
> >  	xfs_iunlock(ip, XFS_MMAPLOCK_EXCL);
> >  	xfs_iunlock(ip, XFS_IOLOCK_EXCL);
> > diff --git a/fs/xfs/xfs_inode.c b/fs/xfs/xfs_inode.c
> > index edfa6a55b064..164e74a511b1 100644
> > --- a/fs/xfs/xfs_inode.c
> > +++ b/fs/xfs/xfs_inode.c
> > @@ -1615,7 +1615,7 @@ xfs_itruncate_extents(
> >  
> >  	/* Remove all pending CoW reservations. */
> >  	error = xfs_reflink_cancel_cow_blocks(ip, &tp, first_unmap_block,
> > -			last_block);
> > +			last_block, 0);
> >  	if (error)
> >  		goto out;
> >  
> > diff --git a/fs/xfs/xfs_reflink.c b/fs/xfs/xfs_reflink.c
> > index 08ca9f81b087..83605af3b135 100644
> > --- a/fs/xfs/xfs_reflink.c
> > +++ b/fs/xfs/xfs_reflink.c
> > @@ -551,7 +551,8 @@ xfs_reflink_cancel_cow_blocks(
> >  	struct xfs_inode		*ip,
> >  	struct xfs_trans		**tpp,
> >  	xfs_fileoff_t			offset_fsb,
> > -	xfs_fileoff_t			end_fsb)
> > +	xfs_fileoff_t			end_fsb,
> > +	unsigned			flags)
> >  {
> >  	struct xfs_ifork		*ifp = XFS_IFORK_PTR(ip, XFS_COW_FORK);
> >  	struct xfs_bmbt_irec		got, del;
> > @@ -575,7 +576,8 @@ xfs_reflink_cancel_cow_blocks(
> >  					&idx, &got, &del);
> >  			if (error)
> >  				break;
> > -		} else {
> > +		} else if (del.br_state == XFS_EXT_UNWRITTEN ||
> > +			   !(flags & XFS_CC_UNWRITTEN)) {
> >  			xfs_trans_ijoin(*tpp, ip, 0);
> >  			xfs_defer_init(&dfops, &firstfsb);
> >  
> > @@ -623,7 +625,8 @@ int
> >  xfs_reflink_cancel_cow_range(
> >  	struct xfs_inode	*ip,
> >  	xfs_off_t		offset,
> > -	xfs_off_t		count)
> > +	xfs_off_t		count,
> > +	unsigned		flags)
> >  {
> >  	struct xfs_trans	*tp;
> >  	xfs_fileoff_t		offset_fsb;
> > @@ -649,7 +652,8 @@ xfs_reflink_cancel_cow_range(
> >  	xfs_trans_ijoin(tp, ip, 0);
> >  
> >  	/* Scrape out the old CoW reservations */
> > -	error = xfs_reflink_cancel_cow_blocks(ip, &tp, offset_fsb, end_fsb);
> > +	error = xfs_reflink_cancel_cow_blocks(ip, &tp, offset_fsb, end_fsb,
> > +			flags);
> >  	if (error)
> >  		goto out_cancel;
> >  
> > @@ -1437,7 +1441,7 @@ xfs_reflink_clear_inode_flag(
> >  	 * We didn't find any shared blocks so turn off the reflink flag.
> >  	 * First, get rid of any leftover CoW mappings.
> >  	 */
> > -	error = xfs_reflink_cancel_cow_blocks(ip, tpp, 0, NULLFILEOFF);
> > +	error = xfs_reflink_cancel_cow_blocks(ip, tpp, 0, NULLFILEOFF, 0);
> >  	if (error)
> >  		return error;
> >  
> > diff --git a/fs/xfs/xfs_reflink.h b/fs/xfs/xfs_reflink.h
> > index 33ac9b8db683..9416279b3c89 100644
> > --- a/fs/xfs/xfs_reflink.h
> > +++ b/fs/xfs/xfs_reflink.h
> > @@ -37,11 +37,12 @@ extern bool xfs_reflink_find_cow_mapping(struct xfs_inode *ip, xfs_off_t offset,
> >  extern void xfs_reflink_trim_irec_to_next_cow(struct xfs_inode *ip,
> >  		xfs_fileoff_t offset_fsb, struct xfs_bmbt_irec *imap);
> >  
> > +#define XFS_CC_UNWRITTEN	0x01
> 
> Could we have a comment here about what CC_UNWRITTEN means?
> 
> I /think/ it means "don't remove real extents", since when it's specified
> delalloc reservations still get removed by _reflink_cancel_cow_*, correct?
> 
> Somewhere we ought to record the fact that flags == 0 removes everything.

It's been a week; ping?  (Or: did anyone receive this reply at all?)

--D

> 
> --D
> 
> >  extern int xfs_reflink_cancel_cow_blocks(struct xfs_inode *ip,
> >  		struct xfs_trans **tpp, xfs_fileoff_t offset_fsb,
> > -		xfs_fileoff_t end_fsb);
> > +		xfs_fileoff_t end_fsb, unsigned flags);
> >  extern int xfs_reflink_cancel_cow_range(struct xfs_inode *ip, xfs_off_t offset,
> > -		xfs_off_t count);
> > +		xfs_off_t count, unsigned flags);
> >  extern int xfs_reflink_end_cow(struct xfs_inode *ip, xfs_off_t offset,
> >  		xfs_off_t count);
> >  extern int xfs_reflink_recover_cow(struct xfs_mount *mp);
> > diff --git a/fs/xfs/xfs_super.c b/fs/xfs/xfs_super.c
> > index 890862f2447c..9136854030d5 100644
> > --- a/fs/xfs/xfs_super.c
> > +++ b/fs/xfs/xfs_super.c
> > @@ -953,7 +953,7 @@ xfs_fs_destroy_inode(
> >  	XFS_STATS_INC(ip->i_mount, vn_remove);
> >  
> >  	if (xfs_is_reflink_inode(ip)) {
> > -		error = xfs_reflink_cancel_cow_range(ip, 0, NULLFILEOFF);
> > +		error = xfs_reflink_cancel_cow_range(ip, 0, NULLFILEOFF, 0);
> >  		if (error && !XFS_FORCED_SHUTDOWN(ip->i_mount))
> >  			xfs_warn(ip->i_mount,
> >  "Error %d while evicting CoW blocks for inode %llu.",
> > -- 
> > 2.11.0
> > 
> > --
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