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From: Brian Foster <bfoster@redhat.com>
To: Christoph Hellwig <hch@lst.de>
Cc: linux-xfs@vger.kernel.org, linux-fsdevel@vger.kernel.org,
	linux-mm@kvack.org
Subject: Re: [PATCH 19/34] xfs: simplify xfs_bmap_punch_delalloc_range
Date: Wed, 23 May 2018 12:17:11 -0400	[thread overview]
Message-ID: <20180523161710.GA33498@bfoster.bfoster> (raw)
In-Reply-To: <20180523144357.18985-20-hch@lst.de>

On Wed, May 23, 2018 at 04:43:42PM +0200, Christoph Hellwig wrote:
> Instead of using xfs_bmapi_read to find delalloc extents and then punch
> them out using xfs_bunmapi, opencode the loop to iterate over the extents
> and call xfs_bmap_del_extent_delay directly.  This both simplifies the
> code and reduces the number of extent tree lookups required.
> 
> Signed-off-by: Christoph Hellwig <hch@lst.de>
> ---
>  fs/xfs/xfs_bmap_util.c | 78 ++++++++++++++----------------------------
>  1 file changed, 25 insertions(+), 53 deletions(-)
> 
> diff --git a/fs/xfs/xfs_bmap_util.c b/fs/xfs/xfs_bmap_util.c
> index 06badcbadeb4..c009bdf9fdce 100644
> --- a/fs/xfs/xfs_bmap_util.c
> +++ b/fs/xfs/xfs_bmap_util.c
...
> @@ -708,63 +706,37 @@ xfs_bmap_punch_delalloc_range(
>  	xfs_fileoff_t		start_fsb,
>  	xfs_fileoff_t		length)
>  {
> -	xfs_fileoff_t		remaining = length;
> +	struct xfs_ifork	*ifp = &ip->i_df;
> +	struct xfs_bmbt_irec	got, del;
> +	struct xfs_iext_cursor	icur;
>  	int			error = 0;
>  
>  	ASSERT(xfs_isilocked(ip, XFS_ILOCK_EXCL));
>  
> -	do {
> -		int		done;
> -		xfs_bmbt_irec_t	imap;
> -		int		nimaps = 1;
> -		xfs_fsblock_t	firstblock;
> -		struct xfs_defer_ops dfops;
> +	if (!(ifp->if_flags & XFS_IFEXTENTS)) {
> +		error = xfs_iread_extents(NULL, ip, XFS_DATA_FORK);
> +		if (error)
> +			return error;
> +	}
>  
> -		/*
> -		 * Map the range first and check that it is a delalloc extent
> -		 * before trying to unmap the range. Otherwise we will be
> -		 * trying to remove a real extent (which requires a
> -		 * transaction) or a hole, which is probably a bad idea...
> -		 */
> -		error = xfs_bmapi_read(ip, start_fsb, 1, &imap, &nimaps,
> -				       XFS_BMAPI_ENTIRE);
> +	if (!xfs_iext_lookup_extent(ip, ifp, start_fsb, &icur, &got))
> +		return 0;
>  
> -		if (error) {
> -			/* something screwed, just bail */
> -			if (!XFS_FORCED_SHUTDOWN(ip->i_mount)) {
> -				xfs_alert(ip->i_mount,
> -			"Failed delalloc mapping lookup ino %lld fsb %lld.",
> -						ip->i_ino, start_fsb);
> -			}
> +	do {
> +		if (got.br_startoff >= start_fsb + length)
>  			break;
> -		}
> -		if (!nimaps) {
> -			/* nothing there */
> -			goto next_block;
> -		}
> -		if (imap.br_startblock != DELAYSTARTBLOCK) {
> -			/* been converted, ignore */
> -			goto next_block;
> -		}
> -		WARN_ON(imap.br_blockcount == 0);
> +		if (!isnullstartblock(got.br_startblock))
> +			continue;
>  
> -		/*
> -		 * Note: while we initialise the firstblock/dfops pair, they
> -		 * should never be used because blocks should never be
> -		 * allocated or freed for a delalloc extent and hence we need
> -		 * don't cancel or finish them after the xfs_bunmapi() call.
> -		 */
> -		xfs_defer_init(&dfops, &firstblock);
> -		error = xfs_bunmapi(NULL, ip, start_fsb, 1, 0, 1, &firstblock,
> -					&dfops, &done);
> +		del = got;
> +		xfs_trim_extent(&del, start_fsb, length);
> +		error = xfs_bmap_del_extent_delay(ip, XFS_DATA_FORK, &icur,
> +				&got, &del);
>  		if (error)
>  			break;
> -
> -		ASSERT(!xfs_defer_has_unfinished_work(&dfops));
> -next_block:
> -		start_fsb++;
> -		remaining--;
> -	} while(remaining > 0);
> +		if (!xfs_iext_get_extent(ifp, &icur, &got))
> +			break;

Mostly looks Ok, but I'm not following what this get_extent() call is
for..? It also doesn't look like it would always do the right thing with
sub-page blocks. Consider a page with a couple discontig delalloc blocks
that happen to be the first extents in the file. The first
xfs_bmap_del_extent_delay() would do:

	xfs_iext_remove(ip, icur, state);
	xfs_iext_prev(ifp, icur);

... which I think sets cur->pos to -1, causes the get_extent() to fail
and thus fails to remove the subsequent delalloc blocks. Hm?

Brian

> +	} while (xfs_iext_next_extent(ifp, &icur, &got));
>  
>  	return error;
>  }
> -- 
> 2.17.0
> 
> --
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  reply	other threads:[~2018-05-23 16:17 UTC|newest]

Thread overview: 75+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2018-05-23 14:43 buffered I/O without buffer heads in xfs and iomap v3 Christoph Hellwig
2018-05-23 14:43 ` [PATCH 01/34] block: add a lower-level bio_add_page interface Christoph Hellwig
2018-05-30  5:28   ` Darrick J. Wong
2018-05-23 14:43 ` [PATCH 02/34] fs: factor out a __generic_write_end helper Christoph Hellwig
2018-05-30  5:30   ` Darrick J. Wong
2018-05-23 14:43 ` [PATCH 03/34] fs: move page_cache_seek_hole_data to iomap.c Christoph Hellwig
2018-05-30  5:31   ` Darrick J. Wong
2018-05-23 14:43 ` [PATCH 04/34] fs: remove the buffer_unwritten check in page_seek_hole_data Christoph Hellwig
2018-05-30  5:36   ` Darrick J. Wong
2018-05-23 14:43 ` [PATCH 05/34] fs: use ->is_partially_uptodate in page_cache_seek_hole_data Christoph Hellwig
2018-05-30  5:41   ` Darrick J. Wong
2018-05-23 14:43 ` [PATCH 06/34] mm: give the 'ret' variable a better name __do_page_cache_readahead Christoph Hellwig
2018-05-30  5:42   ` Darrick J. Wong
2018-05-23 14:43 ` [PATCH 07/34] mm: return an unsigned int from __do_page_cache_readahead Christoph Hellwig
2018-05-30  5:44   ` Darrick J. Wong
2018-05-23 14:43 ` [PATCH 08/34] mm: split ->readpages calls to avoid non-contiguous pages lists Christoph Hellwig
2018-05-30  5:46   ` Darrick J. Wong
2018-05-23 14:43 ` [PATCH 09/34] iomap: inline data should be an iomap type, not a flag Christoph Hellwig
2018-05-30  5:49   ` Darrick J. Wong
2018-05-23 14:43 ` [PATCH 10/34] iomap: fix the comment describing IOMAP_NOWAIT Christoph Hellwig
2018-05-30  5:49   ` Darrick J. Wong
2018-05-23 14:43 ` [PATCH 11/34] iomap: move IOMAP_F_BOUNDARY to gfs2 Christoph Hellwig
2018-05-30  5:50   ` Darrick J. Wong
2018-05-30  9:30     ` [Cluster-devel] " Steven Whitehouse
2018-05-30  9:59       ` Christoph Hellwig
2018-05-30 10:02         ` Steven Whitehouse
2018-05-30 10:10           ` Christoph Hellwig
2018-05-30 10:12             ` Steven Whitehouse
2018-05-30 11:03               ` Andreas Gruenbacher
2018-05-23 14:43 ` [PATCH 12/34] iomap: use __bio_add_page in iomap_dio_zero Christoph Hellwig
2018-05-30  5:51   ` Darrick J. Wong
2018-05-23 14:43 ` [PATCH 13/34] iomap: add a iomap_sector helper Christoph Hellwig
2018-05-30  5:52   ` Darrick J. Wong
2018-05-23 14:43 ` [PATCH 14/34] iomap: add an iomap-based bmap implementation Christoph Hellwig
2018-05-30  5:54   ` Darrick J. Wong
2018-05-23 14:43 ` [PATCH 15/34] iomap: add an iomap-based readpage and readpages implementation Christoph Hellwig
2018-05-30  6:11   ` Darrick J. Wong
2018-05-30  6:23     ` Christoph Hellwig
2018-05-23 14:43 ` [PATCH 16/34] iomap: add initial support for writes without buffer heads Christoph Hellwig
2018-05-30  6:21   ` Darrick J. Wong
2018-05-23 14:43 ` [PATCH 17/34] xfs: use iomap_bmap Christoph Hellwig
2018-05-30  6:14   ` Darrick J. Wong
2018-05-23 14:43 ` [PATCH 18/34] xfs: use iomap for blocksize == PAGE_SIZE readpage and readpages Christoph Hellwig
2018-05-30  6:22   ` Darrick J. Wong
2018-05-23 14:43 ` [PATCH 19/34] xfs: simplify xfs_bmap_punch_delalloc_range Christoph Hellwig
2018-05-23 16:17   ` Brian Foster [this message]
2018-05-24  8:01     ` Christoph Hellwig
2018-05-23 14:43 ` [PATCH 20/34] xfs: simplify xfs_aops_discard_page Christoph Hellwig
2018-05-23 14:43 ` [PATCH 21/34] xfs: move locking into xfs_bmap_punch_delalloc_range Christoph Hellwig
2018-05-23 14:43 ` [PATCH 22/34] xfs: make xfs_writepage_map extent map centric Christoph Hellwig
2018-05-24 14:59   ` Brian Foster
2018-05-24 16:53     ` Christoph Hellwig
2018-05-24 18:13       ` Brian Foster
2018-05-25  6:19         ` Christoph Hellwig
2018-05-25 11:35           ` Brian Foster
2018-05-28  7:15             ` Christoph Hellwig
2018-05-29 11:26               ` Brian Foster
2018-05-29 13:08                 ` Christoph Hellwig
2018-05-29 17:04                   ` Brian Foster
2018-05-23 14:43 ` [PATCH 23/34] xfs: remove the now unused XFS_BMAPI_IGSTATE flag Christoph Hellwig
2018-05-23 14:43 ` [PATCH 24/34] xfs: remove xfs_reflink_find_cow_mapping Christoph Hellwig
2018-05-23 14:43 ` [PATCH 25/34] xfs: remove xfs_reflink_trim_irec_to_next_cow Christoph Hellwig
2018-05-24 14:59   ` Brian Foster
2018-05-24 15:06     ` Brian Foster
2018-05-24 17:10       ` Christoph Hellwig
2018-05-23 14:43 ` [PATCH 26/34] xfs: simplify xfs_map_blocks by using xfs_iext_lookup_extent directly Christoph Hellwig
2018-05-23 14:43 ` [PATCH 27/34] xfs: don't clear imap_valid for a non-uptodate buffers Christoph Hellwig
2018-05-23 14:43 ` [PATCH 28/34] xfs: remove the imap_valid flag Christoph Hellwig
2018-05-23 14:43 ` [PATCH 29/34] xfs: don't look at buffer heads in xfs_add_to_ioend Christoph Hellwig
2018-05-23 14:43 ` [PATCH 30/34] xfs: move all writeback buffer_head manipulation into xfs_map_at_offset Christoph Hellwig
2018-05-23 14:43 ` [PATCH 31/34] xfs: remove xfs_start_page_writeback Christoph Hellwig
2018-05-23 14:43 ` [PATCH 32/34] xfs: refactor the tail of xfs_writepage_map Christoph Hellwig
2018-05-23 14:43 ` [PATCH 33/34] xfs: do not set the page uptodate in xfs_writepage_map Christoph Hellwig
2018-05-23 14:43 ` [PATCH 34/34] xfs: allow writeback on pages without buffer heads Christoph Hellwig
  -- strict thread matches above, loose matches on Subject: below --
2018-05-18 16:47 buffered I/O without buffer heads in xfs and iomap v2 Christoph Hellwig
2018-05-18 16:48 ` [PATCH 19/34] xfs: simplify xfs_bmap_punch_delalloc_range Christoph Hellwig

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