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Commit a14234c7 authored by Christoph Hellwig's avatar Christoph Hellwig Committed by Darrick J. Wong
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xfs: go straight to real allocations for direct I/O COW writes 



When we allocate COW fork blocks for direct I/O writes we currently first
create a delayed allocation, and then convert it to a real allocation
once we've got the delayed one.

As there is no good reason for that this patch instead makes use call
xfs_bmapi_write from the COW allocation path.  The only interesting bits
are a few tweaks the low-level allocator to allow for this, most notably
the need to remove the call to xfs_bmap_extsize_align for the cowextsize
in xfs_bmap_btalloc - for the existing convert case it's a no-op, but
for the direct allocation case it would blow up our block reservation
way beyond what we reserved for the transaction.

Signed-off-by: default avatarChristoph Hellwig <hch@lst.de>
Reviewed-by: default avatarDarrick J. Wong <darrick.wong@oracle.com>
Signed-off-by: default avatarDarrick J. Wong <darrick.wong@oracle.com>
parent dcf9585a

fs/xfs/libxfs/xfs_bmap.c

+2 −1
Original line number Diff line number Diff line
@@ -2895,13 +2895,14 @@ xfs_bmap_add_extent_hole_real( 
	ASSERT(!isnullstartblock(new->br_startblock));

	ASSERT(!bma->cur ||

	       !(bma->cur->bc_private.b.flags & XFS_BTCUR_BPRV_WASDEL));

	ASSERT(whichfork != XFS_COW_FORK);



	XFS_STATS_INC(mp, xs_add_exlist);



	state = 0;

	if (whichfork == XFS_ATTR_FORK)

		state |= BMAP_ATTRFORK;

	if (whichfork == XFS_COW_FORK)

		state |= BMAP_COWFORK;



	/*

	 * Check and set flags if this segment has a left neighbor.

fs/xfs/xfs_reflink.c

+66 −28
Original line number Diff line number Diff line
@@ -389,32 +389,51 @@ __xfs_reflink_allocate_cow( 
	xfs_fileoff_t		end_fsb)

{

	struct xfs_mount	*mp = ip->i_mount;

	struct xfs_bmbt_irec	imap;

	struct xfs_bmbt_irec	imap, got;

	struct xfs_defer_ops	dfops;

	struct xfs_trans	*tp;

	xfs_fsblock_t		first_block;

	int			nimaps = 1, error;

	bool			shared;

	int			nimaps, error, lockmode;

	bool			shared, trimmed;

	xfs_filblks_t		resaligned;

	xfs_extlen_t		resblks;

	xfs_extnum_t		idx;



	xfs_defer_init(&dfops, &first_block);

	resaligned = xfs_aligned_fsb_count(*offset_fsb, end_fsb - *offset_fsb,

			xfs_get_cowextsz_hint(ip));

	resblks = XFS_DIOSTRAT_SPACE_RES(mp, resaligned);



	error = xfs_trans_alloc(mp, &M_RES(mp)->tr_write, 0, 0,

			XFS_TRANS_RESERVE, &tp);

	error = xfs_trans_alloc(mp, &M_RES(mp)->tr_write, resblks, 0, 0, &tp);

	if (error)

		return error;



	xfs_ilock(ip, XFS_ILOCK_EXCL);

	lockmode = XFS_ILOCK_EXCL;

	xfs_ilock(ip, lockmode);



	/* Read extent from the source file. */

	/*

	 * Even if the extent is not shared we might have a preallocation for

	 * it in the COW fork.  If so use it.

	 */

	if (xfs_iext_lookup_extent(ip, ip->i_cowfp, *offset_fsb, &idx, &got) &&

	    got.br_startoff <= *offset_fsb) {

		/* If we have a real allocation in the COW fork we're done. */

		if (!isnullstartblock(got.br_startblock)) {

			xfs_trim_extent(&got, *offset_fsb,

					end_fsb - *offset_fsb);

			*offset_fsb = got.br_startoff + got.br_blockcount;

			goto out_trans_cancel;

		}

	} else {

		nimaps = 1;

		error = xfs_bmapi_read(ip, *offset_fsb, end_fsb - *offset_fsb,

				&imap, &nimaps, 0);

		if (error)

		goto out_unlock;

			goto out_trans_cancel;

		ASSERT(nimaps == 1);



	/* Make sure there's a CoW reservation for it. */

	error = xfs_reflink_reserve_cow(ip, &imap, &shared);

		/* Trim the mapping to the nearest shared extent boundary. */

		error = xfs_reflink_trim_around_shared(ip, &imap, &shared,

				&trimmed);

		if (error)

			goto out_trans_cancel;
@@ -423,28 +442,47 @@ __xfs_reflink_allocate_cow( 
			goto out_trans_cancel;

		}



	/* Allocate the entire reservation as unwritten blocks. */

		*offset_fsb = imap.br_startoff;

		end_fsb = imap.br_startoff + imap.br_blockcount;

	}



	error = xfs_trans_reserve_quota_nblks(tp, ip, resblks, 0,

			XFS_QMOPT_RES_REGBLKS);

	if (error)

		goto out_trans_cancel;



	xfs_trans_ijoin(tp, ip, 0);

	error = xfs_bmapi_write(tp, ip, imap.br_startoff, imap.br_blockcount,



	xfs_defer_init(&dfops, &first_block);

	nimaps = 1;



	/* Allocate the entire reservation as unwritten blocks. */

	error = xfs_bmapi_write(tp, ip, *offset_fsb, end_fsb - *offset_fsb,

			XFS_BMAPI_COWFORK | XFS_BMAPI_PREALLOC, &first_block,

			XFS_EXTENTADD_SPACE_RES(mp, XFS_DATA_FORK),

			&imap, &nimaps, &dfops);

			resblks, &imap, &nimaps, &dfops);

	if (error)

		goto out_trans_cancel;

		goto out_bmap_cancel;



	/* Finish up. */

	error = xfs_defer_finish(&tp, &dfops, NULL);

	if (error)

		goto out_trans_cancel;

		goto out_bmap_cancel;



	error = xfs_trans_commit(tp);

	if (error)

		goto out_unlock;



	*offset_fsb = imap.br_startoff + imap.br_blockcount;



out_unlock:

	xfs_iunlock(ip, XFS_ILOCK_EXCL);

	xfs_iunlock(ip, lockmode);

	return error;

out_trans_cancel:



out_bmap_cancel:

	xfs_defer_cancel(&dfops);

	xfs_trans_unreserve_quota_nblks(tp, ip, (long)resblks, 0,

			XFS_QMOPT_RES_REGBLKS);

out_trans_cancel:

	xfs_trans_cancel(tp);

	goto out_unlock;

}