Commit 350a27a6 authored by Darrick J. Wong's avatar Darrick J. Wong
Browse files

xfs: introduce reflink utility functions 



These functions will be used by the other reflink functions to find
the maximum length of a range of shared blocks.

Signed-off-by: default avatarDarrick J. Wong <darrick.wong@oracle.coM>
Reviewed-by: default avatarChristoph Hellwig <hch@lst.de>
parent d0e853f3

fs/xfs/libxfs/xfs_refcount.c

+102 −0
Original line number Diff line number Diff line
@@ -1163,3 +1163,105 @@ xfs_refcount_decrease_extent( 
	return __xfs_refcount_add(mp, dfops, XFS_REFCOUNT_DECREASE,

			PREV->br_startblock, PREV->br_blockcount);

}



/*

 * Given an AG extent, find the lowest-numbered run of shared blocks

 * within that range and return the range in fbno/flen.  If

 * find_end_of_shared is set, return the longest contiguous extent of

 * shared blocks; if not, just return the first extent we find.  If no

 * shared blocks are found, fbno and flen will be set to NULLAGBLOCK

 * and 0, respectively.

 */

int

xfs_refcount_find_shared(

	struct xfs_btree_cur		*cur,

	xfs_agblock_t			agbno,

	xfs_extlen_t			aglen,

	xfs_agblock_t			*fbno,

	xfs_extlen_t			*flen,

	bool				find_end_of_shared)

{

	struct xfs_refcount_irec	tmp;

	int				i;

	int				have;

	int				error;



	trace_xfs_refcount_find_shared(cur->bc_mp, cur->bc_private.a.agno,

			agbno, aglen);



	/* By default, skip the whole range */

	*fbno = NULLAGBLOCK;

	*flen = 0;



	/* Try to find a refcount extent that crosses the start */

	error = xfs_refcount_lookup_le(cur, agbno, &have);

	if (error)

		goto out_error;

	if (!have) {

		/* No left extent, look at the next one */

		error = xfs_btree_increment(cur, 0, &have);

		if (error)

			goto out_error;

		if (!have)

			goto done;

	}

	error = xfs_refcount_get_rec(cur, &tmp, &i);

	if (error)

		goto out_error;

	XFS_WANT_CORRUPTED_GOTO(cur->bc_mp, i == 1, out_error);



	/* If the extent ends before the start, look at the next one */

	if (tmp.rc_startblock + tmp.rc_blockcount <= agbno) {

		error = xfs_btree_increment(cur, 0, &have);

		if (error)

			goto out_error;

		if (!have)

			goto done;

		error = xfs_refcount_get_rec(cur, &tmp, &i);

		if (error)

			goto out_error;

		XFS_WANT_CORRUPTED_GOTO(cur->bc_mp, i == 1, out_error);

	}



	/* If the extent starts after the range we want, bail out */

	if (tmp.rc_startblock >= agbno + aglen)

		goto done;



	/* We found the start of a shared extent! */

	if (tmp.rc_startblock < agbno) {

		tmp.rc_blockcount -= (agbno - tmp.rc_startblock);

		tmp.rc_startblock = agbno;

	}



	*fbno = tmp.rc_startblock;

	*flen = min(tmp.rc_blockcount, agbno + aglen - *fbno);

	if (!find_end_of_shared)

		goto done;



	/* Otherwise, find the end of this shared extent */

	while (*fbno + *flen < agbno + aglen) {

		error = xfs_btree_increment(cur, 0, &have);

		if (error)

			goto out_error;

		if (!have)

			break;

		error = xfs_refcount_get_rec(cur, &tmp, &i);

		if (error)

			goto out_error;

		XFS_WANT_CORRUPTED_GOTO(cur->bc_mp, i == 1, out_error);

		if (tmp.rc_startblock >= agbno + aglen ||

		    tmp.rc_startblock != *fbno + *flen)

			break;

		*flen = min(*flen + tmp.rc_blockcount, agbno + aglen - *fbno);

	}



done:

	trace_xfs_refcount_find_shared_result(cur->bc_mp,

			cur->bc_private.a.agno, *fbno, *flen);



out_error:

	if (error)

		trace_xfs_refcount_find_shared_error(cur->bc_mp,

				cur->bc_private.a.agno, error, _RET_IP_);

	return error;

}

fs/xfs/libxfs/xfs_refcount.h

+4 −0
Original line number Diff line number Diff line
@@ -54,4 +54,8 @@ extern int xfs_refcount_finish_one(struct xfs_trans *tp, 
		xfs_fsblock_t *new_fsb, xfs_extlen_t *new_len,

		struct xfs_btree_cur **pcur);



extern int xfs_refcount_find_shared(struct xfs_btree_cur *cur,

		xfs_agblock_t agbno, xfs_extlen_t aglen, xfs_agblock_t *fbno,

		xfs_extlen_t *flen, bool find_end_of_shared);



#endif	/* __XFS_REFCOUNT_H__ */