Re: [PATCH 40/58] libxfs: adjust refcount of an extent of blocks in refcount btree

Darrick J. Wong
2015-10-27T19:05:45Z

On Tue, Oct 06, 2015 at 09:59:33PM -0700, Darrick J. Wong wrote:
> Provide functions to adjust the reference counts for an extent of
> physical blocks stored in the refcount btree.
>
> Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
> ---
> fs/xfs/libxfs/xfs_refcount.c | 771 ++++++++++++++++++++++++++++++++++++++++++
> fs/xfs/libxfs/xfs_refcount.h | 8
> 2 files changed, 779 insertions(+)
>
>
> diff --git a/fs/xfs/libxfs/xfs_refcount.c b/fs/xfs/libxfs/xfs_refcount.c
> index b3f2c25..02892bc 100644
> --- a/fs/xfs/libxfs/xfs_refcount.c
> +++ b/fs/xfs/libxfs/xfs_refcount.c
> @@ -167,3 +167,774 @@ xfs_refcountbt_delete(
> out_error:
> return error;
> }
> +
> +/*
> + * Adjusting the Reference Count
> + *
> + * As stated elsewhere, the reference count btree (refcbt) stores
> + * >1 reference counts for extents of physical blocks. In this
> + * operation, we're either raising or lowering the reference count of
> + * some subrange stored in the tree:
> + *
> + * <------ adjustment range ------>
> + * ----+ +---+-----+ +--+--------+---------
> + * 2 | | 3 | 4 | |17| 55 | 10
> + * ----+ +---+-----+ +--+--------+---------
> + * X axis is physical blocks number;
> + * reference counts are the numbers inside the rectangles
> + *
> + * The first thing we need to do is to ensure that there are no
> + * refcount extents crossing either boundary of the range to be
> + * adjusted. For any extent that does cross a boundary, split it into
> + * two extents so that we can increment the refcount of one of the
> + * pieces later:
> + *
> + * <------ adjustment range ------>
> + * ----+ +---+-----+ +--+--------+----+----
> + * 2 | | 3 | 2 | |17| 55 | 10 | 10
> + * ----+ +---+-----+ +--+--------+----+----
> + *
> + * For this next step, let's assume that all the physical blocks in
> + * the adjustment range are mapped to a file and are therefore in use
> + * at least once. Therefore, we can infer that any gap in the
> + * refcount tree within the adjustment range represents a physical
> + * extent with refcount == 1:
> + *
> + * <------ adjustment range ------>
> + * ----+---+---+-----+-+--+--------+----+----
> + * 2 |"1"| 3 | 2 |1|17| 55 | 10 | 10
> + * ----+---+---+-----+-+--+--------+----+----
> + * ^
> + *
> + * For each extent that falls within the interval range, figure out
> + * which extent is to the left or the right of that extent. Now we
> + * have a left, current, and right extent. If the new reference count
> + * of the center extent enables us to merge left, center, and right
> + * into one record covering all three, do so. If the center extent is
> + * at the left end of the range, abuts the left extent, and its new
> + * reference count matches the left extent's record, then merge them.
> + * If the center extent is at the right end of the range, abuts the
> + * right extent, and the reference counts match, merge those. In the
> + * example, we can left merge (assuming an increment operation):
> + *
> + * <------ adjustment range ------>
> + * --------+---+-----+-+--+--------+----+----
> + * 2 | 3 | 2 |1|17| 55 | 10 | 10
> + * --------+---+-----+-+--+--------+----+----
> + * ^
> + *
> + * For all other extents within the range, adjust the reference count
> + * or delete it if the refcount falls below 2. If we were
> + * incrementing, the end result looks like this:
> + *
> + * <------ adjustment range ------>
> + * --------+---+-----+-+--+--------+----+----
> + * 2 | 4 | 3 |2|18| 56 | 11 | 10
> + * --------+---+-----+-+--+--------+----+----
> + *
> + * The result of a decrement operation looks as such:
> + *
> + * <------ adjustment range ------>
> + * ----+ +---+ +--+--------+----+----
> + * 2 | | 2 | |16| 54 | 9 | 10
> + * ----+ +---+ +--+--------+----+----
> + * DDDD 111111DD
> + *
> + * The blocks marked "D" are freed; the blocks marked "1" are only
> + * referenced once and therefore the record is removed from the
> + * refcount btree.
> + */
> +
> +#define RLNEXT(rl) ((rl).rc_startblock + (rl).rc_blockcount)
> +/*
> + * Split a left rlextent that crosses agbno.
> + */
> +STATIC int
> +try_split_left_rlextent(
> + struct xfs_btree_cur *cur,
> + xfs_agblock_t agbno)
> +{
> + struct xfs_refcount_irec left, tmp;
> + int found_rec;
> + int error;
> +
> + error = xfs_refcountbt_lookup_le(cur, agbno, &found_rec);
> + if (error)
> + goto out_error;
> + if (!found_rec)
> + return 0;
> +
> + error = xfs_refcountbt_get_rec(cur, &left, &found_rec);
> + if (error)
> + goto out_error;
> + XFS_WANT_CORRUPTED_GOTO(cur->bc_mp, found_rec == 1, out_error);
> + if (left.rc_startblock >= agbno || RLNEXT(left) <= agbno)
> + return 0;
> +
> + trace_xfs_refcount_split_left_extent(cur->bc_mp, cur->bc_private.a.agno,
> + &left, agbno);
> + tmp = left;
> + tmp.rc_blockcount = agbno - left.rc_startblock;
> + error = xfs_refcountbt_update(cur, &tmp);
> + if (error)
> + goto out_error;
> +
> + error = xfs_btree_increment(cur, 0, &found_rec);
> + if (error)
> + goto out_error;
> +
> + tmp = left;
> + tmp.rc_startblock = agbno;
> + tmp.rc_blockcount -= (agbno - left.rc_startblock);
> + error = xfs_refcountbt_insert(cur, &tmp, &found_rec);
> + if (error)
> + goto out_error;
> + XFS_WANT_CORRUPTED_GOTO(cur->bc_mp, found_rec == 1, out_error);
> + return error;
> +
> +out_error:
> + trace_xfs_refcount_split_left_extent_error(cur->bc_mp,
> + cur->bc_private.a.agno, error, _RET_IP_);
> + return error;
> +}
> +
> +/*
> + * Split a right rlextent that crosses agbno.
> + */
> +STATIC int
> +try_split_right_rlextent(
> + struct xfs_btree_cur *cur,
> + xfs_agblock_t agbnext)
> +{
> + struct xfs_refcount_irec right, tmp;
> + int found_rec;
> + int error;
> +
> + error = xfs_refcountbt_lookup_le(cur, agbnext - 1, &found_rec);
> + if (error)
> + goto out_error;
> + if (!found_rec)
> + return 0;
> +
> + error = xfs_refcountbt_get_rec(cur, &right, &found_rec);
> + if (error)
> + goto out_error;
> + XFS_WANT_CORRUPTED_GOTO(cur->bc_mp, found_rec == 1, out_error);
> + if (RLNEXT(right) <= agbnext)
> + return 0;
> +
> + trace_xfs_refcount_split_right_extent(cur->bc_mp,
> + cur->bc_private.a.agno, &right, agbnext);
> + tmp = right;
> + tmp.rc_startblock = agbnext;
> + tmp.rc_blockcount -= (agbnext - right.rc_startblock);
> + error = xfs_refcountbt_update(cur, &tmp);
> + if (error)
> + goto out_error;
> +
> + tmp = right;
> + tmp.rc_blockcount = agbnext - right.rc_startblock;
> + error = xfs_refcountbt_insert(cur, &tmp, &found_rec);
> + if (error)
> + goto out_error;
> + XFS_WANT_CORRUPTED_GOTO(cur->bc_mp, found_rec == 1, out_error);
> + return error;
> +
> +out_error:
> + trace_xfs_refcount_split_right_extent_error(cur->bc_mp,
> + cur->bc_private.a.agno, error, _RET_IP_);
> + return error;
> +}
> +
> +/*
> + * Merge the left, center, and right extents.
> + */
> +STATIC int
> +merge_center(
> + struct xfs_btree_cur *cur,
> + struct xfs_refcount_irec *left,
> + struct xfs_refcount_irec *center,
> + unsigned long long extlen,
> + xfs_agblock_t *agbno,
> + xfs_extlen_t *aglen)
> +{
> + int error;
> + int found_rec;
> +
> + error = xfs_refcountbt_lookup_ge(cur, center->rc_startblock,
> + &found_rec);
> + if (error)
> + goto out_error;
> + XFS_WANT_CORRUPTED_GOTO(cur->bc_mp, found_rec == 1, out_error);
> +
> + error = xfs_refcountbt_delete(cur, &found_rec);
> + if (error)
> + goto out_error;
> + XFS_WANT_CORRUPTED_GOTO(cur->bc_mp, found_rec == 1, out_error);
> +
> + if (center->rc_refcount > 1) {
> + error = xfs_refcountbt_delete(cur, &found_rec);
> + if (error)
> + goto out_error;
> + XFS_WANT_CORRUPTED_GOTO(cur->bc_mp, found_rec == 1,
> + out_error);
> + }
> +
> + error = xfs_refcountbt_lookup_le(cur, left->rc_startblock,
> + &found_rec);
> + if (error)
> + goto out_error;
> + XFS_WANT_CORRUPTED_GOTO(cur->bc_mp, found_rec == 1, out_error);
> +
> + left->rc_blockcount = extlen;
> + error = xfs_refcountbt_update(cur, left);
> + if (error)
> + goto out_error;
> +
> + *aglen = 0;
> + return error;
> +
> +out_error:
> + trace_xfs_refcount_merge_center_extents_error(cur->bc_mp,
> + cur->bc_private.a.agno, error, _RET_IP_);
> + return error;
> +}
> +
> +/*
> + * Merge with the left extent.
> + */
> +STATIC int
> +merge_left(
> + struct xfs_btree_cur *cur,
> + struct xfs_refcount_irec *left,
> + struct xfs_refcount_irec *cleft,
> + xfs_agblock_t *agbno,
> + xfs_extlen_t *aglen)
> +{
> + int error;
> + int found_rec;
> +
> + if (cleft->rc_refcount > 1) {
> + error = xfs_refcountbt_lookup_le(cur, cleft->rc_startblock,
> + &found_rec);
> + if (error)
> + goto out_error;
> + XFS_WANT_CORRUPTED_GOTO(cur->bc_mp, found_rec == 1,
> + out_error);
> +
> + error = xfs_refcountbt_delete(cur, &found_rec);
> + if (error)
> + goto out_error;
> + XFS_WANT_CORRUPTED_GOTO(cur->bc_mp, found_rec == 1,
> + out_error);
> + }
> +
> + error = xfs_refcountbt_lookup_le(cur, left->rc_startblock,
> + &found_rec);
> + if (error)
> + goto out_error;
> + XFS_WANT_CORRUPTED_GOTO(cur->bc_mp, found_rec == 1, out_error);
> +
> + left->rc_blockcount += cleft->rc_blockcount;
> + error = xfs_refcountbt_update(cur, left);
> + if (error)
> + goto out_error;
> +
> + *agbno += cleft->rc_blockcount;
> + *aglen -= cleft->rc_blockcount;
> + return error;
> +
> +out_error:
> + trace_xfs_refcount_merge_left_extent_error(cur->bc_mp,
> + cur->bc_private.a.agno, error, _RET_IP_);
> + return error;
> +}
> +
> +/*
> + * Merge with the right extent.
> + */
> +STATIC int
> +merge_right(
> + struct xfs_btree_cur *cur,
> + struct xfs_refcount_irec *right,
> + struct xfs_refcount_irec *cright,
> + xfs_agblock_t *agbno,
> + xfs_extlen_t *aglen)
> +{
> + int error;
> + int found_rec;
> +
> + if (cright->rc_refcount > 1) {
> + error = xfs_refcountbt_lookup_le(cur, cright->rc_startblock,
> + &found_rec);
> + if (error)
> + goto out_error;
> + XFS_WANT_CORRUPTED_GOTO(cur->bc_mp, found_rec == 1,
> + out_error);
> +
> + error = xfs_refcountbt_delete(cur, &found_rec);
> + if (error)
> + goto out_error;
> + XFS_WANT_CORRUPTED_GOTO(cur->bc_mp, found_rec == 1,
> + out_error);
> + }
> +
> + error = xfs_refcountbt_lookup_le(cur, right->rc_startblock,
> + &found_rec);
> + if (error)
> + goto out_error;
> + XFS_WANT_CORRUPTED_GOTO(cur->bc_mp, found_rec == 1, out_error);
> +
> + right->rc_startblock -= cright->rc_blockcount;
> + right->rc_blockcount += cright->rc_blockcount;
> + error = xfs_refcountbt_update(cur, right);
> + if (error)
> + goto out_error;
> +
> + *aglen -= cright->rc_blockcount;
> + return error;
> +
> +out_error:
> + trace_xfs_refcount_merge_right_extent_error(cur->bc_mp,
> + cur->bc_private.a.agno, error, _RET_IP_);
> + return error;
> +}
> +
> +/*
> + * Find the left extent and the one after it (cleft). This function assumes
> + * that we've already split any extent crossing agbno.
> + */
> +STATIC int
> +find_left_extent(
> + struct xfs_btree_cur *cur,
> + struct xfs_refcount_irec *left,
> + struct xfs_refcount_irec *cleft,
> + xfs_agblock_t agbno,
> + xfs_extlen_t aglen)
> +{
> + struct xfs_refcount_irec tmp;
> + int error;
> + int found_rec;
> +
> + left->rc_blockcount = cleft->rc_blockcount = 0;
> + error = xfs_refcountbt_lookup_le(cur, agbno - 1, &found_rec);
> + if (error)
> + goto out_error;
> + if (!found_rec)
> + return 0;
> +
> + error = xfs_refcountbt_get_rec(cur, &tmp, &found_rec);
> + if (error)
> + goto out_error;
> + XFS_WANT_CORRUPTED_GOTO(cur->bc_mp, found_rec == 1, out_error);
> +
> + if (RLNEXT(tmp) != agbno)
> + return 0;
> + /* We have a left extent; retrieve (or invent) the next right one */
> + *left = tmp;
> +
> + error = xfs_btree_increment(cur, 0, &found_rec);
> + if (error)
> + goto out_error;
> + if (found_rec) {
> + error = xfs_refcountbt_get_rec(cur, &tmp, &found_rec);
> + if (error)
> + goto out_error;
> + XFS_WANT_CORRUPTED_GOTO(cur->bc_mp, found_rec == 1,
> + out_error);
> +
> + if (tmp.rc_startblock == agbno)
> + *cleft = tmp;
> + else {
> + cleft->rc_startblock = agbno;
> + cleft->rc_blockcount = min(aglen,
> + tmp.rc_startblock - agbno);
> + cleft->rc_refcount = 1;
> + }
> + } else {
> + cleft->rc_startblock = agbno;
> + cleft->rc_blockcount = aglen;
> + cleft->rc_refcount = 1;
> + }
> + trace_xfs_refcount_find_left_extent(cur->bc_mp, cur->bc_private.a.agno,
> + left, cleft, agbno);
> + return error;
> +
> +out_error:
> + trace_xfs_refcount_find_left_extent_error(cur->bc_mp,
> + cur->bc_private.a.agno, error, _RET_IP_);
> + return error;
> +}
> +
> +/*
> + * Find the right extent and the one before it (cright). This function
> + * assumes that we've already split any extents crossing agbno + aglen.
> + */
> +STATIC int
> +find_right_extent(
> + struct xfs_btree_cur *cur,
> + struct xfs_refcount_irec *right,
> + struct xfs_refcount_irec *cright,
> + xfs_agblock_t agbno,
> + xfs_extlen_t aglen)
> +{
> + struct xfs_refcount_irec tmp;
> + int error;
> + int found_rec;
> +
> + right->rc_blockcount = cright->rc_blockcount = 0;
> + error = xfs_refcountbt_lookup_ge(cur, agbno + aglen, &found_rec);
> + if (error)
> + goto out_error;
> + if (!found_rec)
> + return 0;
> +
> + error = xfs_refcountbt_get_rec(cur, &tmp, &found_rec);
> + if (error)
> + goto out_error;
> + XFS_WANT_CORRUPTED_GOTO(cur->bc_mp, found_rec == 1, out_error);
> +
> + if (tmp.rc_startblock != agbno + aglen)
> + return 0;
> + /* We have a right extent; retrieve (or invent) the next left one */
> + *right = tmp;
> +
> + error = xfs_btree_decrement(cur, 0, &found_rec);
> + if (error)
> + goto out_error;
> + if (found_rec) {
> + error = xfs_refcountbt_get_rec(cur, &tmp, &found_rec);
> + if (error)
> + goto out_error;
> + XFS_WANT_CORRUPTED_GOTO(cur->bc_mp, found_rec == 1,
> + out_error);
> +
> + if (tmp.rc_startblock == agbno)

Since tmp represents the refcount extent immediately to the left of (agbno +
aglen), we want to copy tmp into cright if the end of tmp coincides with (agbno
+ aglen). This is probably a copy-pasta mistake.

Also, s/RLNEXT/RCNEXT/ since these are refcount extents, not reflink extents.
(Weird anachronism).

--D

> + *cright = tmp;
> + else {
> + cright->rc_startblock = max(agbno,
> + RLNEXT(tmp));
> + cright->rc_blockcount = right->rc_startblock -
> + cright->rc_startblock;
> + cright->rc_refcount = 1;
> + }
> + } else {
> + cright->rc_startblock = agbno;
> + cright->rc_blockcount = aglen;
> + cright->rc_refcount = 1;
> + }
> + trace_xfs_refcount_find_right_extent(cur->bc_mp, cur->bc_private.a.agno,
> + cright, right, agbno + aglen);
> + return error;
> +
> +out_error:
> + trace_xfs_refcount_find_right_extent_error(cur->bc_mp,
> + cur->bc_private.a.agno, error, _RET_IP_);
> + return error;
> +}
> +#undef RLNEXT
> +
> +/*
> + * Try to merge with any extents on the boundaries of the adjustment range.
> + */
> +STATIC int
> +try_merge_rlextents(
> + struct xfs_btree_cur *cur,
> + xfs_agblock_t *agbno,
> + xfs_extlen_t *aglen,
> + int adjust)
> +{
> + struct xfs_refcount_irec left, cleft, cright, right;
> + int error;
> + unsigned long long ulen;
> +
> + left.rc_blockcount = cleft.rc_blockcount = 0;
> + cright.rc_blockcount = right.rc_blockcount = 0;
> +
> + /*
> + * Find extents abutting the start and end of the range, and
> + * the adjacent extents inside the range.
> + */
> + error = find_left_extent(cur, &left, &cleft, *agbno, *aglen);
> + if (error)
> + return error;
> + error = find_right_extent(cur, &right, &cright, *agbno, *aglen);
> + if (error)
> + return error;
> +
> + /* No left or right extent to merge; exit. */
> + if (left.rc_blockcount == 0 && right.rc_blockcount == 0)
> + return 0;
> +
> + /* Try a center merge */
> + ulen = (unsigned long long)left.rc_blockcount + cleft.rc_blockcount +
> + right.rc_blockcount;
> + if (left.rc_blockcount != 0 && right.rc_blockcount != 0 &&
> + memcmp(&cleft, &cright, sizeof(cleft)) == 0 &&
> + left.rc_refcount == cleft.rc_refcount + adjust &&
> + right.rc_refcount == cleft.rc_refcount + adjust &&
> + ulen < MAXREFCEXTLEN) {
> + trace_xfs_refcount_merge_center_extents(cur->bc_mp,
> + cur->bc_private.a.agno, &left, &cleft, &right);
> + return merge_center(cur, &left, &cleft, ulen, agbno, aglen);
> + }
> +
> + /* Try a left merge */
> + ulen = (unsigned long long)left.rc_blockcount + cleft.rc_blockcount;
> + if (left.rc_blockcount != 0 &&
> + left.rc_refcount == cleft.rc_refcount + adjust &&
> + ulen < MAXREFCEXTLEN) {
> + trace_xfs_refcount_merge_left_extent(cur->bc_mp,
> + cur->bc_private.a.agno, &left, &cleft);
> + return merge_left(cur, &left, &cleft, agbno, aglen);
> + }
> +
> + /* Try a right merge */
> + ulen = (unsigned long long)right.rc_blockcount + cright.rc_blockcount;
> + if (right.rc_blockcount != 0 &&
> + right.rc_refcount == cright.rc_refcount + adjust &&
> + ulen < MAXREFCEXTLEN) {
> + trace_xfs_refcount_merge_right_extent(cur->bc_mp,
> + cur->bc_private.a.agno, &cright, &right);
> + return merge_right(cur, &right, &cright, agbno, aglen);
> + }
> +
> + return error;
> +}
> +
> +/*
> + * Adjust the refcounts of middle extents. At this point we should have
> + * split extents that crossed the adjustment range; merged with adjacent
> + * extents; and updated agbno/aglen to reflect the merges. Therefore,
> + * all we have to do is update the extents inside [agbno, agbno + aglen].
> + */
> +STATIC int
> +adjust_rlextents(
> + struct xfs_btree_cur *cur,
> + xfs_agblock_t agbno,
> + xfs_extlen_t aglen,
> + int adj,
> + struct xfs_bmap_free *flist,
> + struct xfs_owner_info *oinfo)
> +{
> + struct xfs_refcount_irec ext, tmp;
> + int error;
> + int found_rec, found_tmp;
> + xfs_fsblock_t fsbno;
> +
> + error = xfs_refcountbt_lookup_ge(cur, agbno, &found_rec);
> + if (error)
> + goto out_error;
> +
> + while (aglen > 0) {
> + error = xfs_refcountbt_get_rec(cur, &ext, &found_rec);
> + if (error)
> + goto out_error;
> + if (!found_rec) {
> + ext.rc_startblock = cur->bc_mp->m_sb.sb_agblocks;
> + ext.rc_blockcount = 0;
> + ext.rc_refcount = 0;
> + }
> +
> + /*
> + * Deal with a hole in the refcount tree; if a file maps to
> + * these blocks and there's no refcountbt recourd, pretend that
> + * there is one with refcount == 1.
> + */
> + if (ext.rc_startblock != agbno) {
> + tmp.rc_startblock = agbno;
> + tmp.rc_blockcount = min(aglen,
> + ext.rc_startblock - agbno);
> + tmp.rc_refcount = 1 + adj;
> + trace_xfs_refcount_modify_extent(cur->bc_mp,
> + cur->bc_private.a.agno, &tmp);
> +
> + /*
> + * Either cover the hole (increment) or
> + * delete the range (decrement).
> + */
> + if (tmp.rc_refcount) {
> + error = xfs_refcountbt_insert(cur, &tmp,
> + &found_tmp);
> + if (error)
> + goto out_error;
> + XFS_WANT_CORRUPTED_GOTO(cur->bc_mp,
> + found_tmp == 1, out_error);
> + } else {
> + fsbno = XFS_AGB_TO_FSB(cur->bc_mp,
> + cur->bc_private.a.agno,
> + tmp.rc_startblock);
> + xfs_bmap_add_free(cur->bc_mp, flist, fsbno,
> + tmp.rc_blockcount, oinfo);
> + }
> +
> + agbno += tmp.rc_blockcount;
> + aglen -= tmp.rc_blockcount;
> +
> + error = xfs_refcountbt_lookup_ge(cur, agbno,
> + &found_rec);
> + if (error)
> + goto out_error;
> + }
> +
> + /* Stop if there's nothing left to modify */
> + if (aglen == 0)
> + break;
> +
> + /*
> + * Adjust the reference count and either update the tree
> + * (incr) or free the blocks (decr).
> + */
> + ext.rc_refcount += adj;
> + trace_xfs_refcount_modify_extent(cur->bc_mp,
> + cur->bc_private.a.agno, &ext);
> + if (ext.rc_refcount > 1) {
> + error = xfs_refcountbt_update(cur, &ext);
> + if (error)
> + goto out_error;
> + } else if (ext.rc_refcount == 1) {
> + error = xfs_refcountbt_delete(cur, &found_rec);
> + if (error)
> + goto out_error;
> + XFS_WANT_CORRUPTED_GOTO(cur->bc_mp,
> + found_rec == 1, out_error);
> + goto advloop;
> + } else {
> + fsbno = XFS_AGB_TO_FSB(cur->bc_mp,
> + cur->bc_private.a.agno,
> + ext.rc_startblock);
> + xfs_bmap_add_free(cur->bc_mp, flist, fsbno,
> + ext.rc_blockcount, oinfo);
> + }
> +
> + error = xfs_btree_increment(cur, 0, &found_rec);
> + if (error)
> + goto out_error;
> +
> +advloop:
> + agbno += ext.rc_blockcount;
> + aglen -= ext.rc_blockcount;
> + }
> +
> + return error;
> +out_error:
> + trace_xfs_refcount_modify_extent_error(cur->bc_mp,
> + cur->bc_private.a.agno, error, _RET_IP_);
> + return error;
> +}
> +
> +/*
> + * Adjust the reference count of a range of AG blocks.
> + *
> + * @mp: XFS mount object
> + * @tp: XFS transaction object
> + * @agbp: Buffer containing the AGF
> + * @agno: AG number
> + * @agbno: Start of range to adjust
> + * @aglen: Length of range to adjust
> + * @adj: +1 to increment, -1 to decrement reference count
> + * @flist: freelist (only required if adj == -1)
> + * @owner: owner of the blocks (only required if adj == -1)
> + */
> +STATIC int
> +xfs_refcountbt_adjust_refcount(
> + struct xfs_mount *mp,
> + struct xfs_trans *tp,
> + struct xfs_buf *agbp,
> + xfs_agnumber_t agno,
> + xfs_agblock_t agbno,
> + xfs_extlen_t aglen,
> + int adj,
> + struct xfs_bmap_free *flist,
> + struct xfs_owner_info *oinfo)
> +{
> + struct xfs_btree_cur *cur;
> + int error;
> +
> + cur = xfs_refcountbt_init_cursor(mp, tp, agbp, agno, flist);
> +
> + /*
> + * Ensure that no rlextents cross the boundary of the adjustment range.
> + */
> + error = try_split_left_rlextent(cur, agbno);
> + if (error)
> + goto out_error;
> +
> + error = try_split_right_rlextent(cur, agbno + aglen);
> + if (error)
> + goto out_error;
> +
> + /*
> + * Try to merge with the left or right extents of the range.
> + */
> + error = try_merge_rlextents(cur, &agbno, &aglen, adj);
> + if (error)
> + goto out_error;
> +
> + /* Now that we've taken care of the ends, adjust the middle extents */
> + error = adjust_rlextents(cur, agbno, aglen, adj, flist, oinfo);
> + if (error)
> + goto out_error;
> +
> + xfs_btree_del_cursor(cur, XFS_BTREE_NOERROR);
> + return 0;
> +
> +out_error:
> + trace_xfs_refcount_adjust_error(mp, agno, error, _RET_IP_);
> + xfs_btree_del_cursor(cur, XFS_BTREE_ERROR);
> + return error;
> +}
> +
> +/**
> + * Increase the reference count of a range of AG blocks.
> + *
> + * @mp: XFS mount object
> + * @tp: XFS transaction object
> + * @agbp: Buffer containing the AGF
> + * @agno: AG number
> + * @agbno: Start of range to adjust
> + * @aglen: Length of range to adjust
> + * @flist: List of blocks to free
> + */
> +int
> +xfs_refcount_increase(
> + struct xfs_mount *mp,
> + struct xfs_trans *tp,
> + struct xfs_buf *agbp,
> + xfs_agnumber_t agno,
> + xfs_agblock_t agbno,
> + xfs_extlen_t aglen,
> + struct xfs_bmap_free *flist)
> +{
> + trace_xfs_refcount_increase(mp, agno, agbno, aglen);
> + return xfs_refcountbt_adjust_refcount(mp, tp, agbp, agno, agbno,
> + aglen, 1, flist, NULL);
> +}
> +
> +/**
> + * Decrease the reference count of a range of AG blocks.
> + *
> + * @mp: XFS mount object
> + * @tp: XFS transaction object
> + * @agbp: Buffer containing the AGF
> + * @agno: AG number
> + * @agbno: Start of range to adjust
> + * @aglen: Length of range to adjust
> + * @flist: List of blocks to free
> + * @owner: Extent owner
> + */
> +int
> +xfs_refcount_decrease(
> + struct xfs_mount *mp,
> + struct xfs_trans *tp,
> + struct xfs_buf *agbp,
> + xfs_agnumber_t agno,
> + xfs_agblock_t agbno,
> + xfs_extlen_t aglen,
> + struct xfs_bmap_free *flist,
> + struct xfs_owner_info *oinfo)
> +{
> + trace_xfs_refcount_decrease(mp, agno, agbno, aglen);
> + return xfs_refcountbt_adjust_refcount(mp, tp, agbp, agno, agbno,
> + aglen, -1, flist, oinfo);
> +}
> diff --git a/fs/xfs/libxfs/xfs_refcount.h b/fs/xfs/libxfs/xfs_refcount.h
> index 033a9b1..6640e3d 100644
> --- a/fs/xfs/libxfs/xfs_refcount.h
> +++ b/fs/xfs/libxfs/xfs_refcount.h
> @@ -26,4 +26,12 @@ extern int xfs_refcountbt_lookup_ge(struct xfs_btree_cur *cur,
> extern int xfs_refcountbt_get_rec(struct xfs_btree_cur *cur,
> struct xfs_refcount_irec *irec, int *stat);
>
> +extern int xfs_refcount_increase(struct xfs_mount *mp, struct xfs_trans *tp,
> + struct xfs_buf *agbp, xfs_agnumber_t agno, xfs_agblock_t agbno,
> + xfs_extlen_t aglen, struct xfs_bmap_free *flist);
> +extern int xfs_refcount_decrease(struct xfs_mount *mp, struct xfs_trans *tp,
> + struct xfs_buf *agbp, xfs_agnumber_t agno, xfs_agblock_t agbno,
> + xfs_extlen_t aglen, struct xfs_bmap_free *flist,
> + struct xfs_owner_info *oinfo);
> +
> #endif /* __XFS_REFCOUNT_H__ */
>
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