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: Darrick J. Wong <darrick.wong@oracle.coM>
Reviewed-by: Christoph Hellwig <hch@lst.de>
diff --git a/fs/xfs/libxfs/xfs_refcount.c b/fs/xfs/libxfs/xfs_refcount.c
index 4a31a7c..ab8c30d 100644
--- a/fs/xfs/libxfs/xfs_refcount.c
+++ b/fs/xfs/libxfs/xfs_refcount.c
@@ -1163,3 +1163,105 @@
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;
+}