+/*
+ * Align startino and allocmask for a recently allocated sparse chunk such that
+ * they are fit for insertion (or merge) into the on-disk inode btrees.
+ *
+ * Background:
+ *
+ * When enabled, sparse inode support increases the inode alignment from cluster
+ * size to inode chunk size. This means that the minimum range between two
+ * non-adjacent inode records in the inobt is large enough for a full inode
+ * record. This allows for cluster sized, cluster aligned block allocation
+ * without need to worry about whether the resulting inode record overlaps with
+ * another record in the tree. Without this basic rule, we would have to deal
+ * with the consequences of overlap by potentially undoing recent allocations in
+ * the inode allocation codepath.
+ *
+ * Because of this alignment rule (which is enforced on mount), there are two
+ * inobt possibilities for newly allocated sparse chunks. One is that the
+ * aligned inode record for the chunk covers a range of inodes not already
+ * covered in the inobt (i.e., it is safe to insert a new sparse record). The
+ * other is that a record already exists at the aligned startino that considers
+ * the newly allocated range as sparse. In the latter case, record content is
+ * merged in hope that sparse inode chunks fill to full chunks over time.
+ */
+STATIC void
+xfs_align_sparse_ino(
+ struct xfs_mount *mp,
+ xfs_agino_t *startino,
+ uint16_t *allocmask)
+{
+ xfs_agblock_t agbno;
+ xfs_agblock_t mod;
+ int offset;
+
+ agbno = XFS_AGINO_TO_AGBNO(mp, *startino);
+ mod = agbno % mp->m_sb.sb_inoalignmt;
+ if (!mod)
+ return;
+
+ /* calculate the inode offset and align startino */
+ offset = mod << mp->m_sb.sb_inopblog;
+ *startino -= offset;
+
+ /*
+ * Since startino has been aligned down, left shift allocmask such that
+ * it continues to represent the same physical inodes relative to the
+ * new startino.
+ */
+ *allocmask <<= offset / XFS_INODES_PER_HOLEMASK_BIT;
+}
+
+/*
+ * Determine whether the source inode record can merge into the target. Both
+ * records must be sparse, the inode ranges must match and there must be no
+ * allocation overlap between the records.
+ */
+STATIC bool
+__xfs_inobt_can_merge(
+ struct xfs_inobt_rec_incore *trec, /* tgt record */
+ struct xfs_inobt_rec_incore *srec) /* src record */
+{
+ uint64_t talloc;
+ uint64_t salloc;
+
+ /* records must cover the same inode range */
+ if (trec->ir_startino != srec->ir_startino)
+ return false;
+
+ /* both records must be sparse */
+ if (!xfs_inobt_issparse(trec->ir_holemask) ||
+ !xfs_inobt_issparse(srec->ir_holemask))
+ return false;
+
+ /* both records must track some inodes */
+ if (!trec->ir_count || !srec->ir_count)
+ return false;
+
+ /* can't exceed capacity of a full record */
+ if (trec->ir_count + srec->ir_count > XFS_INODES_PER_CHUNK)
+ return false;
+
+ /* verify there is no allocation overlap */
+ talloc = xfs_inobt_irec_to_allocmask(trec);
+ salloc = xfs_inobt_irec_to_allocmask(srec);
+ if (talloc & salloc)
+ return false;
+
+ return true;
+}
+
+/*
+ * Merge the source inode record into the target. The caller must call
+ * __xfs_inobt_can_merge() to ensure the merge is valid.
+ */
+STATIC void
+__xfs_inobt_rec_merge(
+ struct xfs_inobt_rec_incore *trec, /* target */
+ struct xfs_inobt_rec_incore *srec) /* src */
+{
+ ASSERT(trec->ir_startino == srec->ir_startino);
+
+ /* combine the counts */
+ trec->ir_count += srec->ir_count;
+ trec->ir_freecount += srec->ir_freecount;
+
+ /*
+ * Merge the holemask and free mask. For both fields, 0 bits refer to
+ * allocated inodes. We combine the allocated ranges with bitwise AND.
+ */
+ trec->ir_holemask &= srec->ir_holemask;
+ trec->ir_free &= srec->ir_free;
+}
+
+/*
+ * Insert a new sparse inode chunk into the associated inode btree. The inode
+ * record for the sparse chunk is pre-aligned to a startino that should match
+ * any pre-existing sparse inode record in the tree. This allows sparse chunks
+ * to fill over time.
+ *
+ * This function supports two modes of handling preexisting records depending on
+ * the merge flag. If merge is true, the provided record is merged with the
+ * existing record and updated in place. The merged record is returned in nrec.
+ * If merge is false, an existing record is replaced with the provided record.
+ * If no preexisting record exists, the provided record is always inserted.
+ *
+ * It is considered corruption if a merge is requested and not possible. Given
+ * the sparse inode alignment constraints, this should never happen.
+ */
+STATIC int
+xfs_inobt_insert_sprec(
+ struct xfs_mount *mp,
+ struct xfs_trans *tp,
+ struct xfs_buf *agbp,
+ int btnum,
+ struct xfs_inobt_rec_incore *nrec, /* in/out: new/merged rec. */
+ bool merge) /* merge or replace */
+{
+ struct xfs_btree_cur *cur;
+ struct xfs_agi *agi = XFS_BUF_TO_AGI(agbp);
+ xfs_agnumber_t agno = be32_to_cpu(agi->agi_seqno);
+ int error;
+ int i;
+ struct xfs_inobt_rec_incore rec;
+
+ cur = xfs_inobt_init_cursor(mp, tp, agbp, agno, btnum);
+
+ /* the new record is pre-aligned so we know where to look */
+ error = xfs_inobt_lookup(cur, nrec->ir_startino, XFS_LOOKUP_EQ, &i);
+ if (error)
+ goto error;
+ /* if nothing there, insert a new record and return */
+ if (i == 0) {
+ error = xfs_inobt_insert_rec(cur, nrec->ir_holemask,
+ nrec->ir_count, nrec->ir_freecount,
+ nrec->ir_free, &i);
+ if (error)
+ goto error;
+ XFS_WANT_CORRUPTED_GOTO(mp, i == 1, error);
+
+ goto out;
+ }
+
+ /*
+ * A record exists at this startino. Merge or replace the record
+ * depending on what we've been asked to do.
+ */
+ if (merge) {
+ error = xfs_inobt_get_rec(cur, &rec, &i);
+ if (error)
+ goto error;
+ XFS_WANT_CORRUPTED_GOTO(mp, i == 1, error);
+ XFS_WANT_CORRUPTED_GOTO(mp,
+ rec.ir_startino == nrec->ir_startino,
+ error);
+
+ /*
+ * This should never fail. If we have coexisting records that
+ * cannot merge, something is seriously wrong.
+ */
+ XFS_WANT_CORRUPTED_GOTO(mp, __xfs_inobt_can_merge(nrec, &rec),
+ error);
+
+ trace_xfs_irec_merge_pre(mp, agno, rec.ir_startino,
+ rec.ir_holemask, nrec->ir_startino,
+ nrec->ir_holemask);
+
+ /* merge to nrec to output the updated record */
+ __xfs_inobt_rec_merge(nrec, &rec);
+
+ trace_xfs_irec_merge_post(mp, agno, nrec->ir_startino,
+ nrec->ir_holemask);
+
+ error = xfs_inobt_rec_check_count(mp, nrec);
+ if (error)
+ goto error;
+ }
+
+ error = xfs_inobt_update(cur, nrec);
+ if (error)
+ goto error;
+
+out:
+ xfs_btree_del_cursor(cur, XFS_BTREE_NOERROR);
+ return 0;
+error:
+ xfs_btree_del_cursor(cur, XFS_BTREE_ERROR);
+ return error;
+}
+