[PATCH v2 08/17] xfs: create helper to manage record overlap for sparse inode chunks

[Brian Foster <bfoster@redhat.com>]

Create xfs_inobt_rec_exists() to receive the parameters of a new sparse
inode chunk allocation and identify whether a record exists that is
capable of tracking this sparse chunk.

Signed-off-by: Brian Foster <bfoster@redhat.com>
---
 fs/xfs/libxfs/xfs_ialloc.c | 61 ++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 61 insertions(+)

diff --git a/fs/xfs/libxfs/xfs_ialloc.c b/fs/xfs/libxfs/xfs_ialloc.c
index b53fb5d..6879213 100644
--- a/fs/xfs/libxfs/xfs_ialloc.c
+++ b/fs/xfs/libxfs/xfs_ialloc.c
@@ -359,6 +359,67 @@ xfs_ialloc_inode_init(
 }
 
 /*
+ * Determine whether part of a sparse inode chunk that has just been allocated
+ * is covered by an existing inobt record.
+ */
+STATIC int
+xfs_inobt_rec_exists(
+	struct xfs_mount		*mp,
+	struct xfs_trans		*tp,
+	struct xfs_buf			*agbp,
+	xfs_agino_t			newino,
+	xfs_agino_t			count,
+	xfs_btnum_t			btnum,
+	struct xfs_inobt_rec_incore	*orec)
+{
+	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;
+
+	orec->ir_startino = NULLAGINO;
+
+	cur = xfs_inobt_init_cursor(mp, tp, agbp, agno, btnum);
+
+	/*
+	 * Find the first record prior to the inode that has just been
+	 * allocated.
+	 */
+	error = xfs_inobt_lookup(cur, newino, XFS_LOOKUP_LE, &i);
+	if (error)
+		goto error;
+	if (i == 0)
+		goto out;
+
+	error = xfs_inobt_get_rec(cur, &rec, &i);
+	if (error)
+		goto error;
+	XFS_WANT_CORRUPTED_GOTO(i == 1, error);
+
+	/*
+	 * Check whether the record covers a range that includes the new inodes.
+	 * We can't allocate a sparse chunk that spans multiple records, so we
+	 * only need to check the ino range.
+	 */
+	if (rec.ir_startino + XFS_INODES_PER_CHUNK <= newino)
+		goto out;
+
+	ASSERT(rec.ir_startino <= newino &&
+	       rec.ir_startino + XFS_INODES_PER_CHUNK > newino);
+
+	*orec = rec;	/* struct copy */
+
+out:
+	xfs_btree_del_cursor(cur, XFS_BTREE_NOERROR);
+	return 0;
+error:
+	xfs_btree_del_cursor(cur, XFS_BTREE_ERROR);
+	return error;
+}
+
+/*
  * Allocate new inodes in the allocation group specified by agbp.
  * Return 0 for success, else error code.
  */
-- 
1.8.3.1

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