+/*
+ * Bump the I/O in flight count on the buftarg if we haven't yet done so for
+ * this buffer. The count is incremented once per buffer (per hold cycle)
+ * because the corresponding decrement is deferred to buffer release. Buffers
+ * can undergo I/O multiple times in a hold-release cycle and per buffer I/O
+ * tracking adds unnecessary overhead. This is used for sychronization purposes
+ * with unmount (see xfs_wait_buftarg()), so all we really need is a count of
+ * in-flight buffers.
+ *
+ * Buffers that are never released (e.g., superblock, iclog buffers) must set
+ * the XBF_NO_IOACCT flag before I/O submission. Otherwise, the buftarg count
+ * never reaches zero and unmount hangs indefinitely.
+ */
+static inline void
+xfs_buf_ioacct_inc(
+ struct xfs_buf *bp)
+{
+ if (bp->b_flags & (XBF_NO_IOACCT|_XBF_IN_FLIGHT))
+ return;
+
+ ASSERT(bp->b_flags & XBF_ASYNC);
+ bp->b_flags |= _XBF_IN_FLIGHT;
+ percpu_counter_inc(&bp->b_target->bt_io_count);
+}
+
+/*
+ * Clear the in-flight state on a buffer about to be released to the LRU or
+ * freed and unaccount from the buftarg.
+ */
+static inline void
+xfs_buf_ioacct_dec(
+ struct xfs_buf *bp)
+{
+ if (!(bp->b_flags & _XBF_IN_FLIGHT))
+ return;
+
+ ASSERT(bp->b_flags & XBF_ASYNC);
+ bp->b_flags &= ~_XBF_IN_FLIGHT;
+ percpu_counter_dec(&bp->b_target->bt_io_count);
+}
+