Merge branch 'for-5.1/nfit/ars' into libnvdimm-for-next

Merge several updates to the ARS implementation. Highlights include:

* Support retrieval of short-ARS results if the ARS state is "requires
  continuation", and even if the "no_init_ars" module parameter is
  specified.
* Allow busy-polling of the kernel ARS state by allowing root to reset
  the exponential back-off timer.
* Filter potentially stale ARS results by tracking query-ARS relative to
  the previous start-ARS.

1 files changed, 17 insertions, 2 deletions

diff --git a/fs/xfs/xfs_buf.c b/fs/xfs/xfs_buf.c
index eedc5e0156ff..4f5f2ff3f70f 100644
--- a/fs/xfs/xfs_buf.c
+++ b/fs/xfs/xfs_buf.c
@@ -776,10 +776,26 @@ _xfs_buf_read(
 }
 
 /*
+ * Set buffer ops on an unchecked buffer and validate it, if possible.
+ *
  * If the caller passed in an ops structure and the buffer doesn't have ops
  * assigned, set the ops and use them to verify the contents.  If the contents
  * cannot be verified, we'll clear XBF_DONE.  We assume the buffer has no
  * recorded errors and is already in XBF_DONE state.
+ *
+ * Under normal operations, every in-core buffer must have buffer ops assigned
+ * to them when the buffer is read in from disk so that we can validate the
+ * metadata.
+ *
+ * However, there are two scenarios where one can encounter in-core buffers
+ * that don't have buffer ops.  The first is during log recovery of buffers on
+ * a V4 filesystem, though these buffers are purged at the end of recovery.
+ *
+ * The other is online repair, which tries to match arbitrary metadata blocks
+ * with btree types in order to find the root.  If online repair doesn't match
+ * the buffer with /any/ btree type, the buffer remains in memory in DONE state
+ * with no ops, and a subsequent read_buf call from elsewhere will not set the
+ * ops.  This function helps us fix this situation.
  */
 int
 xfs_buf_ensure_ops(
@@ -1536,8 +1552,7 @@ __xfs_buf_submit(
 		xfs_buf_ioerror(bp, -EIO);
 		bp->b_flags &= ~XBF_DONE;
 		xfs_buf_stale(bp);
-		if (bp->b_flags & XBF_ASYNC)
-			xfs_buf_ioend(bp);
+		xfs_buf_ioend(bp);
 		return -EIO;
 	}