xfs: move the buffer retry logic to xfs_buf.c

Source kernel commit: 664ffb8a429a800c51964b94c15c6a92c8d8334c

Move the buffer retry state machine logic to xfs_buf.c and call it once
from xfs_ioend instead of duplicating it three times for the three kinds
of buffers.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Darrick J. Wong <darrick.wong@oracle.com>
Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
diff --git a/libxfs/xfs_trans_inode.c b/libxfs/xfs_trans_inode.c
index 82716ea..a392fd2 100644
--- a/libxfs/xfs_trans_inode.c
+++ b/libxfs/xfs_trans_inode.c
@@ -174,9 +174,9 @@
 
 	/*
 	 * Always OR in the bits from the ili_last_fields field.  This is to
-	 * coordinate with the xfs_iflush() and xfs_iflush_done() routines in
-	 * the eventual clearing of the ili_fields bits.  See the big comment in
-	 * xfs_iflush() for an explanation of this coordination mechanism.
+	 * coordinate with the xfs_iflush() and xfs_buf_inode_iodone() routines
+	 * in the eventual clearing of the ili_fields bits.  See the big comment
+	 * in xfs_iflush() for an explanation of this coordination mechanism.
 	 */
 	iip->ili_fields |= (flags | iip->ili_last_fields | iversion_flags);
 	spin_unlock(&iip->ili_lock);