svn commit: r248654 - head/sys/sys

[Will Andrews]

Author: will
Date: Sat Mar 23 16:55:07 2013
New Revision: 248654
URL: http://svnweb.freebsd.org/changeset/base/248654

Log:
  Be more explicit about what each bio_cmd & bio_flags value means.
  
  Reviewed by:	ken (mentor)

Modified:
  head/sys/sys/bio.h

Modified: head/sys/sys/bio.h
==============================================================================
--- head/sys/sys/bio.h	Sat Mar 23 16:34:56 2013	(r248653)
+++ head/sys/sys/bio.h	Sat Mar 23 16:55:07 2013	(r248654)
@@ -41,19 +41,23 @@
 #include <sys/queue.h>
 
 /* bio_cmd */
-#define BIO_READ	0x01
-#define BIO_WRITE	0x02
-#define BIO_DELETE	0x04
-#define BIO_GETATTR	0x08
-#define BIO_FLUSH	0x10
+#define BIO_READ	0x01	/* Read I/O data */
+#define BIO_WRITE	0x02	/* Write I/O data */
+#define BIO_DELETE	0x04	/* TRIM or free blocks, i.e. mark as unused */
+#define BIO_GETATTR	0x08	/* Get GEOM attributes of object */
+#define BIO_FLUSH	0x10	/* Commit outstanding I/O now */
 #define BIO_CMD0	0x20	/* Available for local hacks */
 #define BIO_CMD1	0x40	/* Available for local hacks */
 #define BIO_CMD2	0x80	/* Available for local hacks */
 
 /* bio_flags */
-#define BIO_ERROR	0x01
-#define BIO_DONE	0x02
-#define BIO_ONQUEUE	0x04
+#define BIO_ERROR	0x01	/* An error occurred processing this bio. */
+#define BIO_DONE	0x02	/* This bio is finished. */
+#define BIO_ONQUEUE	0x04	/* This bio is in a queue & not yet taken. */
+/*
+ * This bio must be executed after all previous bios in the queue have been
+ * executed, and before any successive bios can be executed.
+ */
 #define BIO_ORDERED	0x08
 #define	BIO_UNMAPPED	0x10
 #define	BIO_TRANSIENT_MAPPING	0x20