Module Name: src
Committed By: haad
Date: Wed Dec 30 00:08:01 UTC 2009
Modified Files:
src/share/man/man9: disk.9
Log Message:
Mention problems which disk api have with concurrent usage remove splbio
line from man page because it is not true anymore, mention disk_isbusy and
add dm driver to references.
To generate a diff of this commit:
cvs rdiff -u -r1.32 -r1.33 src/share/man/man9/disk.9
Please note that diffs are not public domain; they are subject to the
copyright notices on the relevant files.
Modified files:
Index: src/share/man/man9/disk.9
diff -u src/share/man/man9/disk.9:1.32 src/share/man/man9/disk.9:1.33
--- src/share/man/man9/disk.9:1.32 Wed May 20 06:38:39 2009
+++ src/share/man/man9/disk.9 Wed Dec 30 00:08:01 2009
@@ -1,4 +1,4 @@
-.\" $NetBSD: disk.9,v 1.32 2009/05/20 06:38:39 wiz Exp $
+.\" $NetBSD: disk.9,v 1.33 2009/12/30 00:08:01 haad Exp $
.\"
.\" Copyright (c) 1995, 1996 Jason R. Thorpe.
.\" All rights reserved.
@@ -30,7 +30,7 @@
.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
.\" SUCH DAMAGE.
.\"
-.Dd May 19, 2009
+.Dd December 30, 2009
.Dt DISK 9
.Os
.Sh NAME
@@ -42,6 +42,7 @@
.Nm disk_destroy ,
.Nm disk_busy ,
.Nm disk_unbusy ,
+.Nm disk_isbusy ,
.Nm disk_find ,
.Nm disk_blocksize
.Nd generic disk framework
@@ -63,6 +64,8 @@
.Fn disk_busy "struct disk *"
.Ft void
.Fn disk_unbusy "struct disk *" "long bcount" "int read"
+.Ft bool
+.Fn disk_isbusy "struct disk *"
.Ft struct disk *
.Fn disk_find "const char *"
.Ft void
@@ -127,8 +130,10 @@
Drivers which currently make use of the detachment
capability of the framework are the
.Nm ccd
-and
+,
.Nm vnd
+and
+.Nm dm
pseudo-device drivers.
.Pp
The following is a brief description of each function in the framework:
@@ -181,6 +186,10 @@
specifies the direction of I/O;
if non-zero it means reading from the disk,
otherwise it means writing to the disk.
+.It Fn disk_isbusy
+Returns
+.Ar true
+if disk is marked as busy and false if it is not.
.It Fn disk_find
Return a pointer to the disk structure corresponding to the name provided,
or NULL if the disk does not exist.
@@ -374,6 +383,14 @@
and
.Fn disk_unbusy
routines.
+Because
+.Nm struct disk
+is part of device driver private data it needs to be guarded. Mutual exclusion
+must be done by driver
+.Fn disk_busy
+and
+.Fn disk_unbusy
+are not thread safe.
The
.Fn disk_busy
routine should be called immediately before a command to the disk is
@@ -392,7 +409,9 @@
[ . . . ]
/* Tell the disk framework we're going busy. */
+ mutex_enter(\*[Am]sc-\*[Gt]sc_dk_mtx);
disk_busy(\*[Am]sc-\*[Gt]sc_dk);
+ mutex_exit(\*[Am]sc-\*[Gt]sc_dk_mtx);
/* Send command to the drive. */
[ . . . ]
@@ -403,10 +422,6 @@
.Fn disk_busy
is called, a timestamp is taken if the disk's busy counter moves from
0 to 1, indicating the disk has gone from an idle to non-idle state.
-Note that
-.Fn disk_busy
-must be called at
-.Fn splbio .
At the end of a transaction, the
.Fn disk_unbusy
routine should be called.
@@ -451,19 +466,23 @@
[ . . . ]
+ mutex_enter(\*[Am]sc-\*[Gt]sc_dk_mtx);
/* Notify the disk framework that we've completed the transfer. */
disk_unbusy(\*[Am]sc-\*[Gt]sc_dk, nbytes,
bp != NULL ? bp-\*[Gt]b_flags \*[Am] B_READ : 0);
+ mutex_exit(\*[Am]sc-\*[Gt]sc_dk_mtx);
[ . . . ]
}
.Ed
.Pp
-Like
-.Fn disk_busy ,
+.Fn disk_isbusy
+is used to get status of disk device it returns true if device is currently busy
+and false if it is not. Like
+.Fn disk_busy
+and
.Fn disk_unbusy
-must be called at
-.Fn splbio .
+it requires explicit locking from user side.
.Sh CODE REFERENCES
This section describes places within the
.Nx
@@ -489,17 +508,21 @@
The
.Nx
.Nm ccd
-and
+,
.Nm vnd
+and
+.Nm dm
drivers use the detachment capability of the framework.
They are located in
.Pa sys/dev/ccd.c
+,
+.Pa sys/dev/vnd.c
and
-.Pa sys/dev/vnd.c .
+.Pa sys/dev/dm/device-mapper.c .
.Sh SEE ALSO
.Xr ccd 4 ,
.Xr vnd 4 ,
-.Xr spl 9
+.Xr dm 4
.Sh HISTORY
The
.Nx
