# HG changeset patch
# User emellor@xxxxxxxxxxxxxxxxxxxxxx
# Node ID 8a00d9af329136d93937e10f5d207e4cb1a77364
# Parent 74fa88cf3dc7cc3132b8532ac65a5d1d6de2b63f
Tidy and comment use of canonicalise_mode, et al.
Signed-off-by: Ewan Mellor <ewan@xxxxxxxxxxxxx>
diff -r 74fa88cf3dc7 -r 8a00d9af3291 tools/examples/block
--- a/tools/examples/block Tue Nov 29 15:00:27 2005
+++ b/tools/examples/block Tue Nov 29 15:01:47 2005
@@ -1,6 +1,4 @@
#!/bin/sh
-
-set -x
dir=$(dirname "$0")
. "$dir/block-common.sh"
@@ -19,30 +17,49 @@
}
+##
+# canonicalise_mode mode
+#
+# Takes the given mode, which may be r, w, ro, rw, w!, or rw!, or variations
+# thereof, and canonicalises them to one of
+#
+# 'r': perform checks for a new read-only mount;
+# 'w': perform checks for a read-write mount; or
+# '!': perform no checks at all.
+#
canonicalise_mode()
{
local mode="$1"
if ! expr index "$mode" 'w' >/dev/null
then
- echo 'ro'
+ echo 'r'
elif ! expr index "$mode" '!' >/dev/null
then
- echo 'rw'
+ echo 'w'
else
- echo 'no'
- fi
-}
-
-
-##
-# check_sharing device device_major_minor mode
+ echo '!'
+ fi
+}
+
+
+##
+# check_sharing device mode
#
# Check whether the device requested is already in use. To use the device in
# read-only mode, it may be in use in read-only mode, but may not be in use in
# read-write anywhere at all. To use the device in read-write mode, it must
# not be in use anywhere at all.
#
+# Prints one of
+#
+# 'local': the device may not be used because it is mounted in the current
+# (i.e. the privileged domain) in a way incompatible with the
+# requested mode;
+# 'guest': the device may not be used because it already mounted by a guest
+# in a way incompatible with the requested mode; or
+# 'ok': the device may be used.
+#
check_sharing()
{
local dev="$1"
@@ -51,7 +68,7 @@
local devmm=$(device_major_minor "$dev")
local file
- if [ "$mode" == 'rw' ]
+ if [ "$mode" == 'w' ]
then
toskip="^$"
else
@@ -79,7 +96,7 @@
local d=$(cat "$file")
if [ "$d" == "$devmm" ]
then
- if [ "$mode" == 'rw' ]
+ if [ "$mode" == 'w' ]
then
echo 'guest'
return
@@ -100,13 +117,18 @@
}
+##
+# check_device_sharing dev mode
+#
+# Perform the sharing check for the given physical device and mode.
+#
check_device_sharing()
{
local dev="$1"
local mode=$(canonicalise_mode "$2")
local result
- if [ "$mode" == 'no' ]
+ if [ "$mode" == '!' ]
then
return 0
fi
@@ -120,6 +142,12 @@
}
+##
+# check_device_sharing file dev mode
+#
+# Perform the sharing check for the given file mounted through the given
+# loopback interface, in the given mode.
+#
check_file_sharing()
{
local file="$1"
@@ -136,6 +164,13 @@
}
+##
+# do_ebusy prefix mode result
+#
+# Helper function for check_device_sharing check_file_sharing, calling ebusy
+# with an error message constructed from the given prefix, mode, and result
+# from a call to check_sharing.
+#
do_ebusy()
{
local prefix="$1"
@@ -151,7 +186,7 @@
when='by a guest'
fi
- if [ "$mode" == 'rw' ]
+ if [ "$mode" == 'w' ]
then
m1=''
m2=''
@@ -195,7 +230,7 @@
file=$(readlink -f "$p")
mode=$(canonicalise_mode "$mode")
- if [ "$mode" == 'rw' ] && ! stat "$file" -c %A | grep w >&/dev/null
+ if [ "$mode" == 'w' ] && ! stat "$file" -c %A | grep -q w
then
ebusy \
"File $file is read-only, and so I will not
@@ -221,7 +256,7 @@
if [ "$f" ]
then
# $dev is in use. Check sharing.
- if [ "$mode" == 'no' ]
+ if [ "$mode" == '!' ]
then
continue
fi
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