From ffa06621c6b2b9a1c186a919154eb8d3ec3d453d Mon Sep 17 00:00:00 2001
From: "emellor@leeni.uk.xensource.com" <emellor@leeni.uk.xensource.com>
Date: Sat, 3 Dec 2005 00:51:36 +0000
Subject: [PATCH] Read from the store if the filename reported by losetup has
 been truncated (the loop driver stores only the first 64 chars of the
 filename).  In this case, we need to read through the store until we find the
 domain using the device, and read the configured filename from there instead.

Signed-off-by: Ewan Mellor <ewan@xensource.com>
---
 tools/examples/block | 37 ++++++++++++++++++++++++++++++++++---
 1 file changed, 34 insertions(+), 3 deletions(-)

diff --git a/tools/examples/block b/tools/examples/block
index e84d1fb415..b37f8fdbd4 100644
--- a/tools/examples/block
+++ b/tools/examples/block
@@ -250,7 +250,7 @@ case "$command" in
       file)
         # Canonicalise the file, for sharing check comparison, and the mode
         # for ease of use here.
-        file=$(readlink -f "$p")
+        file=$(readlink -f "$p") || fatal "$p does not exist."
         mode=$(canonicalise_mode "$mode")
 
         claim_lock "block"
@@ -271,8 +271,7 @@ mount it read-write in a guest domain."
             continue
           fi
 
-          f=$(losetup "$dev" 2>/dev/null) || f='()'
-          f=$(echo "$f" | sed -e 's/.*(\(.*\)).*/\1/g')
+          f=$(losetup "$dev" 2>/dev/null) || f=''
 
           if [ "$f" ]
           then
@@ -282,6 +281,38 @@ mount it read-write in a guest domain."
               continue
             fi
 
+            f=$(echo "$f" | sed -e 's/.*(\(.*\)).*/\1/g')
+
+            # $f is the filename, as read from losetup, but the loopback
+            # driver truncates filenames at 64 characters, so we need to go
+            # trawling through the store if it's longer than that.  Truncation
+            # is indicated by an asterisk at the end of the filename.
+            if expr index "$f" '*' >/dev/null
+            then
+              found=""
+              for dom in $(xenstore-list "$XENBUS_BASE_PATH")
+              do
+                for domdev in $(xenstore-list "$XENBUS_BASE_PATH/$dom")
+                do
+                  d=$(xenstore_read_default \
+                        "$XENBUS_BASE_PATH/$dom/$domdev/node" "")
+                  if [ "$d" == "$dev" ]
+                  then
+                    f=$(xenstore_read "$XENBUS_BASE_PATH/$dom/$domdev/params")
+                    found=1
+                    break 2
+                  fi
+                done
+              done
+
+              if [ ! "$found" ]
+              then
+                # This loopback device is in use by someone else, so skip it.
+                log debug "Loopback sharing check skips device $dev."
+                continue
+              fi
+            fi
+
             f=$(readlink -f "$f")
 
             if [ "$f" == "$file" ]
-- 
2.30.2