[elbe-devel] [PATCH v3 1/5] fstab: Find a loop device for losetup

[Olivier Dion]

This fix issue #255, see <https://github.com/Linutronix/elbe/issues/254>.

According to losetup(8), detaching a loop device will not return EBUSY
if the device is busy since kernel 3.7, because of lazy device
destruction.

However, EBUSY is returned if we try to acquire a device that is busy,
even though its reference count is 0.

For this reason, letting losetup to find a proper device and returning
it would avoid such situation.

Signed-off-by: Olivier Dion <dion at linutronix.de>
---
 elbepack/fstab.py | 9 +++++----
 1 file changed, 5 insertions(+), 4 deletions(-)

diff --git a/elbepack/fstab.py b/elbepack/fstab.py
index 94f11d2f..970d508b 100644
--- a/elbepack/fstab.py
+++ b/elbepack/fstab.py
@@ -7,7 +7,7 @@
 
 import os
 
-from elbepack.shellhelper import do
+from elbepack.shellhelper import do, get_command_out
 
 
 def get_mtdnum(xml, label):
@@ -140,9 +140,10 @@ class fstabentry(object):
         self.partnum = ppart.number
         self.number = '{}{}'.format(disk.type, ppart.number)
 
-    def losetup(self, loopdev):
-        do('losetup -o%d --sizelimit %d /dev/%s "%s"' %
-           (self.offset, self.size, loopdev, self.filename))
+    def losetup(self):
+        loopdev = get_command_out('losetup --offset %d --sizelimit %d --find --show "%s"' %
+                                  (self.offset, self.size, self.filename))
+        return loopdev.rstrip('\n')
 
     def tuning(self, loopdev):
         if self.tune:
-- 
2.26.0