Bug 165245 - KDE does not start on CIFS-mounted home directories (lockfile problem)
Summary: KDE does not start on CIFS-mounted home directories (lockfile problem)
Status: RESOLVED DUPLICATE of bug 156759
Alias: None
Product: kdelibs
Classification: Unmaintained
Component: general (show other bugs)
Version: unspecified
Platform: openSUSE Linux
: NOR normal
Target Milestone: ---
Assignee: kdelibs bugs
URL:
Keywords:
Depends on:
Blocks:
 
Reported: 2008-06-28 23:26 UTC by bjoernv
Modified: 2008-09-19 21:46 UTC (History)
1 user (show)

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Description bjoernv 2008-06-28 23:26:25 UTC
Version:           1.0.2 (using KDE 4.0.5)
Installed from:    SuSE RPMs
Compiler:          gcc 4.2.1 
OS:                Linux

KDE does not start, if the home directory is a CIFS mount. I use samba-3.0.26a-3.7 (Server) and cifs-mount-3.0.26a-3.7 (Client) on Linux (openSUSE 10.3). cifs-mount should provide enough UNIX compatibility to run any Unix application (including symlinks, hard links etc.).

There are problems with lockfiles for kconf_update in the X session logs:

WARNING: Problem deleting stale lockfile /home/bv/.kde4/share/config/kconf_updaterc.lock
WARNING: Problem deleting stale lockfile /home/bv/.kde4/share/config/kconf_updaterc.lock
WARNING: Problem deleting stale lockfile /home/bv/.kde4/share/config/kconf_updaterc.lock
[...]
(endless loop)

The problem already exists on KDE 3.x. But I also find the problem on KDE 4.0.5. The source code already contains some work arounds for the file locking problem for SMBFS (a predecessor of CIFS) shares:

http://lxr.kde.org/source/KDE/kdelibs/kdecore/io/klockfile_unix.cpp:
225    // SMBFS supports hardlinks by copying the file, as a result the above test will always fail
226    if (linkCountSupport)
227    {
228       linkCountSupport = testLinkCountSupport(tmpFile);
229    }
230 
231    if (!linkCountSupport &&
232        (KDE_lstat(lckFile, &st_buf2) == 0) && st_buf == st_buf2)
233    {
234       // Without support for link counts we will have a little race condition
235       qWarning("WARNING: deleting stale lockfile %s", lckFile.data());
236       ::unlink(lckFile);
237       ::unlink(tmpFile);
238       return KLockFile::LockOK;
239    }
240 
241    // Failed to delete stale lock file
242    qWarning("WARNING: Problem deleting stale lockfile %s", lckFile.data());
243    ::unlink(tmpFile);
244    return KLockFile::LockFail;

linkCountSupport is false on in my setup. But the second check (KDE_lstat(lckFile, &st_buf2) == 0) && st_buf == st_buf2 is also false because the st_link fields are not equal. As the result, the error message "WARNING: Problem deleting stale lockfile %s" is displayed.

Without a fix for this problem the KDE start script runs in an infinite loop, because kconf_update does not terminate. Probably also single KDE applications may fail on CIFS, because some of them use the KLockFile class, which is broken for CIFS.
Comment 1 bjoernv 2008-06-29 13:03:00 UTC
Here are some additional notes for linux-cifs support. My testing is still based on samba-3.0.26a-3.7 (Server) and cifs-mount-3.0.26a-3.7 (Client) on Linux (openSUSE 10.3). Other setups (for instance Windows server) may produce other results.

- hard links could be created on the remote CIFS site
  # ln file1 link1

- on the server site the newly created links are really hard links
  # ls -li file1 link1
  48843 -rw-r--r-- 2 bv bv 0 29. Jun 12:34 file1
  48843 -rw-r--r-- 2 bv bv 0 29. Jun 12:34 link1

- on the server site "file1" and "link1" both have the same link count, 
  but not the same inode number. 
  # ls -li file1 link1
  43502 -rw-r--r-- 2 bv bv 0 29. Jun 12:34 file1
  43503 -rw-r--r-- 2 bv bv 0 29. Jun 12:34 link1

- The inode numbers are not based on the server inode numbers. Other each 
  new mount the inode numbers may change on the client site:
  # cd /
  # sudo umount /home
  # sudo mount -t cifs //chemnitz/bv /home/bv -o username=bv
  Password:
  # cd
  # ls -li file1 link1
  47570 -rw-r--r-- 2 bv bv 0 29. Jun 12:34 file1
  47575 -rw-r--r-- 2 bv bv 0 29. Jun 12:34 link1

This behavior results in the fact that 

231    if (!linkCountSupport &&
232        (KDE_lstat(lckFile, &st_buf2) == 0) && st_buf == st_buf2)

is false on CIFS, because st_buf is not st_buf2 (the inode numbers do not match). 
Comment 2 David Faure 2008-09-19 21:46:02 UTC
I wish I had seen this investigation before spending time on 156759...

*** This bug has been marked as a duplicate of bug 156759 ***