Re: [PATCH 00/10] Kernel patch series

[Jim Carter <jimc@math.ucla.edu>]

On Thu, 12 Jun 2008, Ian Kent wrote:

> Here are the kernel patches I recommend we use while testing
> the submount hang problem.
> 
> Some are upstream in recent kernels while others address known
> problems. They were amde against a 2.6.24 source base but should
> apply to earlier kernels. They may not be in thier final state
> as testing is still being done.
> --snip--
> Ian Kent (8):
>       autofs4 - fix pending mount race.
>       autofs4 - use lookup intent flags to trigger mounts
>       autofs4 - don't release directory mutex if called in oz_mode
>       autofs4 - use look aside list for lookups
>       autofs4 - don't make expiring dentry negative
>       autofs4 - fix mntput, dput order bug
>       autofs4 - fix sparse warning in waitq.c:autofs4_expire_indirect()
>       autofs4 - check for invalid dentry in getpath
> 
> Jeff Moyer (2):
>       autofs4 - use struct qstr in waitq.c
>       autofs4 - fix incorrect return from root.c:try_to_fill_dentry()

Unfortunately some of the patches didn't go on cleanly.  I'm using kernel 
2.6.22.17, specifically SuSE's kernel-source-2.6.22.17-0.1 updated package 
and the "default" kernel.  Applying to a pristine copy of the source I had 
these failures:

autofs4-dont-make-expiring-dentry-negative  
    #I had to do this one by hand, but I'm pretty sure I got the right
    #locations and there were no screwups.
autofs4-use-look-aside-list-for-lookups 
    #Hunk 8 at 763: in root.c in autofs4_dir_symlink 
    #after inode = autofs4_get_inode(dir->i_sb, ino); at 698 and ENOMEM 
    #test my source (outside the patch) has d_instantiate(dentry, inode); 
    #yours has d_add(dentry, inode);  I did not make this change.
    #Hunk 12 at 914 in autofs4_dir_mkdir
    #Identical code; I left this one alone also.

In addition, there was a compilation error, an instance of "unhashed", 
which I changed to "expiring".  This was in root.c in autofs4_lookup at
552, in the if(expiring) block, it said dentry = unhashed (which is 
undefined) and I changed it to dentry = expiring.  

Surely one of these hacks was a misjudgment.  After I stopped the daemon, 
removed the module, installed the new module, and restarted the daemon,
on the first attempt to automount something (all my automounts involve 
submounts), it complained in syslog:

Jun 13 17:40:14 serval automount[11652]: do_mount_autofs_indirect: failed 
    to mount autofs path /net/julia
Jun 13 17:40:14 serval automount[11652]: rmdir_path: lstat of /net/julia 
    failed
Jun 13 17:40:14 serval automount[11652]: handle_mounts: mount of /net/julia 
    failed!
Jun 13 17:40:14 serval automount[11652]: mount_mount: mount(autofs): failed 
    to create submount for /net/julia

(This was repeated every few seconds, likely because my shell was statting 
this dir repeatedly.)  When I stopped the daemon I got a kernel panic.

Likely there's no point debugging this -- blame it on version skew.  And of 
course it's going to take some digging to find out for sure just which 
patches have been applied to these kernel sources.  How do you suggest we 
proceed?  

Aw, crap, I removed the patched module, did depmod -a (the original module 
is still there), and rebooted the test machine.  It doesn't seem to want to 
come up, and I'm working from home...  

James F. Carter          Voice 310 825 2897    FAX 310 206 6673
UCLA-Mathnet;  6115 MSA; 520 Portola Plaza; Los Angeles, CA, USA  90095-1555
Email: jimc@math.ucla.edu    http://www.math.ucla.edu/~jimc (q.v. for PGP key)