[Pvfs2-developers] patches: pvfs2-validate

[Phil Carns]

This is a work in progress, but we wanted to go ahead and share some 
patches to see if anyone has an comments, etc.

The last patch in this email (pvfs2-validate.patch) implements a tool 
similar to pvfs2-fsck that takes a different approach and adds some 
different functionality.  The first two patches are independent changes 
to PVFS2 functionality that make it a little easier to look for file 
system problems.

mgmt-getconfig.patch:
---------------
This patch adds a new PVFS_mgmt_getconfig() function to the management 
interface.  It allows you to retrieve the file system and server 
configuration files verbatim from any arbitrary server in a file system. 
  No protocol changes are necessary because it uses the existing 
getconfig operation.  It also reuses most of the state machine that the 
client normally uses for retrieving configuration data, with some 
modifications that allow it to preserve the text buffers in this case. 
This function is a building block for being able to confirm that the 
server configuration settings are consistent.

sys-getattr-other-objects.patch:
----------------
This patch makes it safe to call PVFS_sys_getattr() directly on 
underlying objects in a file system (such as datafiles), rather than 
juse files, directories, and symlinks.  This is useful for confirming 
valid attributes on individual objects.  Only two changes were needed:
- making sure that only metafiles, dirs, and symlinks get added to the 
acache (attribute cache)
- copying the size out for datafiles

pvfs2-validate.patch:
----------------
This adds a command line tool called pvfs2-validate that is modeled 
after pvfs2-fsck, but diverges in a few ways:

- It uses a new fsck-utils API (PVFS_fsck_XXX()) to do most of the work. 
  This API includes functions for validating various types of PVFS2 
objects and checking for problems.  The PVFS_fsck_XXX() functions just 
make  normal PVFS_sys_XXX() and PVFS_mgmt_XXX() calls under the covers. 
   It includes functions that can walk directory trees as well, so that 
you can just call one top level function to validate an full tree. This 
api could possibly be reused by other admin tools.

- It can be run on individual directory trees or files rather than the 
entire file system.  This is helpful for diagnosing particular suspected 
problem areas on the file system when you don't have time to run a full 
fsck on a large file system.  Running pvfs2-validate on any directory 
other than root disables the check for stranded objects, however, 
because it has to parse the whole tree to make sure that all objects are 
accounted for.

- It can do some basic configuration file sanity checking.  To do this, 
it retrieves the fs.conf from all servers, strips out whitespace and 
comments, and then looks for differences.  If any discrepancies are 
found, it prints a warning and indicates which particular servers appear 
to be using a different fs.conf and what the actual difference is (using 
the first server as the "golden" model).

- It can (optionally) check for bad practice.  These are issues that, 
while not strictly a file system problem, can cause confusion for end 
users.  Examples include special characters (like * or ?) in file names, 
and relative symbolic links that leave the file system (because these 
will break if the mount point is changed).

- As part of its validity checking, it makes sure that all attribute 
values returned for each object are sane, rather than just confirming 
their existance.  For example, does each file have at least one 
datafile, are symlink targets non-null, is size > 0, are the object 
types correct, etc.

- Default output is mostly silent, rather than printing diagnostic 
information for every valid object encountered.

However, there are a few things that pvfs2-validate does _NOT_ do at 
this time:
- it does not make any attempt to repair problems; it only reports them
- it still needs more strenuous testing

Comments and suggestions are welcome...

-Phil
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