114a0a08d4
Signed-off-by: Bryan Schumaker <bjschuma@netapp.com> Signed-off-by: J. Bruce Fields <bfields@redhat.com>
69 lines
3 KiB
Text
69 lines
3 KiB
Text
|
|
Fault Injection
|
|
===============
|
|
Fault injection is a method for forcing errors that may not normally occur, or
|
|
may be difficult to reproduce. Forcing these errors in a controlled environment
|
|
can help the developer find and fix bugs before their code is shipped in a
|
|
production system. Injecting an error on the Linux NFS server will allow us to
|
|
observe how the client reacts and if it manages to recover its state correctly.
|
|
|
|
NFSD_FAULT_INJECTION must be selected when configuring the kernel to use this
|
|
feature.
|
|
|
|
|
|
Using Fault Injection
|
|
=====================
|
|
On the client, mount the fault injection server through NFS v4.0+ and do some
|
|
work over NFS (open files, take locks, ...).
|
|
|
|
On the server, mount the debugfs filesystem to <debug_dir> and ls
|
|
<debug_dir>/nfsd. This will show a list of files that will be used for
|
|
injecting faults on the NFS server. As root, write a number n to the file
|
|
corresponding to the action you want the server to take. The server will then
|
|
process the first n items it finds. So if you want to forget 5 locks, echo '5'
|
|
to <debug_dir>/nfsd/forget_locks. A value of 0 will tell the server to forget
|
|
all corresponding items. A log message will be created containing the number
|
|
of items forgotten (check dmesg).
|
|
|
|
Go back to work on the client and check if the client recovered from the error
|
|
correctly.
|
|
|
|
|
|
Available Faults
|
|
================
|
|
forget_clients:
|
|
The NFS server keeps a list of clients that have placed a mount call. If
|
|
this list is cleared, the server will have no knowledge of who the client
|
|
is, forcing the client to reauthenticate with the server.
|
|
|
|
forget_openowners:
|
|
The NFS server keeps a list of what files are currently opened and who
|
|
they were opened by. Clearing this list will force the client to reopen
|
|
its files.
|
|
|
|
forget_locks:
|
|
The NFS server keeps a list of what files are currently locked in the VFS.
|
|
Clearing this list will force the client to reclaim its locks (files are
|
|
unlocked through the VFS as they are cleared from this list).
|
|
|
|
forget_delegations:
|
|
A delegation is used to assure the client that a file, or part of a file,
|
|
has not changed since the delegation was awarded. Clearing this list will
|
|
force the client to reaquire its delegation before accessing the file
|
|
again.
|
|
|
|
recall_delegations:
|
|
Delegations can be recalled by the server when another client attempts to
|
|
access a file. This test will notify the client that its delegation has
|
|
been revoked, forcing the client to reaquire the delegation before using
|
|
the file again.
|
|
|
|
|
|
tools/nfs/inject_faults.sh script
|
|
=================================
|
|
This script has been created to ease the fault injection process. This script
|
|
will detect the mounted debugfs directory and write to the files located there
|
|
based on the arguments passed by the user. For example, running
|
|
`inject_faults.sh forget_locks 1` as root will instruct the server to forget
|
|
one lock. Running `inject_faults forget_locks` will instruct the server to
|
|
forgetall locks.
|