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-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
-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
-Available Faults
- 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.
- 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.
- 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).
- 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.
- 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- been revoked, forcing the client to reaquire the delegation before using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/ 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
-` 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.