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authorLinus Torvalds <torvalds@linux-foundation.org>2012-01-14 12:26:41 -0800
committerLinus Torvalds <torvalds@linux-foundation.org>2012-01-14 12:26:41 -0800
commit0b48d42235caf627121f440b57d376f48a9af8b6 (patch)
tree400967c5fcb1cd08bbc0e1739e229f9717590f19 /Documentation/filesystems/nfs/fault_injection.txt
parent8e63dd6e1c589ba99a18df9cbaa41c3178607641 (diff)
parent7a6ef8c72314f254c107c6a9ed7cb201961ee05a (diff)
Merge branch 'for-3.3' of git://linux-nfs.org/~bfields/linux
* 'for-3.3' of git://linux-nfs.org/~bfields/linux: (31 commits) nfsd4: nfsd4_create_clid_dir return value is unused NFSD: Change name of extended attribute containing junction svcrpc: don't revert to SVC_POOL_DEFAULT on nfsd shutdown svcrpc: fix double-free on shutdown of nfsd after changing pool mode nfsd4: be forgiving in the absence of the recovery directory nfsd4: fix spurious 4.1 post-reboot failures NFSD: forget_delegations should use list_for_each_entry_safe NFSD: Only reinitilize the recall_lru list under the recall lock nfsd4: initialize special stateid's at compile time NFSd: use network-namespace-aware cache registering routines SUNRPC: create svc_xprt in proper network namespace svcrpc: update outdated BKL comment nfsd41: allow non-reclaim open-by-fh's in 4.1 svcrpc: avoid memory-corruption on pool shutdown svcrpc: destroy server sockets all at once svcrpc: make svc_delete_xprt static nfsd: Fix oops when parsing a 0 length export nfsd4: Use kmemdup rather than duplicating its implementation nfsd4: add a separate (lockowner, inode) lookup nfsd4: fix CONFIG_NFSD_FAULT_INJECTION compile error ...
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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
+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.