From: Bryan Schumaker <bjschuma@xxxxxxxxxx> Signed-off-by: Bryan Schumaker <bjschuma@xxxxxxxxxx> --- Documentation/filesystems/nfs/00-INDEX | 2 + Documentation/filesystems/nfs/fault_injection.txt | 70 +++++++++++++++++++++ 2 files changed, 72 insertions(+), 0 deletions(-) create mode 100644 Documentation/filesystems/nfs/fault_injection.txt diff --git a/Documentation/filesystems/nfs/00-INDEX b/Documentation/filesystems/nfs/00-INDEX index a57e124..1716874 100644 --- a/Documentation/filesystems/nfs/00-INDEX +++ b/Documentation/filesystems/nfs/00-INDEX @@ -2,6 +2,8 @@ - this file (nfs-related documentation). Exporting - explanation of how to make filesystems exportable. +fault_injection.txt + - information for using fault injection on the server knfsd-stats.txt - statistics which the NFS server makes available to user space. nfs.txt diff --git a/Documentation/filesystems/nfs/fault_injection.txt b/Documentation/filesystems/nfs/fault_injection.txt new file mode 100644 index 0000000..b7a4bca --- /dev/null +++ b/Documentation/filesystems/nfs/fault_injection.txt @@ -0,0 +1,70 @@ + +=============== +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 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 forget_locks 1` as root will instruct the server to forget one +lock. Running `inject_faults forget_locks` will instruct the server to forget +all locks. -- 1.7.6.4 -- To unsubscribe from this list: send the line "unsubscribe linux-nfs" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
