Document the implementation of error handlers into sysfs. Changelog: V2: - Add a description of the precedence order of each option, focusing on the behavior of "fail_at_unmount" which was not well explained in V1 V3: - Fix English spelling mistakes suggested by Eric Signed-off-by: Carlos Maiolino <cmaiolino@xxxxxxxxxx> --- Documentation/filesystems/xfs.txt | 70 +++++++++++++++++++++++++++++++++++++++ 1 file changed, 70 insertions(+) diff --git a/Documentation/filesystems/xfs.txt b/Documentation/filesystems/xfs.txt index 8146e9f..8b6c861 100644 --- a/Documentation/filesystems/xfs.txt +++ b/Documentation/filesystems/xfs.txt @@ -348,3 +348,73 @@ Removed Sysctls ---- ------- fs.xfs.xfsbufd_centisec v4.0 fs.xfs.age_buffer_centisecs v4.0 + +Error handling +============== + +XFS can act differently according to the type of error found +during its operation. The implementation introduces the following +concepts to the error handler: + + -failure speed: + Defines how fast XFS should shut down when of a specific error is found + during the filesystem operation. It can shut down immediately, after a + defined number of retries, after a set time period, or simply retry + forever. The old "retry forever" behavior is still the default, except + during unmount, where any IOs retrying due to errors will be cancelled + and unmount will be allowed to proceed. + + -error classes: + Specifies the subsystem/location where the error handlers, such as + metadata or memory allocation. Only metadata IO errors are handled + at this time. + + -error handlers: + Defines the behavior for a specific error. + +The filesystem behavior during an error can be set via sysfs files, where the +errors are organized with the structure below. Each configuration option works +independently, the first condition met for a specific configuration will cause +the filesystem to shut down: + + /sys/fs/xfs/<dev>/error/<class>/<error>/ + +Each directory contains: + + /sys/fs/xfs/<dev>/error/ + + fail_at_unmount (Min: 0 Default: 1 Max: 1) + Defines the global error behavior at unmount time. If set to the + default value of 1, XFS will cancel any pending IO retries, shut + down, and unmount. If set to 0, pending IO retries may prevent + the filesystem from unmounting. + + <class> subdirectories + Contains specific error handlers configuration + (Ex: /sys/fs/xfs/<dev>/error/metadata, see below). + + /sys/fs/xfs/<dev>/error/<class>/ + + Directory containing configuration for a specific error <class>; + currently only the "metadata" <class> is implemented. + The contents of this directory are <class> specific, since each <class> + might need to handle different types of errors. + + /sys/fs/xfs/<dev>/error/<class>/<error>/ + + Contains the failure speed configuration files for specific errors in + this <class, as well as a "default" behavior. Each <error> directory + contains the following configuration files: + + max_retries (Min: -1 Default: -1 Max: INTMAX) + Defines the allowed number of retries of a specific error before + the filesystem will shut down. The default value of "-1" will + cause XFS to retry forever for this specific error. Setting it + to "0" will cause XFS to fail immediately when the specific + error is found, and setting it to "N," where N is greater than 0, + will make XFS retry "N" times before shutting down. + + retry_timeout_seconds (Min: 0 Default: 0 Max: INTMAX) + Define the amount of time (in seconds) that the filesystem is + allowed to retry its operations when the specific error is + found. The default value of "0" will cause XFS to retry forever. -- 2.5.5 -- To unsubscribe from this list: send the line "unsubscribe linux-xfs" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
