On Tue, Jul 19, 2016 at 12:04:17PM +0200, Carlos Maiolino wrote:
> This is the first try to document the implementation of error handlers into
> sysfs.
>
> Reviews and comments are appreciated, please also notice I'm not
> english-native,
> so, spelling corrections are also appreciated :)
>
> Signed-off-by: Carlos Maiolino <cmaiolino@xxxxxxxxxx>
> ---
> Documentation/filesystems/xfs.txt | 78
> +++++++++++++++++++++++++++++++++++++++
> 1 file changed, 78 insertions(+)
>
> diff --git a/Documentation/filesystems/xfs.txt
> b/Documentation/filesystems/xfs.txt
> index 8146e9f..1df868a 100644
> --- a/Documentation/filesystems/xfs.txt
> +++ b/Documentation/filesystems/xfs.txt
> @@ -348,3 +348,81 @@ Removed Sysctls
> ---- -------
> fs.xfs.xfsbufd_centisec v4.0
> fs.xfs.age_buffer_centisecs v4.0
> +
> +Error handling
> +==============
> +
> +XFS can act differently according with 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 shutdown in case of a specific
> + error is found during the filesystem operation. It can
> + shutdown immediately, after a defined number of tries, or
> + simply try forever, which was the old behavior and is now
> + set as default behavior, except during unmount time, where
> + in case of a error is found while unmounting, the filesystem
> + will shutdown.
> +
> + -error classes:
> + Specifies the subsystem/location where the error handlers
> + configure the behavior for, such as metadata or memory allocation.
> +
> + -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 following structure:
> +
> + /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 during unmount time. If set to
> + "1", XFS will shutdown in case of any error is found, otherwise,
> + if set to "0", the filesystem will indefinitely retry to cleanly
> + unmount the filesystem.
Hi Carlos,
Could you explain more about the relationship of fail_at_unmount and
max_retries(/retry_timeout_seconds). For example, if I set fail_at_unmount=0,
and set EIO/max_retries=1, what's expected?
I'd like to write test case about this error handling, according to
your document.
Thanks,
Zorro
> +
> + <class> subdirectories
> + Contains specific error handlers configuration
> + (Ex: /sys/fs/xfs/<dev>/error/metadata).
> +
> + /sys/fs/xfs/<dev>/error/<class>/
> +
> + The contents of this directory are <class> specific, since each <class>
> + might need to handle different types of errors. All <error> directory
> + though, contains the "default" directory, which is a global
> configuration
> + for errors not available for independent configuration.
> +
> + /sys/fs/xfs/<dev>/error/<class>/<error>
> +
> + Contains the failure speed configuration files for each specific error,
> + including the "default" behavior, which contains the same configuration
> + options as the specific errors.
> +
> + The available configurations for each error type are:
> +
> + max_retries (Min: -1 Default: -1 Max: INTMAX)
> + Define how many tries the filesystem is allowed to retry its
> + operations during the specific error, before shutdown the
> + filesystem. Setting this file to "-1", will set XFS to retry
> + forever in the specific error, setting it to "0", will make
> + XFS to fail immediately after the specific error is found,
> + while setting it to a "N" value, where N is greater than 0,
> + will make XFS retry "N" times before shutdown.
> +
> + 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. "0" means no wait time.
> +
> +
> + "max_retries" takes precedence over "retry_timeout_seconds", where,
> + "retry_timeout_seconds" will only be tested if the "max_retries" limit
> + were not reached yet or is set to retry forever ("-1"). If "max_retries"
> + limit is reached, the filesystem will shutdown, wether or not
> + "retry_timeout_seconds" has been reached.
> --
> 2.7.4
>
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