• Brian Foster's avatar
    xfs: export log_recovery_delay to delay mount time log recovery · 2e227178
    Brian Foster authored
    XFS log recovery has been discovered to have race conditions with
    buffers when I/O errors occur. External tools are available to simulate
    I/O errors to XFS, but this alone is not sufficient for testing log
    recovery. XFS unconditionally resets the inactive region of the log
    prior to log recovery to avoid confusion over processing any partially
    written log records that might have been written before an unclean
    shutdown. Therefore, unconditional write I/O failures at mount time are
    caught by the reset sequence rather than log recovery and hinder the
    ability to test the latter.
    The device-mapper dm-flakey module uses an up/down timer to define a
    cycle for when to fail I/Os. Create a pre log recovery delay tunable
    that can be used to coordinate XFS log recovery with I/O errors
    simulated by dm-flakey. This facilitates coordination in userspace that
    allows the reset of stale log blocks to succeed and writes due to log
    recovery to fail. For example, define a dm-flakey instance with an
    uptime long enough to allow log reset to succeed and a log recovery
    delay long enough to allow the dm-flakey uptime to expire.
    The 'log_recovery_delay' sysfs tunable is exported under
    /sys/fs/xfs/debug and is only enabled for kernels compiled in XFS debug
    mode. The value is exported in units of seconds and allows for a delay
    of up to 60 seconds. Note that this is for XFS debug and test
    instrumentation purposes only and should not be used by applications. No
    delay is enabled by default.
    Signed-off-by: default avatarBrian Foster <bfoster@redhat.com>
    Reviewed-by: default avatarDave Chinner <dchinner@redhat.com>
    Signed-off-by: default avatarDave Chinner <david@fromorbit.com>
xfs_globals.c 1.7 KB