• Darrick J. Wong's avatar
    xfs: create shadow transaction reservations for computing minimum log size · 52d8ea4f
    Darrick J. Wong authored
    Every time someone changes the transaction reservation sizes, they
    introduce potential compatibility problems if the changes affect the
    minimum log size that we validate at mount time.  If the minimum log
    size gets larger (which should be avoided because doing so presents a
    serious risk of log livelock), filesystems created with old mkfs will
    not mount on a newer kernel; if the minimum size shrinks, filesystems
    created with newer mkfs will not mount on older kernels.
    
    Therefore, enable the creation of a shadow log reservation structure
    where we can "undo" the effects of tweaks when computing minimum log
    sizes.  These shadow reservations should never be used in practice, but
    they insulate us from perturbations in minimum log size.
    Signed-off-by: default avatarDarrick J. Wong <djwong@kernel.org>
    Reviewed-by: default avatarDave Chinner <dchinner@redhat.com>
    Reviewed-by: default avatarChristoph Hellwig <hch@lst.de>
    52d8ea4f
xfs_log_rlimit.c 4.19 KB