• Dave Chinner's avatar
    xfs: use generic percpu counters for inode counter · 501ab323
    Dave Chinner authored
    XFS has hand-rolled per-cpu counters for the superblock since before
    there was any generic implementation. There are some warts around
    the  use of them for the inode counter as the hand rolled counter is
    designed to be accurate at zero, but has no specific accurracy at
    any other value. This design causes problems for the maximum inode
    count threshold enforcement, as there is no trigger that balances
    the counters as they get close tothe maximum threshold.
    
    Instead of designing new triggers for balancing, just replace the
    handrolled per-cpu counter with a generic counter.  This enables us
    to update the counter through the normal superblock modification
    funtions, but rather than do that we add a xfs_mod_icount() helper
    function (from Christoph Hellwig) and keep the percpu counter
    outside the superblock in the struct xfs_mount.
    
    This means we still need to initialise the per-cpu counter
    specifically when we read the superblock, and vice versa when we
    log/write it, but it does mean that we don't need to change any
    other code.
    Signed-off-by: 's avatarDave Chinner <dchinner@redhat.com>
    Reviewed-by: 's avatarBrian Foster <bfoster@redhat.com>
    Signed-off-by: 's avatarDave Chinner <david@fromorbit.com>
    501ab323
xfs_trans.c 28 KB