• Mike Snitzer's avatar
    dm table: set flush capability based on underlying devices · ed8b752b
    Mike Snitzer authored
    DM has always advertised both REQ_FLUSH and REQ_FUA flush capabilities
    regardless of whether or not a given DM device's underlying devices
    also advertised a need for them.
    
    Block's flush-merge changes from 2.6.39 have proven to be more costly
    for DM devices.  Performance regressions have been reported even when
    DM's underlying devices do not advertise that they have a write cache.
    
    Fix the performance regressions by configuring a DM device's flushing
    capabilities based on those of the underlying devices' capabilities.
    Signed-off-by: default avatarMike Snitzer <snitzer@redhat.com>
    Signed-off-by: default avatarAlasdair G Kergon <agk@redhat.com>
    ed8b752b
dm-table.c 33.7 KB