• Christoph Hellwig's avatar
    block: introduce zoned block devices zone write locking · 6cc77e9c
    Christoph Hellwig authored
    Components relying only on the request_queue structure for accessing
    block devices (e.g. I/O schedulers) have a limited knowledged of the
    device characteristics. In particular, the device capacity cannot be
    easily discovered, which for a zoned block device also result in the
    inability to easily know the number of zones of the device (the zone
    size is indicated by the chunk_sectors field of the queue limits).
    
    Introduce the nr_zones field to the request_queue structure to simplify
    access to this information. Also, add the bitmap seq_zone_bitmap which
    indicates which zones of the device are sequential zones (write
    preferred or write required) and the bitmap seq_zones_wlock which
    indicates if a zone is write locked, that is, if a write request
    targeting a zone was dispatched to the device. These fields are
    initialized by the low level block device driver (sd.c for ZBC/ZAC
    disks). They are not initialized by stacking drivers (device mappers)
    handling zoned block devices (e.g. dm-linear).
    
    Using this, I/O schedulers can introduce zone write locking to control
    request dispatching to a zoned block device and avoid write request
    reordering by limiting to at most a single write request per zone
    outside of the scheduler at any time.
    
    Based on previous patches from Damien Le Moal.
    Signed-off-by: default avatarChristoph Hellwig <hch@lst.de>
    [Damien]
    * Fixed comments and identation in blkdev.h
    * Changed helper functions
    * Fixed this commit message
    Signed-off-by: default avatarDamien Le Moal <damien.lemoal@wdc.com>
    Reviewed-by: default avatarMartin K. Petersen <martin.petersen@oracle.com>
    Signed-off-by: default avatarJens Axboe <axboe@kernel.dk>
    6cc77e9c
blk-core.c 101 KB