• Dan Williams's avatar
    block: generic request_queue reference counting · 3ef28e83
    Dan Williams authored
    Allow pmem, and other synchronous/bio-based block drivers, to fallback
    on a per-cpu reference count managed by the core for tracking queue
    live/dead state.
    
    The existing per-cpu reference count for the blk_mq case is promoted to
    be used in all block i/o scenarios.  This involves initializing it by
    default, waiting for it to drop to zero at exit, and holding a live
    reference over the invocation of q->make_request_fn() in
    generic_make_request().  The blk_mq code continues to take its own
    reference per blk_mq request and retains the ability to freeze the
    queue, but the check that the queue is frozen is moved to
    generic_make_request().
    
    This fixes crash signatures like the following:
    
     BUG: unable to handle kernel paging request at ffff880140000000
     [..]
     Call Trace:
      [<ffffffff8145e8bf>] ? copy_user_handle_tail+0x5f/0x70
      [<ffffffffa004e1e0>] pmem_do_bvec.isra.11+0x70/0xf0 [nd_pmem]
      [<ffffffffa004e331>] pmem_make_request+0xd1/0x200 [nd_pmem]
      [<ffffffff811c3162>] ? mempool_alloc+0x72/0x1a0
      [<ffffffff8141f8b6>] generic_make_request+0xd6/0x110
      [<ffffffff8141f966>] submit_bio+0x76/0x170
      [<ffffffff81286dff>] submit_bh_wbc+0x12f/0x160
      [<ffffffff81286e62>] submit_bh+0x12/0x20
      [<ffffffff813395bd>] jbd2_write_superblock+0x8d/0x170
      [<ffffffff8133974d>] jbd2_mark_journal_empty+0x5d/0x90
      [<ffffffff813399cb>] jbd2_journal_destroy+0x24b/0x270
      [<ffffffff810bc4ca>] ? put_pwq_unlocked+0x2a/0x30
      [<ffffffff810bc6f5>] ? destroy_workqueue+0x225/0x250
      [<ffffffff81303494>] ext4_put_super+0x64/0x360
      [<ffffffff8124ab1a>] generic_shutdown_super+0x6a/0xf0
    
    Cc: Jens Axboe <axboe@kernel.dk>
    Cc: Keith Busch <keith.busch@intel.com>
    Cc: Ross Zwisler <ross.zwisler@linux.intel.com>
    Suggested-by: default avatarChristoph Hellwig <hch@lst.de>
    Reviewed-by: default avatarChristoph Hellwig <hch@lst.de>
    Tested-by: default avatarRoss Zwisler <ross.zwisler@linux.intel.com>
    Signed-off-by: default avatarDan Williams <dan.j.williams@intel.com>
    Signed-off-by: default avatarJens Axboe <axboe@fb.com>
    3ef28e83
blk-mq-sysfs.c 10.9 KB