• David Sterba's avatar
    btrfs: preallocate device flush bio · e0ae9994
    David Sterba authored
    For devices that support flushing, we allocate a bio, submit, wait for
    it and then free it. The bio allocation does not fail so ENOMEM is not a
    problem but we still may unnecessarily stress the allocation subsystem.
    
    Instead, we can allocate the bio at the same time we allocate the device
    and reuse it each time we need to flush the barriers. The bio is reset
    before each use. Reference counting is simplified to just device
    allocation (get) and freeing (put).
    
    The bio used to be submitted through the integrity checker which will
    find out that bio has no data attached and call submit_bio.
    
    Status of the bio in flight needs to be tracked separately in case the
    device caches get switched off between write and wait.
    Signed-off-by: default avatarDavid Sterba <dsterba@suse.com>
    e0ae9994
volumes.c 187 KB