第13章 Linux块设备驱动 疑问

1，分散/聚集（SG，scatter/gather）操作？
       http://blog.chinaunix.net/space.php?uid=20774181&do=blog&id=1847063，
       我不得不感叹，百度都没有站内搜索好用。多谢CUers！

2，看看内核block目录
      其中，Makefile内容为：（然后就迷茫了，初始block驱动！）

#
# Makefile for the kernel block layer
#

obj-$(CONFIG_BLOCK) := elevator.o blk-core.o blk-tag.o blk-sysfs.o \
blk-barrier.o blk-settings.o blk-ioc.o blk-map.o \
blk-exec.o blk-merge.o blk-softirq.o blk-timeout.o \
blk-iopoll.o blk-lib.o ioctl.o genhd.o scsi_ioctl.o

obj-$(CONFIG_BLK_DEV_BSG)	+= bsg.o
obj-$(CONFIG_BLK_CGROUP)	+= blk-cgroup.o
obj-$(CONFIG_IOSCHED_NOOP)	+= noop-iosched.o
obj-$(CONFIG_IOSCHED_DEADLINE)	+= deadline-iosched.o
obj-$(CONFIG_IOSCHED_CFQ)	+= cfq-iosched.o

obj-$(CONFIG_BLOCK_COMPAT)	+= compat_ioctl.o
obj-$(CONFIG_BLK_DEV_INTEGRITY)	+= blk-integrity.o

3，“反弹”缓冲区？？
       我晕，在书里找不到了。看来下次还是得记下页码。没有找到所谓的“反弹”缓冲区的感念，看来有些理解不能脱离上下文，不一定是标准的。

4，struct block_device
       在源码/include/linux/fs.h中：

struct block_device {
    dev_t            bd_dev;  /* not a kdev_t - it's a search key */
    struct inode *        bd_inode;    /* will die */
    struct super_block *    bd_super;
    int            bd_openers;
    struct mutex        bd_mutex;    /* open/close mutex */
    struct list_head    bd_inodes;
    void *            bd_claiming;
    void *            bd_holder;
    int            bd_holders;
#ifdef CONFIG_SYSFS
    struct list_head    bd_holder_list;
#endif
    struct block_device *    bd_contains;
    unsigned        bd_block_size;
    struct hd_struct *    bd_part;
    /* number of times partitions within this device have been opened. */
    unsigned        bd_part_count;
    int            bd_invalidated;
    struct gendisk *    bd_disk;
    struct list_head    bd_list;
    /*
     * Private data.  You must have bd_claim'ed the block_device
     * to use this.  NOTE:  bd_claim allows an owner to claim
     * the same device multiple times, the owner must take special
     * care to not mess up bd_private for that case.
     */
    unsigned long        bd_private;

    /* The counter of freeze processes */
    int            bd_fsfreeze_count;
    /* Mutex for freeze */
    struct mutex        bd_fsfreeze_mutex;
};

5，drivers/block/floppy.c

6，inode, vnode, blocks？？？
       这个帖子还不错！
       难道对于Unix系列的操作系统，大多都有v节点。但是对于linux来说，只有通用的i节点，却没有v节点吗？？？

7，书内vmem_disk的驱动？？？？
      #遗留问题啊~~~~

8，硬盘基本知识（磁道、扇区、柱面、磁头数、簇、MBR、DBR）？
     

9，块设备的读写，核心是“请求处理函数  和   请求'制造'函数”？
      那么块设备的读写是怎么完成的呢？靠映射，由内核其它部分来处理……真心没有搞懂！