Linux中文件系统注册及mount过程分析5

通过这个fill_super来进行读读块设备

2545 static int ext4_fill_super(struct super_block *sb, void *data, intsilent)
2546 __releases(kernel_lock)
2547 __acquires(kernel_lock)
2548 {
2549 char *orig_data = kstrdup(data, GFP_KERNEL);
2550 struct buffer_head *bh;
2551 struct ext4_super_block *es = NULL;
2552 struct ext4_sb_info *sbi;
2553 ext4_fsblk_t block;
2554 ext4_fsblk_t sb_block = get_sb_block(&data);
2555 ext4_fsblk_t logical_sb_block;
2556 unsigned long offset = 0;
……
2580 }
2581 sb->s_fs_info = sbi;
2582 sbi->s_mount_opt = 0;
2583 sbi->s_resuid = EXT4_DEF_RESUID;
2584 sbi->s_resgid = EXT4_DEF_RESGID;
2585 sbi->s_inode_readahead_blks = EXT4_DEF_INODE_READAHEAD_BLKS;
2586 sbi->s_sb_block = sb_block;
2587 if (sb->s_bdev->bd_part)
2588 sbi->s_sectors_written_start =
2589 part_stat_read(sb->s_bdev->bd_part, sectors[1]);
2590
2591 unlock_kernel();
2592
2593 /* Cleanup superblock name */
2594 for (cp = sb->s_id; (cp = strchr(cp, '/'));)
2595 *cp = '!';
2596
2597 ret = -EINVAL;
2598 blocksize = sb_min_blocksize(sb, EXT4_MIN_BLOCK_SIZE);
2599 if (!blocksize) {
2600 ext4_msg(sb, KERN_ERR, "unable to set blocksize");
2601 goto out_fail;
2602 }
2603
2604 /*
2605 * The ext4 superblock will not be buffer aligned for other than 1kB
2606 * block sizes. We need to calculate the offset from buffer start.
2607 */
2608 if (blocksize != EXT4_MIN_BLOCK_SIZE) {
2609 logical_sb_block = sb_block * EXT4_MIN_BLOCK_SIZE;
2610 offset = do_div(logical_sb_block, blocksize);
2611 } else {
2612 logical_sb_block = sb_block;
2613 }
2614
2615 if (!(bh = sb_bread(sb, logical_sb_block))) {
2616 ext4_msg(sb, KERN_ERR, "unable to read superblock");
2617 goto out_fail;
2618 }
……
2649 if ((def_mount_opts & EXT4_DEFM_JMODE) == EXT4_DEFM_JMODE_DATA)
2650 set_opt(sbi->s_mount_opt, JOURNAL_DATA);
2651 else if ((def_mount_opts & EXT4_DEFM_JMODE) == EXT4_DEFM_JMODE_ORDERED)
2652 set_opt(sbi->s_mount_opt, ORDERED_DATA);
2653 else if ((def_mount_opts & EXT4_DEFM_JMODE) == EXT4_DEFM_JMODE_WBACK)
2654 set_opt(sbi->s_mount_opt, WRITEBACK_DATA);
2655
2656 if (le16_to_cpu(sbi->s_es->s_errors) == EXT4_ERRORS_PANIC)
2657 set_opt(sbi->s_mount_opt, ERRORS_PANIC);
2658 else if (le16_to_cpu(sbi->s_es->s_errors) == EXT4_ERRORS_CONTINUE)
2659 set_opt(sbi->s_mount_opt, ERRORS_CONT);
2660 else
2661 set_opt(sbi->s_mount_opt, ERRORS_RO);
2662 if (def_mount_opts & EXT4_DEFM_BLOCK_VALIDITY)
2663 set_opt(sbi->s_mount_opt, BLOCK_VALIDITY);
2664 if (def_mount_opts & EXT4_DEFM_DISCARD)
2665 set_opt(sbi->s_mount_opt, DISCARD);
……
2931 * set up enough so that it can read an inode
2932 */
2933 if (!test_opt(sb, NOLOAD) &&
2934 EXT4_HAS_COMPAT_FEATURE(sb, EXT4_FEATURE_COMPAT_HAS_JOURNAL))
2935 sb->s_op = &ext4_sops;
2936 else
2937 sb->s_op = &ext4_nojournal_sops;
2938 sb->s_export_op = &ext4_export_ops;
2939 sb->s_xattr = ext4_xattr_handlers;
2940 #ifdef CONFIG_QUOTA
2941 sb->s_qcop = &ext4_qctl_operations;
2942 sb->dq_op = &ext4_quota_operations;
2943 #endif
……
3052 root = ext4_iget(sb, EXT4_ROOT_INO);
3053 if (IS_ERR(root)) {
3054 ext4_msg(sb, KERN_ERR, "get root inode failed");
3055 ret = PTR_ERR(root);
3056 goto failed_mount4;
3057 }
3058 if (!S_ISDIR(root->i_mode) || !root->i_blocks || !root->i_size) {
3059 iput(root);
3060 ext4_msg(sb, KERN_ERR, "corrupt root inode, run e2fsck");
3061 goto failed_mount4;
3062 }
3063 sb->s_root = d_alloc_root(root);
3064 if (!sb->s_root) {
3065 ext4_msg(sb, KERN_ERR, "get root dentry failed");
3066 iput(root);
3067 ret = -ENOMEM;
3068 goto failed_mount4;
3069 }
3070
3071 ext4_setup_super(sb, es, sb->s_flags & MS_RDONLY);
3072

这些介绍了从读超级快，获得磁盘的块的属性，然后进行了sops注册，然后进入ext4_iget进行了文件操作，目录操作，链接操作等函数的注册，比如读文件

然后回到do_new_mount，将挂载点添加到列表里就可以了，这个列表在/proc中可以展现出来

[root@T-bagwell ~]# cat /proc/mounts
rootfs / rootfs rw 0 0
/dev/root / ext4 rw,relatime,barrier=1,data=ordered 0 0
/dev /dev tmpfs rw,relatime,mode=755 0 0
/proc /proc proc rw,relatime 0 0
/sys /sys sysfs rw,relatime 0 0
/proc/bus/usb /proc/bus/usb usbfs rw,relatime 0 0
devpts /dev/pts devpts rw,relatime,gid=5,mode=620,ptmxmode=000 0 0
none /proc/sys/fs/binfmt_misc binfmt_misc rw,relatime 0 0
sunrpc /var/lib/nfs/rpc_pipefs rpc_pipefs rw,relatime 0 0
/dev/sdb1 /media/android ext4 rw,relatime,barrier=1,data=ordered 0 0
[root@T-bagwell ~]#

到这里文件系统的注册和磁盘的挂载完成