ext4 ext4_mount

ext4_mount

ext4 挂载函数，由具体的文件系统提供

static struct dentry *ext4_mount(struct file_system_type *fs_type, int flags,       const char *dev_name, void *data){return mount_bdev(fs_type, flags, dev_name, data, ext4_fill_super);}

struct dentry *mount_bdev(struct file_system_type *fs_type,int flags, const char *dev_name, void *data,int (*fill_super)(struct super_block *, void *, int)){struct block_device *bdev;struct super_block *s;fmode_t mode = FMODE_READ | FMODE_EXCL;int error = 0;if (!(flags & MS_RDONLY))mode |= FMODE_WRITE;获取设备bdev = blkdev_get_by_path(dev_name, mode, fs_type);if (IS_ERR(bdev))return ERR_CAST(bdev);/* * once the super is inserted into the list by sget, s_umount * will protect the lockfs code from trying to start a snapshot * while we are mounting */mutex_lock(&bdev->bd_fsfreeze_mutex);if (bdev->bd_fsfreeze_count > 0) {mutex_unlock(&bdev->bd_fsfreeze_mutex);error = -EBUSY;goto error_bdev;}s = sget(fs_type, test_bdev_super, set_bdev_super, flags | MS_NOSEC, bdev);mutex_unlock(&bdev->bd_fsfreeze_mutex);if (IS_ERR(s))goto error_s;if (s->s_root) {if ((flags ^ s->s_flags) & MS_RDONLY) {deactivate_locked_super(s);error = -EBUSY;goto error_bdev;}/* * s_umount nests inside bd_mutex during * __invalidate_device().  blkdev_put() acquires * bd_mutex and can't be called under s_umount.  Drop * s_umount temporarily.  This is safe as we're * holding an active reference. */up_write(&s->s_umount);blkdev_put(bdev, mode);down_write(&s->s_umount);} else {s->s_mode = mode;snprintf(s->s_id, sizeof(s->s_id), "%pg", bdev);sb_set_blocksize(s, block_size(bdev));error = fill_super(s, data, flags & MS_SILENT ? 1 : 0);if (error) {deactivate_locked_super(s);goto error;}s->s_flags |= MS_ACTIVE;bdev->bd_super = s;}return dget(s->s_root);error_s:error = PTR_ERR(s);error_bdev:blkdev_put(bdev, mode);error:return ERR_PTR(error);}