Filesystems “如何存储”；“扩展属性”；在ext4 inode块中，我们有inode extra size“；我“额外的”；

依照

考虑到我使用的inode size=256字节，我发现这可以用来存储扩展属性。几个问题：

我如何知道我的FS索引节点大小是256字节还是128字节

如何设置小的扩展属性( 我如何知道我的FS索引节点大小是256字节还是128字节

如何设置小的扩展属性

Ext3/4支持可配置的inode大小（从-I选项mkfs.ext{3,4}cmd参数），但默认inode大小为128字节。Ext4将默认为256字节。这需要容纳一些额外字段（如纳秒时间戳或inode版本控制），并且inode的剩余空间将用于存储足够小的扩展属性，以适应该空间。此外，您可能希望查看fs/ext4/file.c:struct inode_operations{.setattr、.getattr}实现的函数

FileSystem/C lib对此有何调用

请参阅API以设置扩展属性。使用命令

attr、lsattr、chattr

测试集合文件上的扩展属性。您可能还需要

在128字节的inode之后映射额外字节的内存结构是什么，我想在这里存储我的小扩展属性

提及

"

---

“

lsattr

和

chattr

操作

无符号int i_标志；

struc inode字段，因此与

xattr

关系不大。请参阅和

/usr/include/linux/fs.h

struct ext4_inode {
  .....
  __le16  i_extra_isize;
  .....
}

$ sudo tune2fs -l /dev/sda2  | egrep -i 'inode size'
Inode size:               256

* Extended attributes are stored directly in inodes (on file systems with
 18  * inodes bigger than 128 bytes) and on additional disk blocks. The i_file_acl
 19  * field contains the block number if an inode uses an additional block. All
 20  * attributes must fit in the inode and one additional block. Blocks that
 21  * contain the identical set of attributes may be shared among several inodes.
 22  * Identical blocks are detected by keeping a cache of blocks that have
 23  * recently been accessed.
 24  *
 25  * The attributes in inodes and on blocks have a different header; the entries
 26  * are stored in the same format:
 27  *
 28  *   +------------------+
 29  *   | header           |
 30  *   | entry 1          | |
 31  *   | entry 2          | | growing downwards
 32  *   | entry 3          | v
 33  *   | four null bytes  |
 34  *   | . . .            |
 35  *   | value 1          | ^
 36  *   | value 3          | | growing upwards
 37  *   | value 2          | |
 38  *   +------------------+
 39  *
 40  * The header is followed by multiple entry descriptors. In disk blocks, the
 41  * entry descriptors are kept sorted. In inodes, they are unsorted. The
 42  * attribute values are aligned to the end of the block in no specific order.