• inode state bits

History of inode state bits

Linux 2.0.1:

/* nothing */

Linux 2.2.0:

/* Inode state bits.. */
#define I_DIRTY         1
#define I_LOCK          2
#define I_FREEING       4

Linux 2.3.47:

/* Inode state bits.. */
#define I_DIRTY         1
#define I_LOCK          2
#define I_FREEING       4
#define I_CLEAR         8

Linux 2.4.0-test12:

/* Inode state bits.. */ 
#define I_DIRTY_SYNC            1 /* Not dirty enough for O_DATASYNC */ 
#define I_DIRTY_DATASYNC        2 /* Data-related inode changes pending */ 
#define I_LOCK                  4 
#define I_FREEING               8 
#define I_CLEAR                 16 

Splitting I_DIRTY_SYNC and I_DIRTY_DATASYNC allows fdatasync() to skip inodes that only have atime changed.

Linux 2.4.0-prerelease:

/* Inode state bits.. */
#define I_DIRTY_SYNC            1 /* Not dirty enough for O_DATASYNC */
#define I_DIRTY_DATASYNC        2 /* Data-related inode changes pending */
#define I_DIRTY_PAGES           4 /* Data-related inode changes pending */
#define I_LOCK                  8
#define I_FREEING               16
#define I_CLEAR                 32

I_DIRTY_PAGES allow filesystems to skip writing inodes if the inode itself was never changed, but only data pages.