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nilfs2: add feature set fields to super block 

This adds three new fields to nilfs_super_block structure, compatible
feature set, readonly-compatible feature set, and incompatible feature
set in order to prepare for future disk format modifications.

The role of these fields conforms to those of ext3 or other
filesystems.  Most important flags are the incompatible feature set;
it is used to refuse to mount the filesystem which sets an
incompatible feature the kernel doesn't know about.

Signed-off-by: Ryusuke Konishi <konishi.ryusuke@lab.ntt.co.jp>
This commit is contained in:
Ryusuke Konishi 2010-07-22 03:22:19 +09:00
parent 2f1b7cd29f
commit 1a80a1763f
1 changed files with 14 additions and 1 deletions
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15
include/linux/nilfs2_fs.h
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@ -212,7 +212,10 @@ struct nilfs_super_block {
/*F8*/ __le32 s_c_interval; /* Commit interval of segment */
__le32 s_c_block_max; /* Threshold of data amount for
the segment construction */
__u32 s_reserved[192]; /* padding to the end of the block */
/*100*/ __le64 s_feature_compat; /* Compatible feature set */
__le64 s_feature_compat_ro; /* Read-only compatible feature set */
__le64 s_feature_incompat; /* Incompatible feature set */
__u32 s_reserved[186]; /* padding to the end of the block */
};
/*
@ -227,6 +230,16 @@ struct nilfs_super_block {
#define NILFS_CURRENT_REV 2 /* current major revision */
#define NILFS_MINOR_REV 0 /* minor revision */
/*
* Feature set definitions
*
* If there is a bit set in the incompatible feature set that the kernel
* doesn't know about, it should refuse to mount the filesystem.
*/
#define NILFS_FEATURE_COMPAT_SUPP 0ULL
#define NILFS_FEATURE_COMPAT_RO_SUPP 0ULL
#define NILFS_FEATURE_INCOMPAT_SUPP 0ULL
/*
* Bytes count of super_block for CRC-calculation
*/