[PATCH v2] erofs: rename ctime to mtime

[Gao Xiang <hsiangkao@linux.alibaba.com>]

From: David Anderson <dvander@google.com>

EROFS images should inherit modification time rather than change time,
since users and host tooling have no easy way to control change time.

To reflect the new timestamp meaning, i_ctime and i_ctime_nsec are
renamed to i_mtime and i_mtime_nsec.

Signed-off-by: David Anderson <dvander@google.com>
[ Gao Xiang: update document as well. ]
Signed-off-by: Gao Xiang <hsiangkao@linux.alibaba.com>
---
If no other concerns, I will apply it for 5.18.

 Documentation/filesystems/erofs.rst | 2 +-
 fs/erofs/erofs_fs.h                 | 5 +++--
 fs/erofs/inode.c                    | 4 ++--
 3 files changed, 6 insertions(+), 5 deletions(-)

diff --git a/Documentation/filesystems/erofs.rst b/Documentation/filesystems/erofs.rst
index 7119aa213be7..bef6d3040ce4 100644
--- a/Documentation/filesystems/erofs.rst
+++ b/Documentation/filesystems/erofs.rst
@@ -40,7 +40,7 @@ Here is the main features of EROFS:
    Inode metadata size    32 bytes      64 bytes
    Max file size          4 GB          16 EB (also limited by max. vol size)
    Max uids/gids          65536         4294967296
-   File change time       no            yes (64 + 32-bit timestamp)
+   Per-inode timestamp    no            yes (64 + 32-bit timestamp)
    Max hardlinks          65536         4294967296
    Metadata reserved      4 bytes       14 bytes
    =====================  ============  =====================================
diff --git a/fs/erofs/erofs_fs.h b/fs/erofs/erofs_fs.h
index 3ea62c6fb00a..1238ca104f09 100644
--- a/fs/erofs/erofs_fs.h
+++ b/fs/erofs/erofs_fs.h
@@ -12,6 +12,7 @@
 #define EROFS_SUPER_OFFSET      1024
 
 #define EROFS_FEATURE_COMPAT_SB_CHKSUM          0x00000001
+#define EROFS_FEATURE_COMPAT_MTIME              0x00000002
 
 /*
  * Any bits that aren't in EROFS_ALL_FEATURE_INCOMPAT should
@@ -186,8 +187,8 @@ struct erofs_inode_extended {
 
 	__le32 i_uid;
 	__le32 i_gid;
-	__le64 i_ctime;
-	__le32 i_ctime_nsec;
+	__le64 i_mtime;
+	__le32 i_mtime_nsec;
 	__le32 i_nlink;
 	__u8   i_reserved2[16];
 };
diff --git a/fs/erofs/inode.c b/fs/erofs/inode.c
index ff62f84f47d3..e8b37ba5e9ad 100644
--- a/fs/erofs/inode.c
+++ b/fs/erofs/inode.c
@@ -113,8 +113,8 @@ static void *erofs_read_inode(struct erofs_buf *buf,
 		set_nlink(inode, le32_to_cpu(die->i_nlink));
 
 		/* extended inode has its own timestamp */
-		inode->i_ctime.tv_sec = le64_to_cpu(die->i_ctime);
-		inode->i_ctime.tv_nsec = le32_to_cpu(die->i_ctime_nsec);
+		inode->i_ctime.tv_sec = le64_to_cpu(die->i_mtime);
+		inode->i_ctime.tv_nsec = le32_to_cpu(die->i_mtime_nsec);
 
 		inode->i_size = le64_to_cpu(die->i_size);
 
-- 
2.24.4