[RFC PATCH] nilfs2: introduce atime support

[Viacheslav Dubeyko <slava@dubeyko.com>]

Currently, NILFS2 doesn't support atime. And it is possible
to see the evidence of it by running generic/003 test-case of
xfstests suite:

sudo ./check generic/003
FSTYP -- nilfs2
PLATFORM -- Linux/x86_64 hfsplus-testing-0001 6.18.0-rc1+ #10 SMP PREEMPT_DYNAMIC Fri Nov 28 20:48:25 PST 2025
MKFS_OPTIONS -- /dev/loop51
MOUNT_OPTIONS -- /dev/loop51 /mnt/scratch

generic/003 35s ... - output mismatch (see xfstests-dev/results//generic/003.out.bad)

This patch exchanges i_xattr on i_atime and i_pad
on i_atime_nsec fields of struct nilfs_inode in
the on-disk layout, removes all declarations that
disabled atime support. Also, it modifies
nilfs_read_inode_common(), nilfs_write_inode_common(),
and nilfs_setattr() with the goal of proper atime
support.

sudo ./check generic/003
FSTYP         -- nilfs2
PLATFORM      -- Linux/x86_64 nilfs2-testing 6.19.0-rc1+ #8 SMP PREEMPT_DYNAMIC Tue Feb 17 16:21:59 PST 2026
MKFS_OPTIONS  -- /dev/loop51
MOUNT_OPTIONS -- /dev/loop51 /mnt/scratch

generic/003  30s ...  34s
Ran: generic/003
Passed all 1 tests

[1] https://github.com/nilfs-dev/nilfs2/issues/7

Signed-off-by: Viacheslav Dubeyko <slava@dubeyko.com>
---
 fs/nilfs2/Kconfig                  |  2 +-
 fs/nilfs2/inode.c                  | 18 ++++++++++++++----
 fs/nilfs2/nilfs.h                  |  8 ++------
 fs/nilfs2/segment.c                |  2 --
 fs/nilfs2/super.c                  |  5 -----
 include/uapi/linux/nilfs2_ondisk.h |  8 ++++----
 6 files changed, 21 insertions(+), 22 deletions(-)

diff --git a/fs/nilfs2/Kconfig b/fs/nilfs2/Kconfig
index 7dae168e346e..28de0967745c 100644
--- a/fs/nilfs2/Kconfig
+++ b/fs/nilfs2/Kconfig
@@ -20,7 +20,7 @@ config NILFS2_FS
 	  snapshot is mountable as a read-only file system concurrently with
 	  its writable mount, and this feature is convenient for online backup.
 
-	  Some features including atime, extended attributes, and POSIX ACLs,
+	  Some features including extended attributes, and POSIX ACLs,
 	  are not supported yet.
 
 	  To compile this file system support as a module, choose M here: the
diff --git a/fs/nilfs2/inode.c b/fs/nilfs2/inode.c
index 51bde45d5865..a6fcd8133501 100644
--- a/fs/nilfs2/inode.c
+++ b/fs/nilfs2/inode.c
@@ -395,8 +395,8 @@ void nilfs_set_inode_flags(struct inode *inode)
 		new_fl |= S_NOATIME;
 	if (flags & FS_DIRSYNC_FL)
 		new_fl |= S_DIRSYNC;
-	inode_set_flags(inode, new_fl, S_SYNC | S_APPEND | S_IMMUTABLE |
-			S_NOATIME | S_DIRSYNC);
+	inode_set_flags(inode, new_fl,
+			S_SYNC | S_APPEND | S_IMMUTABLE | S_DIRSYNC);
 }
 
 int nilfs_read_inode_common(struct inode *inode,
@@ -410,12 +410,13 @@ int nilfs_read_inode_common(struct inode *inode,
 	i_gid_write(inode, le32_to_cpu(raw_inode->i_gid));
 	set_nlink(inode, le16_to_cpu(raw_inode->i_links_count));
 	inode->i_size = le64_to_cpu(raw_inode->i_size);
-	inode_set_atime(inode, le64_to_cpu(raw_inode->i_mtime),
-			le32_to_cpu(raw_inode->i_mtime_nsec));
+	inode_set_atime(inode, le64_to_cpu(raw_inode->i_atime),
+			le32_to_cpu(raw_inode->i_atime_nsec));
 	inode_set_ctime(inode, le64_to_cpu(raw_inode->i_ctime),
 			le32_to_cpu(raw_inode->i_ctime_nsec));
 	inode_set_mtime(inode, le64_to_cpu(raw_inode->i_mtime),
 			le32_to_cpu(raw_inode->i_mtime_nsec));
+
 	if (nilfs_is_metadata_file_inode(inode) && !S_ISREG(inode->i_mode))
 		return -EIO; /* this inode is for metadata and corrupted */
 	if (inode->i_nlink == 0)
@@ -723,8 +724,10 @@ void nilfs_write_inode_common(struct inode *inode,
 	raw_inode->i_gid = cpu_to_le32(i_gid_read(inode));
 	raw_inode->i_links_count = cpu_to_le16(inode->i_nlink);
 	raw_inode->i_size = cpu_to_le64(inode->i_size);
+	raw_inode->i_atime = cpu_to_le64(inode_get_atime_sec(inode));
 	raw_inode->i_ctime = cpu_to_le64(inode_get_ctime_sec(inode));
 	raw_inode->i_mtime = cpu_to_le64(inode_get_mtime_sec(inode));
+	raw_inode->i_atime_nsec = cpu_to_le32(inode_get_atime_nsec(inode));
 	raw_inode->i_ctime_nsec = cpu_to_le32(inode_get_ctime_nsec(inode));
 	raw_inode->i_mtime_nsec = cpu_to_le32(inode_get_mtime_nsec(inode));
 	raw_inode->i_blocks = cpu_to_le64(inode->i_blocks);
@@ -929,6 +932,13 @@ int nilfs_setattr(struct mnt_idmap *idmap, struct dentry *dentry,
 		nilfs_truncate(inode);
 	}
 
+	if (iattr->ia_valid & ATTR_ATIME)
+		inode_set_atime_to_ts(inode, iattr->ia_atime);
+	if (iattr->ia_valid & ATTR_MTIME)
+		inode_set_mtime_to_ts(inode, iattr->ia_mtime);
+	if (iattr->ia_valid & ATTR_CTIME)
+		inode_set_ctime_to_ts(inode, iattr->ia_ctime);
+
 	setattr_copy(&nop_mnt_idmap, inode, iattr);
 	mark_inode_dirty(inode);
 
diff --git a/fs/nilfs2/nilfs.h b/fs/nilfs2/nilfs.h
index b7e3d91b6243..c78a06883490 100644
--- a/fs/nilfs2/nilfs.h
+++ b/fs/nilfs2/nilfs.h
@@ -27,7 +27,6 @@
  * @i_state: dynamic state flags
  * @i_bmap: pointer on i_bmap_data
  * @i_bmap_data: raw block mapping
- * @i_xattr: <TODO>
  * @i_dir_start_lookup: page index of last successful search
  * @i_cno: checkpoint number for GC inode
  * @i_assoc_inode: associated inode (B-tree node cache holder or back pointer)
@@ -43,7 +42,6 @@ struct nilfs_inode_info {
 	unsigned long  i_state;		/* Dynamic state flags */
 	struct nilfs_bmap *i_bmap;
 	struct nilfs_bmap i_bmap_data;
-	__u64 i_xattr;	/* sector_t ??? */
 	__u32 i_dir_start_lookup;
 	__u64 i_cno;		/* check point number for GC inode */
 	struct inode *i_assoc_inode;
@@ -234,12 +232,10 @@ static inline int nilfs_init_acl(struct inode *inode, struct inode *dir)
 }
 #endif
 
-#define NILFS_ATIME_DISABLE
-
 /* Flags that should be inherited by new inodes from their parent. */
 #define NILFS_FL_INHERITED						\
 	(FS_SECRM_FL | FS_UNRM_FL | FS_COMPR_FL | FS_SYNC_FL |		\
-	 FS_IMMUTABLE_FL | FS_APPEND_FL | FS_NODUMP_FL | FS_NOATIME_FL |\
+	 FS_IMMUTABLE_FL | FS_APPEND_FL | FS_NODUMP_FL |		\
 	 FS_COMPRBLK_FL | FS_NOCOMP_FL | FS_NOTAIL_FL | FS_DIRSYNC_FL)
 
 /* Mask out flags that are inappropriate for the given type of inode. */
@@ -250,7 +246,7 @@ static inline __u32 nilfs_mask_flags(umode_t mode, __u32 flags)
 	else if (S_ISREG(mode))
 		return flags & ~(FS_DIRSYNC_FL | FS_TOPDIR_FL);
 	else
-		return flags & (FS_NODUMP_FL | FS_NOATIME_FL);
+		return flags & FS_NODUMP_FL;
 }
 
 /* dir.c */
diff --git a/fs/nilfs2/segment.c b/fs/nilfs2/segment.c
index deee16bc9d4e..fae3274e354b 100644
--- a/fs/nilfs2/segment.c
+++ b/fs/nilfs2/segment.c
@@ -930,8 +930,6 @@ static void nilfs_write_root_mdt_inode(struct inode *inode,
 	nilfs_write_inode_common(inode, raw_inode);
 
 	/* zero-fill unused portion of raw_inode */
-	raw_inode->i_xattr = 0;
-	raw_inode->i_pad = 0;
 	memset((void *)raw_inode + sizeof(*raw_inode), 0,
 	       nilfs->ns_inode_size - sizeof(*raw_inode));
 
diff --git a/fs/nilfs2/super.c b/fs/nilfs2/super.c
index badc2cbc895e..824d71cbbd8d 100644
--- a/fs/nilfs2/super.c
+++ b/fs/nilfs2/super.c
@@ -867,11 +867,6 @@ int nilfs_store_magic(struct super_block *sb,
 
 	sb->s_magic = le16_to_cpu(sbp->s_magic);
 
-	/* FS independent flags */
-#ifdef NILFS_ATIME_DISABLE
-	sb->s_flags |= SB_NOATIME;
-#endif
-
 	nilfs->ns_resuid = le16_to_cpu(sbp->s_def_resuid);
 	nilfs->ns_resgid = le16_to_cpu(sbp->s_def_resgid);
 	nilfs->ns_interval = le32_to_cpu(sbp->s_c_interval);
diff --git a/include/uapi/linux/nilfs2_ondisk.h b/include/uapi/linux/nilfs2_ondisk.h
index b3442b16ff6a..26a1ef28bc66 100644
--- a/include/uapi/linux/nilfs2_ondisk.h
+++ b/include/uapi/linux/nilfs2_ondisk.h
@@ -47,9 +47,9 @@
  * @i_links_count: links count
  * @i_flags: file flags
  * @i_bmap: block mapping
- * @i_xattr: extended attributes
+ * @i_atime: access time (seconds)
  * @i_generation: file generation (for NFS)
- * @i_pad: padding
+ * @i_atime_nsec: access time (nano seconds)
  */
 struct nilfs_inode {
 	__le64	i_blocks;
@@ -65,9 +65,9 @@ struct nilfs_inode {
 	__le32	i_flags;
 	__le64	i_bmap[NILFS_INODE_BMAP_SIZE];
 #define i_device_code	i_bmap[0]
-	__le64	i_xattr;
+	__le64	i_atime;
 	__le32	i_generation;
-	__le32	i_pad;
+	__le32	i_atime_nsec;
 };
 
 #define NILFS_MIN_INODE_SIZE		128
-- 
2.43.0