nilfs2: support nanosecond timestamp

After a review of user's feedback for finding out other compatibility
issues, I found nilfs improperly initializes timestamps in inode;
CURRENT_TIME was used there instead of CURRENT_TIME_SEC even though nilfs
didn't have nanosecond timestamps on disk.  A few users gave us the report
that the tar program sometimes failed to expand symbolic links on nilfs,
and it turned out to be the cause.

Instead of applying the above displacement, I've decided to support
nanosecond timestamps on this occation.  Fortunetaly, a needless 64-bit
field was in the nilfs_inode struct, and I found it's available for this
purpose without impact for the users.

So, this will do the enhancement and resolve the tar problem.

Signed-off-by: Ryusuke Konishi <konishi.ryusuke@lab.ntt.co.jp>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

4 files changed, 7 insertions, 9 deletions

diff --git a/fs/nilfs2/gcinode.c b/fs/nilfs2/gcinode.c
index 77615aa..19d2102 100644
--- a/fs/nilfs2/gcinode.c
+++ b/fs/nilfs2/gcinode.c
@@ -226,7 +226,6 @@ static struct inode *alloc_gcinode(struct the_nilfs *nilfs, ino_t ino,
 	ii->i_flags = 0;
 	ii->i_state = 1 << NILFS_I_GCINODE;
 	ii->i_bh = NULL;
-	ii->i_dtime = 0;
 	nilfs_bmap_init_gc(ii->i_bmap);
 
 	return inode;
diff --git a/fs/nilfs2/inode.c b/fs/nilfs2/inode.c
index a1922b1..49ab4a4 100644
--- a/fs/nilfs2/inode.c
+++ b/fs/nilfs2/inode.c
@@ -306,7 +306,6 @@ struct inode *nilfs_new_inode(struct inode *dir, int mode)
 
 	/* ii->i_file_acl = 0; */
 	/* ii->i_dir_acl = 0; */
-	ii->i_dtime = 0;
 	ii->i_dir_start_lookup = 0;
 #ifdef CONFIG_NILFS_FS_POSIX_ACL
 	ii->i_acl = NULL;
@@ -390,11 +389,10 @@ int nilfs_read_inode_common(struct inode *inode,
 	inode->i_atime.tv_sec = le64_to_cpu(raw_inode->i_mtime);
 	inode->i_ctime.tv_sec = le64_to_cpu(raw_inode->i_ctime);
 	inode->i_mtime.tv_sec = le64_to_cpu(raw_inode->i_mtime);
-	inode->i_atime.tv_nsec = 0;
-	inode->i_ctime.tv_nsec = 0;
-	inode->i_mtime.tv_nsec = 0;
-	ii->i_dtime = le64_to_cpu(raw_inode->i_dtime);
-	if (inode->i_nlink == 0 && (inode->i_mode == 0 || ii->i_dtime))
+	inode->i_atime.tv_nsec = le32_to_cpu(raw_inode->i_mtime_nsec);
+	inode->i_ctime.tv_nsec = le32_to_cpu(raw_inode->i_ctime_nsec);
+	inode->i_mtime.tv_nsec = le32_to_cpu(raw_inode->i_mtime_nsec);
+	if (inode->i_nlink == 0 && inode->i_mode == 0)
 		return -EINVAL; /* this inode is deleted */
 
 	inode->i_blocks = le64_to_cpu(raw_inode->i_blocks);
@@ -505,9 +503,10 @@ void nilfs_write_inode_common(struct inode *inode,
 	raw_inode->i_size = cpu_to_le64(inode->i_size);
 	raw_inode->i_ctime = cpu_to_le64(inode->i_ctime.tv_sec);
 	raw_inode->i_mtime = cpu_to_le64(inode->i_mtime.tv_sec);
+	raw_inode->i_ctime_nsec = cpu_to_le32(inode->i_ctime.tv_nsec);
+	raw_inode->i_mtime_nsec = cpu_to_le32(inode->i_mtime.tv_nsec);
 	raw_inode->i_blocks = cpu_to_le64(inode->i_blocks);
 
-	raw_inode->i_dtime = cpu_to_le64(ii->i_dtime);
 	raw_inode->i_flags = cpu_to_le32(ii->i_flags);
 	raw_inode->i_generation = cpu_to_le32(inode->i_generation);
 
diff --git a/fs/nilfs2/nilfs.h b/fs/nilfs2/nilfs.h
index 19af5ab..7558c97 100644
--- a/fs/nilfs2/nilfs.h
+++ b/fs/nilfs2/nilfs.h
@@ -48,7 +48,6 @@ struct nilfs_inode_info {
 	struct nilfs_bmap *i_bmap;
 	union nilfs_bmap_union i_bmap_union;
 	__u64 i_xattr;	/* sector_t ??? */
-	__u32 i_dtime;
 	__u32 i_dir_start_lookup;
 	__u64 i_cno;		/* check point number for GC inode */
 	struct address_space i_btnode_cache;
diff --git a/fs/nilfs2/super.c b/fs/nilfs2/super.c
index e2ced82..e117e1e 100644
--- a/fs/nilfs2/super.c
+++ b/fs/nilfs2/super.c
@@ -792,6 +792,7 @@ nilfs_fill_super(struct super_block *sb, void *data, int silent,
 	sb->s_op = &nilfs_sops;
 	sb->s_export_op = &nilfs_export_ops;
 	sb->s_root = NULL;
+	sb->s_time_gran = 1;
 
 	if (!nilfs_loaded(nilfs)) {
 		err = load_nilfs(nilfs, sbi);