fat: report creation time in statx

creation time is no longer mixed with change time.  Add an in-memory field
for it, and report it in statx if supported.

Link: https://lkml.kernel.org/r/20220503152536.2503003-3-cccheng@synology.com
Signed-off-by: Chung-Chiang Cheng <cccheng@synology.com>
Acked-by: OGAWA Hirofumi <hirofumi@mail.parknet.co.jp>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

fs/fat/fat.h

@@ -126,6 +126,7 @@ struct msdos_inode_info {
 	struct hlist_node i_fat_hash;	/* hash by i_location */
 	struct hlist_node i_dir_hash;	/* hash by i_logstart */
 	struct rw_semaphore truncate_lock; /* protect bmap against truncate */
+	struct timespec64 i_crtime;	/* File creation (birth) time */
 	struct inode vfs_inode;
 };
 

fs/fat/file.c

@@ -399,13 +399,21 @@ int fat_getattr(struct user_namespace *mnt_userns, const struct path *path,
 		struct kstat *stat, u32 request_mask, unsigned int flags)
 {
 	struct inode *inode = d_inode(path->dentry);
-	generic_fillattr(mnt_userns, inode, stat);
-	stat->blksize = MSDOS_SB(inode->i_sb)->cluster_size;
+	struct msdos_sb_info *sbi = MSDOS_SB(inode->i_sb);
 
-	if (MSDOS_SB(inode->i_sb)->options.nfs == FAT_NFS_NOSTALE_RO) {
+	generic_fillattr(mnt_userns, inode, stat);
+	stat->blksize = sbi->cluster_size;
+
+	if (sbi->options.nfs == FAT_NFS_NOSTALE_RO) {
 		/* Use i_pos for ino. This is used as fileid of nfs. */
-		stat->ino = fat_i_pos_read(MSDOS_SB(inode->i_sb), inode);
+		stat->ino = fat_i_pos_read(sbi, inode);
 	}
+
+	if (sbi->options.isvfat && request_mask & STATX_BTIME) {
+		stat->result_mask |= STATX_BTIME;
+		stat->btime = MSDOS_I(inode)->i_crtime;
+	}
+
 	return 0;
 }
 EXPORT_SYMBOL_GPL(fat_getattr);

fs/fat/inode.c

@@ -568,9 +568,11 @@ int fat_fill_inode(struct inode *inode, struct msdos_dir_entry *de)
 
 	fat_time_fat2unix(sbi, &inode->i_mtime, de->time, de->date, 0);
 	inode->i_ctime = inode->i_mtime;
-	if (sbi->options.isvfat)
+	if (sbi->options.isvfat) {
 		fat_time_fat2unix(sbi, &inode->i_atime, 0, de->adate, 0);
-	else
+		fat_time_fat2unix(sbi, &MSDOS_I(inode)->i_crtime, de->ctime,
+				  de->cdate, de->ctime_cs);
+	} else
 		inode->i_atime = fat_truncate_atime(sbi, &inode->i_mtime);
 
 	return 0;
@@ -756,6 +758,8 @@ static struct inode *fat_alloc_inode(struct super_block *sb)
 	ei->i_logstart = 0;
 	ei->i_attrs = 0;
 	ei->i_pos = 0;
+	ei->i_crtime.tv_sec = 0;
+	ei->i_crtime.tv_nsec = 0;
 
 	return &ei->vfs_inode;
 }
@@ -889,6 +893,8 @@ retry:
 		__le16 atime;
 		fat_time_unix2fat(sbi, &inode->i_atime, &atime,
 				  &raw_entry->adate, NULL);
+		fat_time_unix2fat(sbi, &MSDOS_I(inode)->i_crtime, &raw_entry->ctime,
+				  &raw_entry->cdate, &raw_entry->ctime_cs);
 	}
 	spin_unlock(&sbi->inode_hash_lock);
 	mark_buffer_dirty(bh);