[PATCH v4 3/3] fat: report creation time in statx

[Chung-Chiang Cheng <cccheng@synology.com>]

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

The unused code in fat_truncate_crtime() is also removed because only
vfat support creation time.

Signed-off-by: Chung-Chiang Cheng <cccheng@synology.com>
---
 fs/fat/fat.h        |  1 +
 fs/fat/file.c       | 14 +++++++++++---
 fs/fat/inode.c      | 10 ++++++++--
 fs/fat/misc.c       |  3 +--
 fs/fat/namei_vfat.c |  1 +
 5 files changed, 22 insertions(+), 7 deletions(-)

diff --git a/fs/fat/fat.h b/fs/fat/fat.h
index 508b4f2a1ffb..e4409ee82ea9 100644
--- a/fs/fat/fat.h
+++ b/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;
 };
 
diff --git a/fs/fat/file.c b/fs/fat/file.c
index a5a309fcc7fa..8f5218450a3a 100644
--- a/fs/fat/file.c
+++ b/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);
+	struct msdos_sb_info *sbi = MSDOS_SB(inode->i_sb);
+
 	generic_fillattr(mnt_userns, inode, stat);
-	stat->blksize = MSDOS_SB(inode->i_sb)->cluster_size;
+	stat->blksize = sbi->cluster_size;
 
-	if (MSDOS_SB(inode->i_sb)->options.nfs == FAT_NFS_NOSTALE_RO) {
+	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);
diff --git a/fs/fat/inode.c b/fs/fat/inode.c
index f2ac55cd4ea4..ebc124f44e86 100644
--- a/fs/fat/inode.c
+++ b/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
 		fat_truncate_atime(sbi, &inode->i_mtime, &inode->i_atime);
 
 	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;
 }
@@ -887,6 +891,8 @@ static int __fat_write_inode(struct inode *inode, int wait)
 			  &raw_entry->date, NULL);
 	if (sbi->options.isvfat) {
 		__le16 atime;
+		fat_time_unix2fat(sbi, &MSDOS_I(inode)->i_crtime, &raw_entry->ctime,
+				  &raw_entry->cdate, &raw_entry->ctime_cs);
 		fat_time_unix2fat(sbi, &inode->i_atime, &atime,
 				  &raw_entry->adate, NULL);
 	}
diff --git a/fs/fat/misc.c b/fs/fat/misc.c
index ef09b6361602..dfc5d6df3519 100644
--- a/fs/fat/misc.c
+++ b/fs/fat/misc.c
@@ -309,9 +309,8 @@ void fat_truncate_crtime(struct msdos_sb_info *sbi, struct timespec64 *ts,
 {
 	if (sbi->options.isvfat)
 		*crtime = fat_timespec64_trunc_10ms(*ts);
-	else
-		*crtime = fat_timespec64_trunc_2secs(*ts);
 }
+EXPORT_SYMBOL_GPL(fat_truncate_crtime);
 
 /*
  * truncate mtime to 2 second granularity
diff --git a/fs/fat/namei_vfat.c b/fs/fat/namei_vfat.c
index 5369d82e0bfb..9187979fed5d 100644
--- a/fs/fat/namei_vfat.c
+++ b/fs/fat/namei_vfat.c
@@ -781,6 +781,7 @@ static int vfat_create(struct user_namespace *mnt_userns, struct inode *dir,
 	}
 	inode_inc_iversion(inode);
 	fat_truncate_time(inode, &ts, S_ATIME|S_CTIME|S_MTIME);
+	fat_truncate_crtime(MSDOS_SB(sb), &MSDOS_I(inode)->i_crtime, &MSDOS_I(inode)->i_crtime);
 	/* timestamp is already written, so mark_inode_dirty() is unneeded. */
 
 	d_instantiate(dentry, inode);
-- 
2.34.1