[PATCH v3 1/3] fat: split fat_truncate_time() into separate functions

[PATCH v3 1/3] fat: split fat_truncate_time() into separate functions

[Chung-Chiang Cheng]

Separate fat_truncate_time() to each timestamps for later creation time
work.

This patch does not introduce any functional changes, it's merely
refactoring change.

Signed-off-by: Chung-Chiang Cheng <cccheng@synology.com>
---
 fs/fat/fat.h  |  6 +++++
 fs/fat/misc.c | 72 ++++++++++++++++++++++++++++++++-------------------
 2 files changed, 52 insertions(+), 26 deletions(-)

diff --git a/fs/fat/fat.h b/fs/fat/fat.h
index 02d4d4234956..508b4f2a1ffb 100644
--- a/fs/fat/fat.h
+++ b/fs/fat/fat.h
@@ -446,6 +446,12 @@ extern void fat_time_fat2unix(struct msdos_sb_info *sbi, struct timespec64 *ts,
 			      __le16 __time, __le16 __date, u8 time_cs);
 extern void fat_time_unix2fat(struct msdos_sb_info *sbi, struct timespec64 *ts,
 			      __le16 *time, __le16 *date, u8 *time_cs);
+extern void fat_truncate_atime(struct msdos_sb_info *sbi, struct timespec64 *ts,
+			       struct timespec64 *atime);
+extern void fat_truncate_crtime(struct msdos_sb_info *sbi, struct timespec64 *ts,
+				struct timespec64 *crtime);
+extern void fat_truncate_mtime(struct msdos_sb_info *sbi, struct timespec64 *ts,
+			       struct timespec64 *mtime);
 extern int fat_truncate_time(struct inode *inode, struct timespec64 *now,
 			     int flags);
 extern int fat_update_time(struct inode *inode, struct timespec64 *now,
diff --git a/fs/fat/misc.c b/fs/fat/misc.c
index 91ca3c304211..c87df64f8b2b 100644
--- a/fs/fat/misc.c
+++ b/fs/fat/misc.c
@@ -282,16 +282,49 @@ static inline struct timespec64 fat_timespec64_trunc_10ms(struct timespec64 ts)
 	return ts;
 }
 
+/*
+ * truncate atime to 24 hour granularity (00:00:00 in local timezone)
+ */
+void fat_truncate_atime(struct msdos_sb_info *sbi, struct timespec64 *ts,
+			struct timespec64 *atime)
+{
+	/* to localtime */
+	time64_t seconds = ts->tv_sec - fat_tz_offset(sbi);
+	s32 remainder;
+
+	div_s64_rem(seconds, SECS_PER_DAY, &remainder);
+	/* to day boundary, and back to unix time */
+	seconds = seconds + fat_tz_offset(sbi) - remainder;
+
+	*atime = (struct timespec64){ seconds, 0 };
+}
+
+/*
+ * truncate creation time with appropriate granularity:
+ *   msdos - 2 seconds
+ *   vfat  - 10 milliseconds
+ */
+void fat_truncate_crtime(struct msdos_sb_info *sbi, struct timespec64 *ts,
+			 struct timespec64 *crtime)
+{
+	if (sbi->options.isvfat)
+		*crtime = fat_timespec64_trunc_10ms(*ts);
+	else
+		*crtime = fat_timespec64_trunc_2secs(*ts);
+}
+
+/*
+ * truncate mtime to 2 second granularity
+ */
+void fat_truncate_mtime(struct msdos_sb_info *sbi, struct timespec64 *ts,
+			struct timespec64 *mtime)
+{
+	*mtime = fat_timespec64_trunc_2secs(*ts);
+}
+
 /*
  * truncate the various times with appropriate granularity:
- *   root inode:
- *     all times always 0
- *   all other inodes:
- *     mtime - 2 seconds
- *     ctime
- *       msdos - 2 seconds
- *       vfat  - 10 milliseconds
- *     atime - 24 hours (00:00:00 in local timezone)
+ *   all times in root node are always 0
  */
 int fat_truncate_time(struct inode *inode, struct timespec64 *now, int flags)
 {
@@ -306,25 +339,12 @@ int fat_truncate_time(struct inode *inode, struct timespec64 *now, int flags)
 		ts = current_time(inode);
 	}
 
-	if (flags & S_ATIME) {
-		/* to localtime */
-		time64_t seconds = now->tv_sec - fat_tz_offset(sbi);
-		s32 remainder;
-
-		div_s64_rem(seconds, SECS_PER_DAY, &remainder);
-		/* to day boundary, and back to unix time */
-		seconds = seconds + fat_tz_offset(sbi) - remainder;
-
-		inode->i_atime = (struct timespec64){ seconds, 0 };
-	}
-	if (flags & S_CTIME) {
-		if (sbi->options.isvfat)
-			inode->i_ctime = fat_timespec64_trunc_10ms(*now);
-		else
-			inode->i_ctime = fat_timespec64_trunc_2secs(*now);
-	}
+	if (flags & S_ATIME)
+		fat_truncate_atime(sbi, now, &inode->i_atime);
+	if (flags & S_CTIME)
+		fat_truncate_crtime(sbi, now, &inode->i_ctime);
 	if (flags & S_MTIME)
-		inode->i_mtime = fat_timespec64_trunc_2secs(*now);
+		fat_truncate_mtime(sbi, now, &inode->i_mtime);
 
 	return 0;
 }
-- 
2.34.1

[PATCH v3 2/3] fat: make ctime and mtime identical explicitly

[Chung-Chiang Cheng]

FAT supports creation time but not change time, and there was no
corresponding timestamp for creation time in previous VFS. The
original implementation took the compromise of saving the in-memory
change time into the on-disk creation time field, but this would lead
to compatibility issues with non-linux systems.

To address this issue, this patch changes the behavior of ctime. ctime
will no longer be loaded and stored from the creation time on disk.
Instead of that, it'll be consistent with the in-memory mtime and
share the same on-disk field.

Signed-off-by: Chung-Chiang Cheng <cccheng@synology.com>
---
 fs/fat/dir.c         |  2 +-
 fs/fat/file.c        |  4 ++++
 fs/fat/inode.c       | 11 ++++-------
 fs/fat/misc.c        | 11 ++++++++---
 fs/fat/namei_msdos.c |  6 +++---
 fs/fat/namei_vfat.c  |  6 +++---
 6 files changed, 23 insertions(+), 17 deletions(-)

diff --git a/fs/fat/dir.c b/fs/fat/dir.c
index 249825017da7..0ae0dfe278fb 100644
--- a/fs/fat/dir.c
+++ b/fs/fat/dir.c
@@ -1068,7 +1068,7 @@ int fat_remove_entries(struct inode *dir, struct fat_slot_info *sinfo)
 		}
 	}
 
-	fat_truncate_time(dir, NULL, S_ATIME|S_MTIME);
+	fat_truncate_time(dir, NULL, S_ATIME|S_CTIME|S_MTIME);
 	if (IS_DIRSYNC(dir))
 		(void)fat_sync_inode(dir);
 	else
diff --git a/fs/fat/file.c b/fs/fat/file.c
index a5a309fcc7fa..178c1dde3488 100644
--- a/fs/fat/file.c
+++ b/fs/fat/file.c
@@ -544,6 +544,10 @@ int fat_setattr(struct user_namespace *mnt_userns, struct dentry *dentry,
 	/*
 	 * setattr_copy can't truncate these appropriately, so we'll
 	 * copy them ourselves
+	 *
+	 * fat_truncate_time() keeps ctime and mtime the same. if both
+	 * ctime and mtime are need to update here, mtime will overwrite
+	 * ctime
 	 */
 	if (attr->ia_valid & ATTR_ATIME)
 		fat_truncate_time(inode, &attr->ia_atime, S_ATIME);
diff --git a/fs/fat/inode.c b/fs/fat/inode.c
index bf6051bdf1d1..f2ac55cd4ea4 100644
--- a/fs/fat/inode.c
+++ b/fs/fat/inode.c
@@ -567,12 +567,11 @@ int fat_fill_inode(struct inode *inode, struct msdos_dir_entry *de)
 			   & ~((loff_t)sbi->cluster_size - 1)) >> 9;
 
 	fat_time_fat2unix(sbi, &inode->i_mtime, de->time, de->date, 0);
-	if (sbi->options.isvfat) {
-		fat_time_fat2unix(sbi, &inode->i_ctime, de->ctime,
-				  de->cdate, de->ctime_cs);
+	inode->i_ctime = inode->i_mtime;
+	if (sbi->options.isvfat)
 		fat_time_fat2unix(sbi, &inode->i_atime, 0, de->adate, 0);
-	} else
-		fat_truncate_time(inode, &inode->i_mtime, S_ATIME|S_CTIME);
+	else
+		fat_truncate_atime(sbi, &inode->i_mtime, &inode->i_atime);
 
 	return 0;
 }
@@ -888,8 +887,6 @@ static int __fat_write_inode(struct inode *inode, int wait)
 			  &raw_entry->date, NULL);
 	if (sbi->options.isvfat) {
 		__le16 atime;
-		fat_time_unix2fat(sbi, &inode->i_ctime, &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 c87df64f8b2b..71e6dadf12a2 100644
--- a/fs/fat/misc.c
+++ b/fs/fat/misc.c
@@ -341,10 +341,15 @@ int fat_truncate_time(struct inode *inode, struct timespec64 *now, int flags)
 
 	if (flags & S_ATIME)
 		fat_truncate_atime(sbi, now, &inode->i_atime);
-	if (flags & S_CTIME)
-		fat_truncate_crtime(sbi, now, &inode->i_ctime);
-	if (flags & S_MTIME)
+
+	/*
+	 * ctime and mtime share the same on-disk field, and should be
+	 * identical in memory.
+	 */
+	if (flags & (S_CTIME|S_MTIME)) {
 		fat_truncate_mtime(sbi, now, &inode->i_mtime);
+		inode->i_ctime = inode->i_mtime;
+	}
 
 	return 0;
 }
diff --git a/fs/fat/namei_msdos.c b/fs/fat/namei_msdos.c
index efba301d68ae..b2760a716707 100644
--- a/fs/fat/namei_msdos.c
+++ b/fs/fat/namei_msdos.c
@@ -328,7 +328,7 @@ static int msdos_rmdir(struct inode *dir, struct dentry *dentry)
 	drop_nlink(dir);
 
 	clear_nlink(inode);
-	fat_truncate_time(inode, NULL, S_CTIME);
+	fat_truncate_time(inode, NULL, S_CTIME|S_MTIME);
 	fat_detach(inode);
 out:
 	mutex_unlock(&MSDOS_SB(sb)->s_lock);
@@ -415,7 +415,7 @@ static int msdos_unlink(struct inode *dir, struct dentry *dentry)
 	if (err)
 		goto out;
 	clear_nlink(inode);
-	fat_truncate_time(inode, NULL, S_CTIME);
+	fat_truncate_time(inode, NULL, S_CTIME|S_MTIME);
 	fat_detach(inode);
 out:
 	mutex_unlock(&MSDOS_SB(sb)->s_lock);
@@ -550,7 +550,7 @@ static int do_msdos_rename(struct inode *old_dir, unsigned char *old_name,
 		drop_nlink(new_inode);
 		if (is_dir)
 			drop_nlink(new_inode);
-		fat_truncate_time(new_inode, &ts, S_CTIME);
+		fat_truncate_time(new_inode, &ts, S_CTIME|S_MTIME);
 	}
 out:
 	brelse(sinfo.bh);
diff --git a/fs/fat/namei_vfat.c b/fs/fat/namei_vfat.c
index 5369d82e0bfb..b8deb859b2b5 100644
--- a/fs/fat/namei_vfat.c
+++ b/fs/fat/namei_vfat.c
@@ -811,7 +811,7 @@ static int vfat_rmdir(struct inode *dir, struct dentry *dentry)
 	drop_nlink(dir);
 
 	clear_nlink(inode);
-	fat_truncate_time(inode, NULL, S_ATIME|S_MTIME);
+	fat_truncate_time(inode, NULL, S_ATIME|S_CTIME|S_MTIME);
 	fat_detach(inode);
 	vfat_d_version_set(dentry, inode_query_iversion(dir));
 out:
@@ -837,7 +837,7 @@ static int vfat_unlink(struct inode *dir, struct dentry *dentry)
 	if (err)
 		goto out;
 	clear_nlink(inode);
-	fat_truncate_time(inode, NULL, S_ATIME|S_MTIME);
+	fat_truncate_time(inode, NULL, S_ATIME|S_CTIME|S_MTIME);
 	fat_detach(inode);
 	vfat_d_version_set(dentry, inode_query_iversion(dir));
 out:
@@ -981,7 +981,7 @@ static int vfat_rename(struct user_namespace *mnt_userns, struct inode *old_dir,
 		drop_nlink(new_inode);
 		if (is_dir)
 			drop_nlink(new_inode);
-		fat_truncate_time(new_inode, &ts, S_CTIME);
+		fat_truncate_time(new_inode, &ts, S_CTIME|S_MTIME);
 	}
 out:
 	brelse(sinfo.bh);
-- 
2.34.1

Re: [PATCH v3 2/3] fat: make ctime and mtime identical explicitly

[OGAWA Hirofumi]

Chung-Chiang Cheng <cccheng@synology.com> writes:

> -	fat_truncate_time(dir, NULL, S_ATIME|S_MTIME);
> +	fat_truncate_time(dir, NULL, S_ATIME|S_CTIME|S_MTIME);

fat_truncate_time() updates i_ctime too. So S_CTIME should not be
necessary here. And I think this is better to use only S_MTIME to tell
this is the point of mtime update.

(And, in fat_truncate_time(), I think S_CTIME is not required, because
we ignore ctime change, isn't it?)

Or you are going to update mtime on rename, etc too?

> +	/*
> +	 * ctime and mtime share the same on-disk field, and should be
> +	 * identical in memory.
> +	 */
> +	if (flags & (S_CTIME|S_MTIME)) {
>  		fat_truncate_mtime(sbi, now, &inode->i_mtime);
> +		inode->i_ctime = inode->i_mtime;
> +	}

[...]

>  	clear_nlink(inode);
> -	fat_truncate_time(inode, NULL, S_CTIME);
> +	fat_truncate_time(inode, NULL, S_CTIME|S_MTIME);

This is the point to update ctime. You want to affect ctime change to
mtime? As I said in previous post, I think we are better to ignore ctime
change, because it may become yet another incompatible behavior.

>  	fat_detach(inode);
>  out:
>  	mutex_unlock(&MSDOS_SB(sb)->s_lock);
> @@ -415,7 +415,7 @@ static int msdos_unlink(struct inode *dir, struct dentry *dentry)
>  	if (err)
>  		goto out;
>  	clear_nlink(inode);
> -	fat_truncate_time(inode, NULL, S_CTIME);
> +	fat_truncate_time(inode, NULL, S_CTIME|S_MTIME);

ditto

>  	fat_detach(inode);
>  out:
>  	mutex_unlock(&MSDOS_SB(sb)->s_lock);
> @@ -550,7 +550,7 @@ static int do_msdos_rename(struct inode *old_dir, unsigned char *old_name,
>  		drop_nlink(new_inode);
>  		if (is_dir)
>  			drop_nlink(new_inode);
> -		fat_truncate_time(new_inode, &ts, S_CTIME);
> +		fat_truncate_time(new_inode, &ts, S_CTIME|S_MTIME);

ditto

>  	}
>  out:

[...]

> @@ -981,7 +981,7 @@ static int vfat_rename(struct user_namespace *mnt_userns, struct inode *old_dir,
>  		drop_nlink(new_inode);
>  		if (is_dir)
>  			drop_nlink(new_inode);
> -		fat_truncate_time(new_inode, &ts, S_CTIME);
> +		fat_truncate_time(new_inode, &ts, S_CTIME|S_MTIME);

ditto

Thanks.
-- 
OGAWA Hirofumi <hirofumi@mail.parknet.co.jp>

Re: [PATCH v3 2/3] fat: make ctime and mtime identical explicitly

[Chung-Chiang Cheng]

On Fri, Apr 15, 2022 at 9:28 PM OGAWA Hirofumi
<hirofumi@mail.parknet.co.jp> wrote:
>
> Chung-Chiang Cheng <cccheng@synology.com> writes:
>
> > -     fat_truncate_time(dir, NULL, S_ATIME|S_MTIME);
> > +     fat_truncate_time(dir, NULL, S_ATIME|S_CTIME|S_MTIME);
>
> fat_truncate_time() updates i_ctime too. So S_CTIME should not be
> necessary here. And I think this is better to use only S_MTIME to tell
> this is the point of mtime update.
>
> (And, in fat_truncate_time(), I think S_CTIME is not required, because
> we ignore ctime change, isn't it?)
>
> >       clear_nlink(inode);
> > -     fat_truncate_time(inode, NULL, S_CTIME);
> > +     fat_truncate_time(inode, NULL, S_CTIME|S_MTIME);
>
> This is the point to update ctime. You want to affect ctime change to
> mtime? As I said in previous post, I think we are better to ignore ctime
> change, because it may become yet another incompatible behavior.
>

Thanks for the feedback. I will change the behavior to ignore ctime
updates in the next version of the patch.

[PATCH v3 3/3] fat: report creation time in statx

[Chung-Chiang Cheng]

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

Signed-off-by: Chung-Chiang Cheng <cccheng@synology.com>
---
 fs/fat/fat.h   |  1 +
 fs/fat/file.c  | 14 +++++++++++---
 fs/fat/inode.c | 12 ++++++++++--
 3 files changed, 22 insertions(+), 5 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 178c1dde3488..7a4f617d4928 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..23fac3181fa7 100644
--- a/fs/fat/inode.c
+++ b/fs/fat/inode.c
@@ -568,10 +568,14 @@ 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);
+		fat_truncate_crtime(sbi, &inode->i_mtime, &MSDOS_I(inode)->i_crtime);
+	}
 
 	return 0;
 }
@@ -756,6 +760,8 @@ 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 +893,8 @@ 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);
 	}
-- 
2.34.1

Re: [PATCH v3 3/3] fat: report creation time in statx

[OGAWA Hirofumi]

Chung-Chiang Cheng <cccheng@synology.com> writes:

> @@ -568,10 +568,14 @@ 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);
> +		fat_truncate_crtime(sbi, &inode->i_mtime, &MSDOS_I(inode)->i_crtime);
> +	}

Probably, nothing worth to update i_crtime here, right?

Thanks.
-- 
OGAWA Hirofumi <hirofumi@mail.parknet.co.jp>

Re: [PATCH v3 3/3] fat: report creation time in statx

[Chung-Chiang Cheng]

> > +     } else {
> >               fat_truncate_atime(sbi, &inode->i_mtime, &inode->i_atime);
> > +             fat_truncate_crtime(sbi, &inode->i_mtime, &MSDOS_I(inode)->i_crtime);
> > +     }
>
> Probably, nothing worth to update i_crtime here, right?
>

That's right. I also miss truncating the create-time for newly created
files in vfat. I will add it back in the next patch. It will be the only
location that calls fat_truncate_crtime().

@@ -781,11 +782,12 @@ 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(...)


I also have a question. If msdos doesn't support create-time, why does the
original fat_truncate_time() truncate it to a 2-sec granularity?

if (flags & S_CTIME) {
        if (sbi->options.isvfat)
                inode->i_ctime = fat_timespec64_trunc_10ms(*now);
        else
                inode->i_ctime = fat_timespec64_trunc_2secs(*now);
}

This logic was introduced in 6bb885ecd746 (fat: add functions to update
and truncate timestamps appropriately"), and seems not for change-time.
Should I remove it?

Thanks.

Re: [PATCH v3 3/3] fat: report creation time in statx

[OGAWA Hirofumi]

Chung-Chiang Cheng <shepjeng@gmail.com> writes:

>
> I also have a question. If msdos doesn't support create-time, why does the
> original fat_truncate_time() truncate it to a 2-sec granularity?
>
> if (flags & S_CTIME) {
>         if (sbi->options.isvfat)
>                 inode->i_ctime = fat_timespec64_trunc_10ms(*now);
>         else
>                 inode->i_ctime = fat_timespec64_trunc_2secs(*now);
> }
>
> This logic was introduced in 6bb885ecd746 (fat: add functions to update
> and truncate timestamps appropriately"), and seems not for change-time.
> Should I remove it?

Hm, not sure.

However, ctime/atime is not stored into backing storage in
__fat_write_inode() and loaded if !isvfat (if I'm not missing
something).  So I think we don't need it for creation time.

Thanks.
-- 
OGAWA Hirofumi <hirofumi@mail.parknet.co.jp>