exfat: truncate atimes to 2s granularity

The timestamp for access_time has double seconds granularity(There is no
10msIncrement field for access_time unlike create/modify_time).
exfat's atimes are restricted to only 2s granularity so after
we set an atime, round it down to the nearest 2s and set the
sub-second component of the timestamp to 0.
Signed-off-by: Eric Sandeen <sandeen@sandeen.net>
Signed-off-by: Namjae Jeon <namjae.jeon@samsung.com>

fs/exfat/exfat_fs.h

@@ -507,6 +507,7 @@ void exfat_msg(struct super_block *sb, const char *lv, const char *fmt, ...)
 		__printf(3, 4) __cold;
 void exfat_get_entry_time(struct exfat_sb_info *sbi, struct timespec64 *ts,
 		u8 tz, __le16 time, __le16 date, u8 time_ms);
+void exfat_truncate_atime(struct timespec64 *ts);
 void exfat_set_entry_time(struct exfat_sb_info *sbi, struct timespec64 *ts,
 		u8 *tz, __le16 *time, __le16 *date, u8 *time_ms);
 unsigned short exfat_calc_chksum_2byte(void *data, int len,

fs/exfat/file.c

@@ -273,6 +273,7 @@ int exfat_getattr(const struct path *path, struct kstat *stat,
 	struct exfat_inode_info *ei = EXFAT_I(inode);
 
 	generic_fillattr(inode, stat);
+	exfat_truncate_atime(&stat->atime);
 	stat->result_mask |= STATX_BTIME;
 	stat->btime.tv_sec = ei->i_crtime.tv_sec;
 	stat->btime.tv_nsec = ei->i_crtime.tv_nsec;
@@ -339,6 +340,7 @@ int exfat_setattr(struct dentry *dentry, struct iattr *attr)
 	}
 
 	setattr_copy(inode, attr);
+	exfat_truncate_atime(&inode->i_atime);
 	mark_inode_dirty(inode);
 
 out:

fs/exfat/misc.c

@@ -88,7 +88,8 @@ void exfat_get_entry_time(struct exfat_sb_info *sbi, struct timespec64 *ts,
 	if (time_ms) {
 		ts->tv_sec += time_ms / 100;
 		ts->tv_nsec = (time_ms % 100) * 10 * NSEC_PER_MSEC;
-	}
+	} else
+		ts->tv_nsec = 0;
 
 	if (tz & EXFAT_TZ_VALID)
 		/* Adjust timezone to UTC0. */
@@ -124,6 +125,17 @@ void exfat_set_entry_time(struct exfat_sb_info *sbi, struct timespec64 *ts,
 	*tz = EXFAT_TZ_VALID;
 }
 
+/*
+ * The timestamp for access_time has double seconds granularity.
+ * (There is no 10msIncrement field for access_time unlike create/modify_time)
+ * atime also has only a 2-second resolution.
+ */
+void exfat_truncate_atime(struct timespec64 *ts)
+{
+	ts->tv_sec = round_down(ts->tv_sec, 2);
+	ts->tv_nsec = 0;
+}
+
 unsigned short exfat_calc_chksum_2byte(void *data, int len,
 		unsigned short chksum, int type)
 {

fs/exfat/namei.c

@@ -595,6 +595,7 @@ static int exfat_create(struct inode *dir, struct dentry *dentry, umode_t mode,
 	inode_inc_iversion(inode);
 	inode->i_mtime = inode->i_atime = inode->i_ctime =
 		EXFAT_I(inode)->i_crtime = current_time(inode);
+	exfat_truncate_atime(&inode->i_atime);
 	/* timestamp is already written, so mark_inode_dirty() is unneeded. */
 
 	d_instantiate(dentry, inode);
@@ -854,6 +855,7 @@ static int exfat_unlink(struct inode *dir, struct dentry *dentry)
 
 	inode_inc_iversion(dir);
 	dir->i_mtime = dir->i_atime = current_time(dir);
+	exfat_truncate_atime(&dir->i_atime);
 	if (IS_DIRSYNC(dir))
 		exfat_sync_inode(dir);
 	else
@@ -861,6 +863,7 @@ static int exfat_unlink(struct inode *dir, struct dentry *dentry)
 
 	clear_nlink(inode);
 	inode->i_mtime = inode->i_atime = current_time(inode);
+	exfat_truncate_atime(&inode->i_atime);
 	exfat_unhash_inode(inode);
 	exfat_d_version_set(dentry, inode_query_iversion(dir));
 unlock:
@@ -903,6 +906,7 @@ static int exfat_mkdir(struct inode *dir, struct dentry *dentry, umode_t mode)
 	inode_inc_iversion(inode);
 	inode->i_mtime = inode->i_atime = inode->i_ctime =
 		EXFAT_I(inode)->i_crtime = current_time(inode);
+	exfat_truncate_atime(&inode->i_atime);
 	/* timestamp is already written, so mark_inode_dirty() is unneeded. */
 
 	d_instantiate(dentry, inode);
@@ -1019,6 +1023,7 @@ static int exfat_rmdir(struct inode *dir, struct dentry *dentry)
 
 	inode_inc_iversion(dir);
 	dir->i_mtime = dir->i_atime = current_time(dir);
+	exfat_truncate_atime(&dir->i_atime);
 	if (IS_DIRSYNC(dir))
 		exfat_sync_inode(dir);
 	else
@@ -1027,6 +1032,7 @@ static int exfat_rmdir(struct inode *dir, struct dentry *dentry)
 
 	clear_nlink(inode);
 	inode->i_mtime = inode->i_atime = current_time(inode);
+	exfat_truncate_atime(&inode->i_atime);
 	exfat_unhash_inode(inode);
 	exfat_d_version_set(dentry, inode_query_iversion(dir));
 unlock:
@@ -1387,6 +1393,7 @@ static int exfat_rename(struct inode *old_dir, struct dentry *old_dentry,
 	inode_inc_iversion(new_dir);
 	new_dir->i_ctime = new_dir->i_mtime = new_dir->i_atime =
 		EXFAT_I(new_dir)->i_crtime = current_time(new_dir);
+	exfat_truncate_atime(&new_dir->i_atime);
 	if (IS_DIRSYNC(new_dir))
 		exfat_sync_inode(new_dir);
 	else

fs/exfat/super.c

@@ -342,6 +342,7 @@ static int exfat_read_root(struct inode *inode)
 	exfat_save_attr(inode, ATTR_SUBDIR);
 	inode->i_mtime = inode->i_atime = inode->i_ctime = ei->i_crtime =
 		current_time(inode);
+	exfat_truncate_atime(&inode->i_atime);
 	exfat_cache_init_inode(inode);
 	return 0;
 }