Problem

Plan

1.Plan for VFS

Milestone	# of patches	Status	Targeted Kernel release
Infrastructure patches for vfs_time and granularity fields 1.4.1 and 1.4.2	2	Done	4.7- rc1
Test time ranges beyond y2038 support, in memory timestamps match with on disk -1.3.1 and 1.3.2	Xfs tests	In progress	5/28/16
Replace CURRENT_TIME and CURRENT_TIME_SEC – 1.2.1	~60	In Progress, waiting for 4.7 rc1 and repost previous.	4.8
Vfs_time patches – 1.4.3	~40	In Progress, waiting for 4.7-rc1	4.8
Fill in right granularities and ranges for FS – 1.2.2 and 1.2.3	~40	Yet to start	4.8
Expose FS granularities and ranges – 1.4.5 and 1.4.6	~5	Yet to start	4.8
Tests to check the granularities and ranges – 1.3.3 and 1.3.4	Xfs tests	Yet to start	6/10/16
Add policy for wrong granularities - 1.4.7	RFC for 4.9	Yet to start
Stat and utime changes – 1.4.8	RFC for 4.9	Yet to start
Tests for I_DIRTY_* flags and mount options -1.3.5 and 1.3.6	Xfs tests	Yet to start	6/30/16
Transition vfs to 64 bit – 1.4.4	2	Ready, wait for other patches to merge	4.10

1.2 Cleanup

There are many clean up tasks that must precede the transitioning of VFS to use 64 bit timestamps. These help streamline the main series.

1.2.1 Replace current_time and current_time_sec

This patch series is aimed at getting rid of CURRENT_TIME and CURRENT_TIME_SEC macros. The macros: CURRENT_TIME and CURRENT_TIME_SEC are primarily used for filesystem timestamps. to the granularity as required by the filesystem. There will also be another series to add range checks and clamping to filesystem time functions that are meant to substitute the above macros:

          struct timespec current_fs_time(struct super_block *sb)

          struct timespec current_fs_time_sec(struct super_block *sb)

These time functions will also be transitioned along with VFS to use struct timespec64 instead of struct timespec. Any use of these macros outside of filesystem timestamps will be replaced by ktime_get*/ get_seconds functions.

Links to posted patches:

http://thread.gmane.org/gmane.linux.file-systems/106912 (Infrastructure patch)
https://lkml.org/lkml/2016/2/3/34
https://lkml.org/lkml/2016/2/22/506

1.2.2 Fill in right granularities

The series is aimed at filling in right granularities in the s_time_gran field of struct super_block. The filed is used to determine the right granularity for nanosecond portion of inode timestamps. Some filesystems, for instance FAT do not initialize granularity fields since they only care about the seconds portion of the timestamps. This will lead to inconsistencies in the in memory timestamps compared to on disk ones as the filesystem uses VFS generic_update_time() which does not clear nanosecond field before updating the inode timestamps. Similar patches need to be submitted for other filesystems with similar issues.

1.2.3 Fill in right ranges

The time ranges supported by filesystems vary according to their on disk formats. The in memory version of the inode timestamps need to match the on disk version. The plan is for VFS to truncate filesystem timestamps according to their limits. Links posted:

http://www.spinics.net/lists/linux-fsdevel/msg96564.html (Infrastructure patch)[http://www.spinics.net/lists/linux-fsdevel/msg96564.html ]

1.3 Test

1.3.1 Test time written on disk and in memory are same

1.3.2 Test time ranges beyond y2038

1.3.3 Test time granularities are what the fs needs

1.3.4 Test time ranges supported are same as what fs reports

1.3.5 Perf tests

1.3.6 Test to check i_dirty_* flags are updating correctly

1.3.7 Test to check with different mount options like lazy atime etc.

1.4 Kernel tasks to transition vfs to use 64 bit times

1.4.1 Infrastructure patches for vfs_time approach

1.4.3 Change each fs to use vfs time patches

1.4.4 Change vfs to use timespec64

1.4.5 Expose fs granularities

1.4.6 Expose fs ranges

1.4.7 Add vfs policy for handling wrong ranges and granularity

1.4.8 Stat and utime api changes

1.5 Runtime library

1.5.1 Make changes in one library

1.5.2 Make it part of some userspace and run it

Overview of file systems

Each file system stores its file modification times in its own format on disk, and a lot of them have the same problem.

file system	time type	expiration year
9p (9P2000)	unsigned 32-bit seconds	2106
file system	time type	expiration year
9p (9P2000)	unsigned 32-bit seconds	2106
9p (9P2000.L)	signed 64-bit seconds, ns	never
adfs	40-bit cs since 1900	2248
affs	u32 days/mins/(secs/50)	11760870
afs	unsigned 32-bit seconds	2106
befs	unsigned 48-bit seconds	never
bfs	unsigned 32-bit seconds	2106
btrfs	signed 64-bit seconds, 32-bit ns	never
ceph	unsigned 32-bit second/ns	2106
cifs (smb)	7-bit years since 1980	2107
cifs (modern)	64-bit 100ns since 1601	30328
coda	timespec ioctl	2038
cramfs	fixed	1970
efs	unsigned 32-bit seconds	2106
exofs	signed 32-bit seconds	2038
ext2	signed 32-bit seconds	2038
ext3	signed 32-bit seconds	2038
ext4 (good old inodes)	signed 32-bit seconds	2038
ext4 (new inodes	34 bit seconds / 30-bit ns	2582
f2fs	64-bit seconds / 32-bit ns	never
fat	7-bit years since 1980, 2s resolution	2107
freevxfs	unsigned 32-bit seconds/u32 microseconds	2106
fuse	64-bit second/32-bit ns	never
gfs2	u64 seconds/u32 ns	never
hfs	u32 seconds since 1904	2040
hfsplus	u32 seconds since 1904	2040
hostfs	timespec	2038
hpfs	unsigned 32-bit seconds	2106
isofs	'char' year since 1900 (fixable)	2028
jffs2	unsigned 32-bit seconds	2106
jfs	unsigned 32-bit seconds/ns	2106
logfs	signed 64-bit ns	2262
minix	unsigned 32-bit seconds	2106
ncpfs	7-bit year since 1980	2107
nfsv2,v3	unsigned 32-bit seconds/ns	2106
nfsv4	u64 seconds/u32 ns	never
nfsd	unsigned 32-bit seconds/ns	2106
nilfs2	u64 seconds/u32 ns	never
ntfs	64-bit 100ns since 1601	30828
ocfs2	34-bit seconds/30-bit ns	2514
omfs	64-bit milliseconds	never
pstore	ascii seconds	2106
qnx4	unsigned 32-bit seconds	2106
qnx6	unsigned 32-bit seconds	2106
reiserfs	unsigned 32-bit seconds	2106
romfs	fixed	1970
squashfs	unsigned 32-bit seconds	2106
sysv	unsigned 32-bit seconds	2106
ubifs	u64 second/u32 ns	never
udf	u16 year	2038
ufs1	signed 32-bit seconds	2038
ufs2	signed 64-bit seconds/u32 ns	never
xfs	signed 32-bit seconds/ns	2106