[PATCH v2 00/24] Delete CURRENT_TIME and CURRENT_TIME_SEC macros

[PATCH v2 00/24] Delete CURRENT_TIME and CURRENT_TIME_SEC macros

[Deepa Dinamani]

The series is aimed at getting rid of CURRENT_TIME and CURRENT_TIME_SEC macros.
The macros are not y2038 safe. There is no plan to transition them into being
y2038 safe.
ktime_get_* api's can be used in their place. And, these are y2038 safe.

Thanks to Arnd Bergmann for all the guidance and discussions.

Patches 2-4 were mostly generated using coccinelle scripts.

All filesystem timestamps use current_fs_time() for right granularity as
mentioned in the respective commit texts of patches. This has a changed
signature, renamed to current_time() and moved to the fs/inode.c.

This series also serves as a preparatory series to transition vfs to 64 bit
timestamps as outlined here: https://lkml.org/lkml/2016/2/12/104 .

As per Linus's suggestion in https://lkml.org/lkml/2016/5/24/663 , all the
inode timestamp changes have been squashed into a single patch. Also,
current_time() now is used as a single generic vfs filesystem timestamp api.
It also takes struct inode* as argument instead of struct super_block*.
Posting all patches together in a bigger series so that the big picture is
clear.

As per the suggestion in https://lwn.net/Articles/672598/, CURRENT_TIME macro
bug fixes are being handled in a series separate from transitioning vfs to use.

Changes from v1:
* Change current_fs_time(struct super_block *) to current_time(struct inode *)

* Note that change to add time64_to_tm() is already part of John's
  kernel tree: https://lkml.org/lkml/2016/6/17/875 .

Deepa Dinamani (24):
  vfs: Add current_time() api
  fs: Replace CURRENT_TIME with current_time() for inode timestamps
  fs: Replace CURRENT_TIME_SEC with current_time() for inode timestamps
  fs: Replace current_fs_time() with current_time()
  fs: jfs: Replace CURRENT_TIME_SEC by current_time()
  fs: ext4: Use current_time() for inode timestamps
  fs: ubifs: Replace CURRENT_TIME_SEC with current_time
  fs: btrfs: Use ktime_get_real_ts for root ctime
  fs: udf: Replace CURRENT_TIME with current_time()
  fs: cifs: Replace CURRENT_TIME by current_time()
  fs: cifs: Replace CURRENT_TIME with ktime_get_real_ts()
  fs: cifs: Replace CURRENT_TIME by get_seconds
  fs: f2fs: Use ktime_get_real_seconds for sit_info times
  drivers: staging: lustre: Replace CURRENT_TIME with current_time()
  fs: ocfs2: Use time64_t to represent orphan scan times
  fs: ocfs2: Replace CURRENT_TIME with ktime_get_real_seconds()
  audit: Use timespec64 to represent audit timestamps
  fs: nfs: Make nfs boot time y2038 safe
  fnic: Use time64_t to represent trace timestamps
  block: Replace CURRENT_TIME with ktime_get_real_ts
  libceph: Replace CURRENT_TIME with ktime_get_real_ts
  fs: ceph: Replace current_fs_time for request stamp
  time: Delete CURRENT_TIME_SEC and CURRENT_TIME macro
  time: Delete current_fs_time() function

 arch/powerpc/platforms/cell/spufs/inode.c          |  2 +-
 arch/s390/hypfs/inode.c                            |  4 ++--
 drivers/block/rbd.c                                |  2 +-
 drivers/char/sonypi.c                              |  2 +-
 drivers/infiniband/hw/qib/qib_fs.c                 |  2 +-
 drivers/misc/ibmasm/ibmasmfs.c                     |  2 +-
 drivers/oprofile/oprofilefs.c                      |  2 +-
 drivers/platform/x86/sony-laptop.c                 |  2 +-
 drivers/scsi/fnic/fnic_trace.c                     |  4 ++--
 drivers/scsi/fnic/fnic_trace.h                     |  2 +-
 drivers/staging/lustre/lustre/llite/llite_lib.c    | 16 ++++++-------
 drivers/staging/lustre/lustre/llite/namei.c        |  4 ++--
 drivers/staging/lustre/lustre/mdc/mdc_reint.c      |  6 ++---
 .../lustre/lustre/obdclass/linux/linux-obdo.c      |  6 ++---
 drivers/staging/lustre/lustre/obdclass/obdo.c      |  6 ++---
 drivers/staging/lustre/lustre/osc/osc_io.c         |  2 +-
 drivers/usb/core/devio.c                           | 18 +++++++-------
 drivers/usb/gadget/function/f_fs.c                 |  8 +++----
 drivers/usb/gadget/legacy/inode.c                  |  2 +-
 fs/9p/vfs_inode.c                                  |  2 +-
 fs/adfs/inode.c                                    |  2 +-
 fs/affs/amigaffs.c                                 |  6 ++---
 fs/affs/inode.c                                    |  2 +-
 fs/attr.c                                          |  2 +-
 fs/autofs4/inode.c                                 |  2 +-
 fs/autofs4/root.c                                  |  6 ++---
 fs/bad_inode.c                                     |  2 +-
 fs/bfs/dir.c                                       | 14 +++++------
 fs/binfmt_misc.c                                   |  2 +-
 fs/btrfs/file.c                                    |  6 ++---
 fs/btrfs/inode.c                                   | 22 ++++++++---------
 fs/btrfs/ioctl.c                                   |  8 +++----
 fs/btrfs/root-tree.c                               |  3 ++-
 fs/btrfs/transaction.c                             |  4 ++--
 fs/btrfs/xattr.c                                   |  2 +-
 fs/ceph/file.c                                     |  4 ++--
 fs/ceph/inode.c                                    |  2 +-
 fs/ceph/mds_client.c                               |  4 +++-
 fs/ceph/xattr.c                                    |  2 +-
 fs/cifs/cifsencrypt.c                              |  4 +++-
 fs/cifs/cifssmb.c                                  | 10 ++++----
 fs/cifs/file.c                                     |  4 ++--
 fs/cifs/inode.c                                    | 28 ++++++++++++----------
 fs/coda/dir.c                                      |  2 +-
 fs/coda/file.c                                     |  2 +-
 fs/coda/inode.c                                    |  2 +-
 fs/configfs/inode.c                                |  6 ++---
 fs/debugfs/inode.c                                 |  2 +-
 fs/devpts/inode.c                                  |  6 ++---
 fs/efivarfs/inode.c                                |  2 +-
 fs/exofs/dir.c                                     |  6 ++---
 fs/exofs/inode.c                                   |  4 ++--
 fs/exofs/namei.c                                   |  6 ++---
 fs/ext2/acl.c                                      |  2 +-
 fs/ext2/dir.c                                      |  6 ++---
 fs/ext2/ialloc.c                                   |  2 +-
 fs/ext2/inode.c                                    |  4 ++--
 fs/ext2/ioctl.c                                    |  4 ++--
 fs/ext2/namei.c                                    |  6 ++---
 fs/ext2/super.c                                    |  2 +-
 fs/ext2/xattr.c                                    |  2 +-
 fs/ext4/acl.c                                      |  2 +-
 fs/ext4/ext4.h                                     |  6 -----
 fs/ext4/extents.c                                  | 10 ++++----
 fs/ext4/ialloc.c                                   |  2 +-
 fs/ext4/inline.c                                   |  4 ++--
 fs/ext4/inode.c                                    |  6 ++---
 fs/ext4/ioctl.c                                    |  8 +++----
 fs/ext4/namei.c                                    | 24 ++++++++++---------
 fs/ext4/super.c                                    |  2 +-
 fs/ext4/xattr.c                                    |  2 +-
 fs/f2fs/dir.c                                      |  8 +++----
 fs/f2fs/file.c                                     |  8 +++----
 fs/f2fs/inline.c                                   |  2 +-
 fs/f2fs/namei.c                                    | 12 +++++-----
 fs/f2fs/segment.c                                  |  2 +-
 fs/f2fs/segment.h                                  |  5 ++--
 fs/f2fs/xattr.c                                    |  2 +-
 fs/fat/dir.c                                       |  2 +-
 fs/fat/file.c                                      |  6 ++---
 fs/fat/inode.c                                     |  2 +-
 fs/fat/namei_msdos.c                               | 12 +++++-----
 fs/fat/namei_vfat.c                                | 10 ++++----
 fs/fuse/control.c                                  |  2 +-
 fs/fuse/dir.c                                      |  2 +-
 fs/gfs2/bmap.c                                     |  8 +++----
 fs/gfs2/dir.c                                      | 12 +++++-----
 fs/gfs2/inode.c                                    |  8 +++----
 fs/gfs2/quota.c                                    |  2 +-
 fs/gfs2/xattr.c                                    |  8 +++----
 fs/hfs/catalog.c                                   |  8 +++----
 fs/hfs/dir.c                                       |  2 +-
 fs/hfs/inode.c                                     |  2 +-
 fs/hfsplus/catalog.c                               |  8 +++----
 fs/hfsplus/dir.c                                   |  6 ++---
 fs/hfsplus/inode.c                                 |  2 +-
 fs/hfsplus/ioctl.c                                 |  2 +-
 fs/hugetlbfs/inode.c                               | 10 ++++----
 fs/inode.c                                         | 21 +++++++++++++---
 fs/jffs2/acl.c                                     |  2 +-
 fs/jffs2/fs.c                                      |  2 +-
 fs/jfs/acl.c                                       |  2 +-
 fs/jfs/inode.c                                     |  2 +-
 fs/jfs/ioctl.c                                     |  2 +-
 fs/jfs/jfs_inode.c                                 |  2 +-
 fs/jfs/namei.c                                     | 24 +++++++++----------
 fs/jfs/super.c                                     |  2 +-
 fs/jfs/xattr.c                                     |  2 +-
 fs/kernfs/inode.c                                  |  2 +-
 fs/libfs.c                                         | 14 +++++------
 fs/locks.c                                         |  2 +-
 fs/logfs/dir.c                                     |  6 ++---
 fs/logfs/file.c                                    |  2 +-
 fs/logfs/inode.c                                   |  4 ++--
 fs/logfs/readwrite.c                               |  4 ++--
 fs/minix/bitmap.c                                  |  2 +-
 fs/minix/dir.c                                     |  6 ++---
 fs/minix/itree_common.c                            |  4 ++--
 fs/minix/namei.c                                   |  4 ++--
 fs/nfs/client.c                                    |  2 +-
 fs/nfs/netns.h                                     |  2 +-
 fs/nfs/nfs4proc.c                                  | 10 ++++----
 fs/nfs/nfs4xdr.c                                   |  2 +-
 fs/nfsd/blocklayout.c                              |  2 +-
 fs/nilfs2/dir.c                                    |  6 ++---
 fs/nilfs2/inode.c                                  |  4 ++--
 fs/nilfs2/ioctl.c                                  |  2 +-
 fs/nilfs2/namei.c                                  |  6 ++---
 fs/nsfs.c                                          |  2 +-
 fs/ntfs/inode.c                                    |  2 +-
 fs/ntfs/mft.c                                      |  2 +-
 fs/ocfs2/acl.c                                     |  2 +-
 fs/ocfs2/alloc.c                                   |  2 +-
 fs/ocfs2/aops.c                                    |  2 +-
 fs/ocfs2/cluster/heartbeat.c                       |  2 +-
 fs/ocfs2/dir.c                                     |  4 ++--
 fs/ocfs2/dlmfs/dlmfs.c                             |  4 ++--
 fs/ocfs2/file.c                                    | 12 +++++-----
 fs/ocfs2/inode.c                                   |  2 +-
 fs/ocfs2/journal.c                                 |  4 ++--
 fs/ocfs2/move_extents.c                            |  2 +-
 fs/ocfs2/namei.c                                   | 16 +++++++------
 fs/ocfs2/ocfs2.h                                   |  2 +-
 fs/ocfs2/refcounttree.c                            |  4 ++--
 fs/ocfs2/super.c                                   |  2 +-
 fs/ocfs2/xattr.c                                   |  2 +-
 fs/omfs/dir.c                                      |  4 ++--
 fs/omfs/inode.c                                    |  2 +-
 fs/openpromfs/inode.c                              |  2 +-
 fs/orangefs/file.c                                 |  2 +-
 fs/orangefs/inode.c                                |  2 +-
 fs/orangefs/namei.c                                | 10 ++++----
 fs/pipe.c                                          |  2 +-
 fs/posix_acl.c                                     |  2 +-
 fs/proc/base.c                                     |  2 +-
 fs/proc/inode.c                                    |  4 ++--
 fs/proc/proc_sysctl.c                              |  2 +-
 fs/proc/self.c                                     |  2 +-
 fs/proc/thread_self.c                              |  2 +-
 fs/pstore/inode.c                                  |  2 +-
 fs/ramfs/inode.c                                   |  6 ++---
 fs/reiserfs/inode.c                                |  2 +-
 fs/reiserfs/ioctl.c                                |  4 ++--
 fs/reiserfs/namei.c                                | 12 +++++-----
 fs/reiserfs/stree.c                                |  8 +++----
 fs/reiserfs/super.c                                |  2 +-
 fs/reiserfs/xattr.c                                |  6 ++---
 fs/reiserfs/xattr_acl.c                            |  2 +-
 fs/sysv/dir.c                                      |  6 ++---
 fs/sysv/ialloc.c                                   |  2 +-
 fs/sysv/itree.c                                    |  4 ++--
 fs/sysv/namei.c                                    |  4 ++--
 fs/tracefs/inode.c                                 |  2 +-
 fs/ubifs/dir.c                                     | 10 ++++----
 fs/ubifs/file.c                                    | 12 +++++-----
 fs/ubifs/ioctl.c                                   |  2 +-
 fs/ubifs/misc.h                                    | 10 --------
 fs/ubifs/sb.c                                      | 14 +++++++----
 fs/ubifs/xattr.c                                   |  6 ++---
 fs/udf/ialloc.c                                    |  2 +-
 fs/udf/inode.c                                     |  4 ++--
 fs/udf/namei.c                                     | 20 ++++++++--------
 fs/udf/super.c                                     |  9 +++++--
 fs/ufs/dir.c                                       |  6 ++---
 fs/ufs/ialloc.c                                    |  8 ++++---
 fs/ufs/inode.c                                     |  6 ++---
 fs/ufs/namei.c                                     |  6 ++---
 fs/xfs/xfs_acl.c                                   |  2 +-
 fs/xfs/xfs_inode.c                                 |  2 +-
 fs/xfs/xfs_iops.c                                  |  2 +-
 fs/xfs/xfs_trans_inode.c                           |  2 +-
 include/linux/audit.h                              |  4 ++--
 include/linux/fs.h                                 |  2 +-
 include/linux/time.h                               |  3 ---
 ipc/mqueue.c                                       | 18 +++++++-------
 kernel/audit.c                                     | 10 ++++----
 kernel/audit.h                                     |  2 +-
 kernel/auditsc.c                                   |  6 ++---
 kernel/bpf/inode.c                                 |  2 +-
 kernel/time/time.c                                 | 14 -----------
 mm/shmem.c                                         | 20 ++++++++--------
 net/ceph/messenger.c                               |  6 +++--
 net/ceph/osd_client.c                              |  4 ++--
 net/sunrpc/rpc_pipe.c                              |  2 +-
 security/inode.c                                   |  2 +-
 security/selinux/selinuxfs.c                       |  2 +-
 206 files changed, 533 insertions(+), 522 deletions(-)

-- 
1.9.1

Cc: adilger.kernel-m1MBpc4rdrD3fQ9qLvQP4Q@public.gmane.org
Cc: adrian.hunter-ral2JQCrhuEAvxtiuMwx3w@public.gmane.org
Cc: anna.schumaker-HgOvQuBEEgTQT0dZR+AlfA@public.gmane.org
Cc: buchino-FYB4Gu1CFyUAvxtiuMwx3w@public.gmane.org
Cc: ceph-devel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org
Cc: clm-b10kYP2dOMg@public.gmane.org
Cc: cm224.lee-Sze3O3UU22JBDgjK7y7TUQ@public.gmane.org
Cc: dedekind1-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org
Cc: dsterba-IBi9RG/b67k@public.gmane.org
Cc: elder-DgEjT+Ai2ygdnm+yROfE0A@public.gmane.org
Cc: eparis-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org
Cc: gregkh-hQyY1W1yCW8ekmWlsbkhG0B+6BGkLq7r@public.gmane.org
Cc: hiralpat-FYB4Gu1CFyUAvxtiuMwx3w@public.gmane.org
Cc: idryomov-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org
Cc: jack-IBi9RG/b67k@public.gmane.org
Cc: jaegeuk-DgEjT+Ai2ygdnm+yROfE0A@public.gmane.org
Cc: jbacik-b10kYP2dOMg@public.gmane.org
Cc: jejb-23VcF4HTsmIX0ybBhKVfKdBPR1lH4CV8@public.gmane.org
Cc: jfs-discussion-5NWGOfrQmneRv+LV9MX5uipxlwaOVQ5f@public.gmane.org
Cc: jlbec-aKy9MeLSZ9dg9hUCZPvPmw@public.gmane.org
Cc: john.stultz-QSEj5FYQhm4dnm+yROfE0A@public.gmane.org
Cc: linux-audit-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org
Cc: linux-btrfs-u79uwXL29TY76Z2rM5mHXA@public.gmane.org
Cc: linux-ext4-u79uwXL29TY76Z2rM5mHXA@public.gmane.org
Cc: linux-f2fs-devel-5NWGOfrQmneRv+LV9MX5uipxlwaOVQ5f@public.gmane.org
Cc: linux-mtd-IAPFreCvJWM7uuMidbF8XUB+6BGkLq7r@public.gmane.org
Cc: linux-nfs-u79uwXL29TY76Z2rM5mHXA@public.gmane.org
Cc: linux-scsi-u79uwXL29TY76Z2rM5mHXA@public.gmane.org
Cc: lustre-devel-aLEFhgZF4x6X6Mz3xDxJMA@public.gmane.org
Cc: martin.petersen-QHcLZuEGTsvQT0dZR+AlfA@public.gmane.org
Cc: mfasheh-IBi9RG/b67k@public.gmane.org
Cc: ocfs2-devel-N0ozoZBvEnrZJqsBc5GL+g@public.gmane.org
Cc: paul-r2n+y4ga6xFZroRs9YW3xA@public.gmane.org
Cc: sage-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org
Cc: sfrench-eUNUBHrolfbYtjvyW6yDsg@public.gmane.org
Cc: shaggy-DgEjT+Ai2ygdnm+yROfE0A@public.gmane.org
Cc: sramars-FYB4Gu1CFyUAvxtiuMwx3w@public.gmane.org
Cc: trond.myklebust-7I+n7zu2hftEKMMhf/gKZA@public.gmane.org
Cc: zyan-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org

[PATCH v2 13/24] fs: f2fs: Use ktime_get_real_seconds for sit_info times

[Deepa Dinamani]

CURRENT_TIME_SEC is not y2038 safe.

Replace use of CURRENT_TIME_SEC with ktime_get_real_seconds
in segment timestamps used by GC algorithm including the
segment mtime timestamps.

Signed-off-by: Deepa Dinamani <deepa.kernel@gmail.com>
Cc: Jaegeuk Kim <jaegeuk@kernel.org>
Cc: Changman Lee <cm224.lee@samsung.com>
Cc: linux-f2fs-devel@lists.sourceforge.net
---
 fs/f2fs/segment.c | 2 +-
 fs/f2fs/segment.h | 5 +++--
 2 files changed, 4 insertions(+), 3 deletions(-)

diff --git a/fs/f2fs/segment.c b/fs/f2fs/segment.c
index 25b1c47..9c35a21 100644
--- a/fs/f2fs/segment.c
+++ b/fs/f2fs/segment.c
@@ -2156,7 +2156,7 @@ static int build_sit_info(struct f2fs_sb_info *sbi)
 	sit_i->dirty_sentries = 0;
 	sit_i->sents_per_block = SIT_ENTRY_PER_BLOCK;
 	sit_i->elapsed_time = le64_to_cpu(sbi->ckpt->elapsed_time);
-	sit_i->mounted_time = CURRENT_TIME_SEC.tv_sec;
+	sit_i->mounted_time = ktime_get_real_seconds();
 	mutex_init(&sit_i->sentry_lock);
 	return 0;
 }
diff --git a/fs/f2fs/segment.h b/fs/f2fs/segment.h
index d74cc33..78bb034 100644
--- a/fs/f2fs/segment.h
+++ b/fs/f2fs/segment.h
@@ -661,8 +661,9 @@ static inline void set_to_next_sit(struct sit_info *sit_i, unsigned int start)
 static inline unsigned long long get_mtime(struct f2fs_sb_info *sbi)
 {
 	struct sit_info *sit_i = SIT_I(sbi);
-	return sit_i->elapsed_time + CURRENT_TIME_SEC.tv_sec -
-						sit_i->mounted_time;
+	time64_t now = ktime_get_real_seconds();
+
+	return sit_i->elapsed_time + now - sit_i->mounted_time;
 }
 
 static inline void set_summary(struct f2fs_summary *sum, nid_t nid,
-- 
1.9.1

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Re: [PATCH v2 00/24] Delete CURRENT_TIME and CURRENT_TIME_SEC macros

[Linus Torvalds]

On Sun, Jun 19, 2016 at 5:26 PM, Deepa Dinamani <deepa.kernel-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org> wrote:
> The series is aimed at getting rid of CURRENT_TIME and CURRENT_TIME_SEC macros.

This version now looks ok to me.

I do have a comment (or maybe just a RFD) for future work.

It does strike me that once we actually change over the inode times to
use timespec64, the calling conventions are going to be fairly
horrendous on most 32-bit architectures.

Gcc handles 8-byte structure returns (on most architectures) by
returning them as two 32-bit registers (%edx:%eax on x86). But once it
is timespec64, that will no longer be the case, and the calling
convention will end up using a pointer to the local stack instead.

So for 32-bit code generation, we *may* want to introduce a new model of doing

    set_inode_time(inode, ATTR_ATIME | ATTR_MTIME);

which basically just does

    inode->i_atime = inode->i_mtime = current_time(inode);

but with a much easier calling convention on 32-bit architectures.

But that is entirely orthogonal to this patch-set, and should be seen
as a separate issue.

And maybe it doesn't end up helping anyway, but I do think those
"simple" direct assignments will really generate pretty disgusting
code on 32-bit architectures.

That whole

    inode->i_atime = inode->i_mtime = CURRENT_TIME;

model really made a lot more sense back in the ancient days when inode
times were just simply 32-bit seconds (not even timeval structures).

                  Linus

Re: [PATCH v2 00/24] Delete CURRENT_TIME and CURRENT_TIME_SEC macros

[Deepa Dinamani]

> This version now looks ok to me.
>
> I do have a comment (or maybe just a RFD) for future work.
>
> It does strike me that once we actually change over the inode times to
> use timespec64, the calling conventions are going to be fairly
> horrendous on most 32-bit architectures.
>
> Gcc handles 8-byte structure returns (on most architectures) by
> returning them as two 32-bit registers (%edx:%eax on x86). But once it
> is timespec64, that will no longer be the case, and the calling
> convention will end up using a pointer to the local stack instead.
>
> So for 32-bit code generation, we *may* want to introduce a new model of doing
>
>     set_inode_time(inode, ATTR_ATIME | ATTR_MTIME);
>
> which basically just does
>
>     inode->i_atime = inode->i_mtime = current_time(inode);
>
> but with a much easier calling convention on 32-bit architectures.

Arnd and I had discussed something like this before.
But, for entirely different reasons:

Having the set_inode_time() like you suggest will also help switching
of vfs inode times to timespec64.
We were suggesting all the accesses to inode time be abstracted
through something like inode_set_time().
Arnd also had suggested a split representation of fields in the struct
inode as well which led to space savings
as well. And, having the split representation also meant no more
direct assignments:

https://lkml.org/lkml/2016/1/7/20

This in general will be similar to setattr_copy(), but only sets times
rather than other attributes as well.

If this is what is preferred, then the patches to change vfs to use
timespec64 could make use of this and will
need to be refactored. So maybe it would be good to discuss before I
post those patches.

-Deepa

Re: [Y2038] [PATCH v2 00/24] Delete CURRENT_TIME and CURRENT_TIME_SEC macros

[Arnd Bergmann]

On Monday, June 20, 2016 11:03:01 AM CEST you wrote:
> On Sun, Jun 19, 2016 at 5:26 PM, Deepa Dinamani <deepa.kernel-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org> wrote:
> > The series is aimed at getting rid of CURRENT_TIME and CURRENT_TIME_SEC macros.

> Gcc handles 8-byte structure returns (on most architectures) by
> returning them as two 32-bit registers (%edx:%eax on x86). But once it
> is timespec64, that will no longer be the case, and the calling
> convention will end up using a pointer to the local stack instead.

I guess we already have that today, as the implementation of
current_fs_time() is

static inline struct timespec64 tk_xtime(struct timekeeper *tk)
{
        struct timespec64 ts;

        ts.tv_sec = tk->xtime_sec;
        ts.tv_nsec = (long)(tk->tkr_mono.xtime_nsec >> tk->tkr_mono.shift);
        return ts;
}
extern struct timespec64 current_kernel_time64(void);
struct timespec64 current_kernel_time64(void)
{
        struct timekeeper *tk = &tk_core.timekeeper;
        struct timespec64 now;
        unsigned long seq;

        do {
                seq = read_seqcount_begin(&tk_core.seq);

                now = tk_xtime(tk);
        } while (read_seqcount_retry(&tk_core.seq, seq));

        return now;
}
static inline struct timespec current_kernel_time(void)
{
        struct timespec64 now = current_kernel_time64();

        return timespec64_to_timespec(now);
}
extern struct timespec current_fs_time(struct super_block *sb);
struct timespec current_fs_time(struct super_block *sb)
{       
        struct timespec now = current_kernel_time();
        return timespec_trunc(now, sb->s_time_gran);
}       

We can surely do a little better than this, independent of the
conversion in Deepa's patch set.

> So for 32-bit code generation, we *may* want to introduce a new model of doing
> 
>     set_inode_time(inode, ATTR_ATIME | ATTR_MTIME);
> 
> which basically just does
> 
>     inode->i_atime = inode->i_mtime = current_time(inode);
> 
> but with a much easier calling convention on 32-bit architectures.
> 
> But that is entirely orthogonal to this patch-set, and should be seen
> as a separate issue.

I've played around with that, but found it hard to avoid going
through memory other than going all the way to the tk_xtime()
access to copy both tk->xtime_sec and the nanoseconds into
the inode fields.

Without that, the set_inode_time() implementation ends up
being more expensive than
inode->i_atime = inode->i_ctime = inode->i_mtime = current_time(inode);
because we still copy through the stack but also have
a couple of conditional branches that we don't have at the
moment.

At the moment, the triple assignment becomes (here on ARM)

   c:   4668            mov     r0, sp
  12:   f7ff fffe       bl      0 <current_kernel_time64>
  3e:   f107 0520       add.w   r5, r7, #32
                        12: R_ARM_THM_CALL      current_kernel_time64
  16:   f106 0410       add.w   r4, r6, #16
  1a:   e89d 000f       ldmia.w sp, {r0, r1, r2, r3} # load from stack
  1e:   e885 000f       stmia.w r5, {r0, r1, r2, r3} # store into i_atime
  22:   e884 000f       stmia.w r4, {r0, r1, r2, r3} #            i_ctime
  26:   e886 000f       stmia.w r6, {r0, r1, r2, r3} #            i_mtime

and a slightly more verbose version of the same thing on x86
(storing only 12 bytes instead of 16 is cheaper there, while
ARM does a store-multiple to copy the entire structure).

        Arnd
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Re: [Y2038] [PATCH v2 00/24] Delete CURRENT_TIME and CURRENT_TIME_SEC macros

[Arnd Bergmann]

On Sunday, June 19, 2016 5:26:59 PM CEST Deepa Dinamani wrote:
> The series is aimed at getting rid of CURRENT_TIME and CURRENT_TIME_SEC macros.
> The macros are not y2038 safe. There is no plan to transition them into being
> y2038 safe.
> ktime_get_* api's can be used in their place. And, these are y2038 safe.
> 
> Thanks to Arnd Bergmann for all the guidance and discussions.
> 
> Patches 2-4 were mostly generated using coccinelle scripts.
> 
> All filesystem timestamps use current_fs_time() for right granularity as
> mentioned in the respective commit texts of patches. This has a changed
> signature, renamed to current_time() and moved to the fs/inode.c.
> 
> This series also serves as a preparatory series to transition vfs to 64 bit
> timestamps as outlined here: https://lkml.org/lkml/2016/2/12/104 .
> 
> As per Linus's suggestion in https://lkml.org/lkml/2016/5/24/663 , all the
> inode timestamp changes have been squashed into a single patch. Also,
> current_time() now is used as a single generic vfs filesystem timestamp api.
> It also takes struct inode* as argument instead of struct super_block*.
> Posting all patches together in a bigger series so that the big picture is
> clear.
> 
> As per the suggestion in https://lwn.net/Articles/672598/, CURRENT_TIME macro
> bug fixes are being handled in a series separate from transitioning vfs to use.

I've looked in detail at all the patches in this version now, and while
overall everything is fine, I found that two patches cannot be part of the
series because of the dependency on the patch that John already took (adding
time64_to_tm), but I think that's ok because we just need to change over
all the users of CURRENT_TIME and CURRENT_TIME_SEC that assign to inode
timestamps in order to prepare for the type change, the other ones
can be changed later.

I also found a few things that could be done differently to make the
later conversion slightly easier, but it's also possible that I missed
part of your bigger plan for those files, and none of them seem important.

	Arnd

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