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d651d1607f
linux/fs
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Arnd Bergmann d651d1607f vfs: replace current_kernel_time64 with ktime equivalent 
current_time is the last remaining caller of current_kernel_time64(),
which is a wrapper around ktime_get_coarse_real_ts64().  This calls the
latter directly for consistency with the rest of the kernel that is moving
to the ktime_get_ family of time accessors, as now documented in
Documentation/core-api/timekeeping.rst.

An open questions is whether we may want to actually call the more
accurate ktime_get_real_ts64() for file systems that save high-resolution
timestamps in their on-disk format.  This would add a small overhead to
each update of the inode stamps but lead to inode timestamps to actually
have a usable resolution better than one jiffy (1 to 10 milliseconds
normally).  Experiments on a variety of hardware platforms show a typical
time of around 100 CPU cycles to read the cycle counter and calculate the
accurate time from that.  On old platforms without a cycle counter, this
can be signiciantly higher, up to several microseconds to access a
hardware clock, but those have become very rare by now.

I traced the original addition of the current_kernel_time() call to set
the nanosecond fields back to linux-2.5.48, where Andi Kleen added a patch
with subject "nanosecond stat timefields".  Andi explains that the
motivation was to introduce as little overhead as possible back then.  At
this time, reading the clock hardware was also more expensive when most
architectures did not have a cycle counter.

One side effect of having more accurate inode timestamp would be having to
write out the inode every time that mtime/ctime/atime get touched on most
systems, whereas many file systems today only write it when the timestamps
have changed, i.e.  at most once per jiffy unless something else changes
as well.  That change would certainly be noticed in some workloads, which
is enough reason to not do it without a good reason, regardless of the
cost of reading the time.

One thing we could still consider however would be to round the timestamps
from current_time() to multiples of NSEC_PER_JIFFY, e.g.  full
milliseconds rather than having six or seven meaningless but confusing
digits at the end of the timestamp.

Link: http://lkml.kernel.org/r/20180726130820.4174359-1-arnd@arndb.de
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
2018-12-18 16:13:05 +01:00
..
9p Merge branch 'work.afs' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs 2018-11-01 19:58:52 -07:00
adfs adfs: use timespec64 for time conversion 2018-08-22 10:52:51 -07:00
affs affs: fix potential memory leak when parsing option 'prefix' 2018-05-28 12:36:41 +02:00
afs afs: Probe multiple fileservers simultaneously 2018-10-24 00:41:09 +01:00
autofs Merge branch 'akpm' (patches from Andrew) 2018-08-22 12:34:08 -07:00
befs fix a series of Documentation/ broken file name references 2018-06-15 18:10:01 -03:00
bfs bfs: add sanity check at bfs_fill_super() 2018-11-03 10:09:38 -07:00
btrfs vfs: rework data cloning infrastructure 2018-11-02 09:33:08 -07:00
cachefiles cachefiles: fix the race between cachefiles_bury_object() and rmdir(2) 2018-10-18 11:32:21 +02:00
ceph Merge branch 'work.afs' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs 2018-11-01 19:58:52 -07:00
cifs cifs: fix signed/unsigned mismatch on aio_read patch 2018-11-02 14:09:42 -05:00
coda vfs: change inode times to use struct timespec64 2018-06-05 16:57:31 -07:00
configfs configfs: fix registered group removal 2018-07-17 06:14:07 -07:00
cramfs Make the Cramfs code more robust against filesystem corruptions, 2018-10-30 12:46:25 -07:00
crypto crypto: speck - remove Speck 2018-09-04 11:35:03 +08:00
debugfs Revert "debugfs: inode: debugfs_create_dir uses mode permission from parent" 2018-06-12 20:52:16 -07:00
devpts devpts: Convert to new IDA API 2018-08-21 23:54:17 -04:00
dlm iov_iter: Separate type from direction and use accessor functions 2018-10-24 00:41:07 +01:00
ecryptfs ecryptfs_rename(): verify that lower dentries are still OK after lock_rename() 2018-10-09 23:33:17 -04:00
efivarfs efivars: Call guid_parse() against guid_t type of variable 2018-07-22 14:13:44 +02:00
efs
exofs fs/exofs: only use true/false for asignment of bool type variable 2018-10-18 02:04:59 -04:00
exportfs ovl: do not try to reconnect a disconnected origin dentry 2018-04-12 12:04:49 +02:00
ext2 \n 2018-10-29 10:23:36 -07:00
ext4 for-linus-20181102 2018-11-02 11:25:48 -07:00
f2fs Merge branch 'xarray' of git://git.infradead.org/users/willy/linux-dax 2018-10-28 11:35:40 -07:00
fat fat: truncate inode timestamp updates in setattr 2018-10-31 08:54:14 -07:00
freevxfs freevxfs_lookup(): use d_splice_alias() 2018-05-22 14:27:51 -04:00
fscache fscache: Fix out of bound read in long cookie keys 2018-10-18 11:32:21 +02:00
fuse Merge branch 'work.afs' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs 2018-11-01 19:58:52 -07:00
gfs2 Merge branch 'xarray' of git://git.infradead.org/users/willy/linux-dax 2018-10-28 11:35:40 -07:00
hfs fs/hfs/extent.c: fix array out of bounds read of array extent 2018-10-31 08:54:13 -07:00
hfsplus hfsplus: update timestamps on truncate() 2018-10-31 08:54:13 -07:00
hostfs vfs: discard ATTR_ATTR_FLAG 2018-08-17 16:20:28 -07:00
hpfs hpfs: remove unnecessary checks on the value of r when assigning error code 2018-08-25 12:42:33 -07:00
hugetlbfs mm: zero out the vma in vma_init() 2018-08-22 10:52:44 -07:00
isofs Update email address 2018-09-29 22:47:48 -04:00
jbd2 jbd2: fix use after free in jbd2_log_do_checkpoint() 2018-10-05 18:44:40 -04:00
jffs2 Merge branch 'siginfo-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/ebiederm/user-namespace 2018-10-24 11:22:39 +01:00
jfs jfs: remove redundant dquot_initialize() in jfs_evict_inode() 2018-09-20 09:28:49 -05:00
kernfs mm: zero-seek shrinkers 2018-10-26 16:26:33 -07:00
lockd lockd: fix access beyond unterminated strings in prints 2018-10-29 16:58:04 -04:00
minix minix_lookup: use d_splice_alias() 2018-05-22 14:27:52 -04:00
nfs NFS client bugfixes for Linux 4.20 2018-11-04 08:20:09 -08:00
nfs_common
nfsd vfs: rework data cloning infrastructure 2018-11-02 09:33:08 -07:00
nilfs2 nilfs2: Convert to XArray 2018-10-21 10:46:42 -04:00
nls
notify fsnotify: Fix busy inodes during unmount 2018-10-25 15:49:19 +02:00
ntfs ntfs: don't open-code ERR_CAST 2018-10-12 22:46:50 -04:00
ocfs2 ocfs2: fix clusters leak in ocfs2_defrag_extent() 2018-11-03 10:09:37 -07:00
omfs omfs_lookup(): report IO errors, use d_splice_alias() 2018-05-22 14:27:58 -04:00
openpromfs openpromfs: switch to d_splice_alias() 2018-05-22 14:27:57 -04:00
orangefs Merge branch 'work.afs' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs 2018-11-01 19:58:52 -07:00
overlayfs vfs: rework data cloning infrastructure 2018-11-02 09:33:08 -07:00
proc New gcc plugin: stackleak 2018-11-01 11:46:27 -07:00
pstore mm: remove CONFIG_HAVE_MEMBLOCK 2018-10-31 08:54:15 -07:00
qnx4 qnx4_lookup: use d_splice_alias() 2018-05-22 14:27:52 -04:00
qnx6 qnx6_lookup: switch to d_splice_alias() 2018-05-22 14:27:54 -04:00
quota fs/quota: Fix spectre gadget in do_quotactl 2018-08-22 18:17:48 +02:00
ramfs
reiserfs reiserfs: remove workaround code for GCC 3.x 2018-10-31 08:54:14 -07:00
romfs romfs_lookup: switch to d_splice_alias() 2018-05-22 14:27:55 -04:00
squashfs Squashfs: Compute expected length from inode size rather than block length 2018-08-02 09:34:02 -07:00
sysfs Driver core patches for 4.19-rc1 2018-08-18 11:44:53 -07:00
sysv fs/sysv/inode.c: use ktime_get_real_seconds() for superblock stamp 2018-08-22 10:52:51 -07:00
tracefs tracefs: Annotate tracefs_ops with __ro_after_init 2018-07-31 11:32:44 -04:00
ubifs ubifs: Remove unneeded semicolon 2018-10-23 13:49:02 +02:00
udf udf: Drop pack pragma from udf_sb.h 2018-09-07 10:32:23 +02:00
ufs fs/ufs: use ktime_get_real_seconds for sb and cg timestamps 2018-08-17 16:20:27 -07:00
xfs vfs: rework data cloning infrastructure 2018-11-02 09:33:08 -07:00
aio.c io_pgetevents: use __kernel_timespec 2018-12-06 17:23:31 +01:00
anon_inodes.c anon_inode_getfile(): switch to alloc_file_pseudo() 2018-07-12 10:04:27 -04:00
attr.c fs: Fix attr.c kernel-doc 2018-07-03 16:44:45 -04:00
bad_inode.c get rid of 'opened' argument of ->atomic_open() - part 3 2018-07-12 10:04:20 -04:00
binfmt_aout.c exec: introduce finalize_exec() before start_thread() 2018-04-11 10:28:37 -07:00
binfmt_elf_fdpic.c treewide: kmalloc() -> kmalloc_array() 2018-06-12 16:19:22 -07:00
binfmt_elf.c signal: Distinguish between kernel_siginfo and siginfo 2018-10-03 16:47:43 +02:00
binfmt_em86.c
binfmt_flat.c exec: introduce finalize_exec() before start_thread() 2018-04-11 10:28:37 -07:00
binfmt_misc.c turn filp_clone_open() into inline wrapper for dentry_open() 2018-07-10 23:29:03 -04:00
binfmt_script.c
block_dev.c iov_iter: Use accessor function 2018-10-24 00:40:44 +01:00
buffer.c for-linus-20181102 2018-11-02 11:25:48 -07:00
char_dev.c
compat_binfmt_elf.c y2038: globally rename compat_time to old_time32 2018-08-27 14:48:48 +02:00
compat_ioctl.c media updates for v4.20-rc1 2018-10-29 14:29:58 -07:00
compat.c ncpfs: remove compat functionality 2018-06-05 19:23:26 +02:00
coredump.c signal: Distinguish between kernel_siginfo and siginfo 2018-10-03 16:47:43 +02:00
d_path.c
dax.c dax: Convert page fault handlers to XArray 2018-10-21 10:46:44 -04:00
dcache.c mm: remove include/linux/bootmem.h 2018-10-31 08:54:16 -07:00
dcookies.c
direct-io.c iov_iter: Use accessor function 2018-10-24 00:40:44 +01:00
drop_caches.c
eventfd.c Revert changes to convert to ->poll_mask() and aio IOCB_CMD_POLL 2018-06-28 10:40:47 -07:00
eventpoll.c signal: Add restore_user_sigmask() 2018-12-06 17:22:53 +01:00
exec.c vfs: require i_size <= SIZE_MAX in kernel_read_file() 2018-10-10 12:56:14 -04:00
fcntl.c signal: Distinguish between kernel_siginfo and siginfo 2018-10-03 16:47:43 +02:00
fhandle.c
file_table.c overlayfs update for 4.19 2018-08-21 18:19:09 -07:00
file.c fs: add ksys_close() wrapper; remove in-kernel calls to sys_close() 2018-04-02 20:16:00 +02:00
filesystems.c proc: introduce proc_create_single{,_data} 2018-05-16 07:23:35 +02:00
fs_pin.c
fs_struct.c
fs-writeback.c fs: Convert writeback to XArray 2018-10-21 10:46:42 -04:00
inode.c vfs: replace current_kernel_time64 with ktime equivalent 2018-12-18 16:13:05 +01:00
internal.h overlayfs update for 4.19 2018-08-21 18:19:09 -07:00
ioctl.c vfs: rework data cloning infrastructure 2018-11-02 09:33:08 -07:00
iomap.c Merge branch 'work.misc' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs 2018-11-01 20:19:49 -07:00
Kconfig autofs: remove left-over autofs4 stubs 2018-06-11 08:22:34 -07:00
Kconfig.binfmt kconfig: move the "Executable file formats" menu to fs/Kconfig.binfmt 2018-08-02 08:06:55 +09:00
libfs.c
locks.c overlayfs update for 4.19 2018-08-21 18:19:09 -07:00
Makefile autofs: remove left-over autofs4 stubs 2018-06-11 08:22:34 -07:00
mbcache.c treewide: kmalloc() -> kmalloc_array() 2018-06-12 16:19:22 -07:00
mount.h
mpage.c mpage: mpage_readpages() should submit IO as read-ahead 2018-08-17 16:20:29 -07:00
namei.c namei: allow restricted O_CREAT of FIFOs and regular files 2018-08-23 18:48:43 -07:00
namespace.c mm: remove include/linux/bootmem.h 2018-10-31 08:54:16 -07:00
no-block.c
nsfs.c
open.c overlayfs update for 4.19 2018-08-21 18:19:09 -07:00
pipe.c Merge branch 'work.open3' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs 2018-08-13 19:58:36 -07:00
pnode.c
pnode.h
posix_acl.c
proc_namespace.c
read_write.c vfs: rework data cloning infrastructure 2018-11-02 09:33:08 -07:00
readdir.c fs: add ksys_getdents64() helper; remove in-kernel calls to sys_getdents64() 2018-04-02 20:16:02 +02:00
select.c pselect6: use __kernel_timespec 2018-12-06 17:23:18 +01:00
seq_file.c fs/seq_file.c: simplify seq_file iteration code and interface 2018-08-17 16:20:28 -07:00
signalfd.c signal: Distinguish between kernel_siginfo and siginfo 2018-10-03 16:47:43 +02:00
splice.c iov_iter: Separate type from direction and use accessor functions 2018-10-24 00:41:07 +01:00
stack.c
stat.c y2038: Remove newstat family from default syscall set 2018-08-29 15:42:20 +02:00
statfs.c kernel: add kcompat_sys_{f,}statfs64() 2018-07-12 14:49:48 +01:00
super.c fsnotify: add super block object type 2018-09-03 15:14:01 +02:00
sync.c Changes for this release: 2018-04-04 12:44:02 -07:00
timerfd.c y2038: globally rename compat_time to old_time32 2018-08-27 14:48:48 +02:00
userfaultfd.c userfaultfd: disable irqs when taking the waitqueue lock 2018-10-26 16:25:18 -07:00
utimes.c y2038: utimes: Rework #ifdef guards for compat syscalls 2018-08-29 15:42:23 +02:00
xattr.c sysfs: Do not return POSIX ACL xattrs via listxattr 2018-09-18 07:30:48 -04:00