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rfjakob opened this issue Sep 28, 2015 · 11 comments
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syscall: NsecToTimeval does not handle times before 1970 #12777

rfjakob opened this issue Sep 28, 2015 · 11 comments
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FrozenDueToAge NeedsFix The path to resolution is known, but the work has not been done.
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Go1.8

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@rfjakob
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rfjakob commented Sep 28, 2015

Passing a time before 1970 means that nsec is negative.

This means that the rounding will not work properly, and the returned tv.Usec will be negative.

A negative tv.Usec is invalid and rejected by the Linux kernel with EINVAL.

Source code for reference: https://github.com/golang/go/blob/master/src/syscall/syscall_linux_amd64.go#L96
@rfjakob
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rfjakob commented Sep 28, 2015

This breaks setting of file timestamps in go-fuse, downstream bug: hanwen/go-fuse#58

@bradfitz bradfitz changed the title syscall.NsecToTimeval does not handle times before 1970 syscall: NsecToTimeval does not handle times before 1970 Sep 28, 2015
@ianlancetaylor
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What do you think should happen? It seems to me that having the kernel return EINVAL is correct.

@ianlancetaylor ianlancetaylor added this to the Unplanned milestone Sep 28, 2015
@rfjakob
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rfjakob commented Sep 29, 2015

tv.Sec should be negative but tv.Usec should be positive.

@rfjakob
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rfjakob commented Sep 29, 2015

Testcase: https://gist.github.com/rfjakob/6d3359a97d22f32083bc

 t=1960-01-10 23:00:00 +0000 UTC 
 nsec=-314758800000000000 
 tv.Sec=-314758799 tv.Usec=-999999

tv.Sec and tv.Usec are both wrong. It should be:

tv.Sec=-314758800 tv.Usec=0

@hanwen
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hanwen commented Sep 29, 2015

nsectotimeval should do

if (tv.usec < 0) {
tv.usec += 1e6
tv.sec --
}

@hanwen
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hanwen commented Sep 29, 2015

the same holds for NsecToTimeSpec.

func main() {
name := "test.txt"
var utimes [2]syscall.Timespec

f:=  time.FixedZone("bla",1) 
atime := time.Date(1968, 06, 18, 0, 0, 0, 99, f)
mtime := atime
utimes[0] = syscall.NsecToTimespec(atime.UnixNano())
utimes[1] = syscall.NsecToTimespec(mtime.UnixNano())

if e := syscall.UtimesNano(name, utimes[0:]); e != nil {
    log.Fatal(e)
}

}
=>
[hanwen@pomba test]$ go run tv.go
2015/09/29 08:38:00 invalid argument
exit status 1

@hanwen
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hanwen commented Sep 29, 2015

I can prepare a patch if you want.

@rfjakob
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rfjakob commented Sep 29, 2015

@hanwen I think the rounding should also be the other way round if nsec is negative

I noticed that the Linux kernel rounds DOWN while we round UP, check out http://lxr.free-electrons.com/source/kernel/time/time.c#L422 . This is unrelated, but it may be an opportunity to fix this as well.

rfjakob added a commit to rfjakob/go-fuse that referenced this issue Sep 29, 2015
@rfjakob
loopback: Replace buggy syscall.NsecToTimeval()
01a124c 
syscall.NsecToTimespec does not work properly for times
before 1970, see golang/go#12777

This caused xfstests generic/258 to fail.

Fixes issue hanwen#58.
@rfjakob rfjakob mentioned this issue Sep 29, 2015
Merged
rfjakob added a commit to rfjakob/go-fuse that referenced this issue Sep 29, 2015
@rfjakob
loopback: Replace buggy syscall.NsecToTimeval()
fe5b07b 
syscall.NsecToTimespec does not work properly for times
before 1970, see golang/go#12777

This caused xfstests generic/258 to fail.

Fixes issue hanwen#58.
rfjakob added a commit to rfjakob/go-fuse that referenced this issue Sep 29, 2015
@rfjakob
loopback: Replace buggy syscall.NsecToTimeval()
065c591 
syscall.NsecToTimespec does not work properly for times
before 1970, see golang/go#12777

This caused xfstests generic/258 to fail.

Fixes issue hanwen#58.
@rfjakob
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rfjakob commented Aug 9, 2016

Ping? NsecToTimeval is still broken.

@bradfitz bradfitz modified the milestones: Go1.8, Unplanned Aug 9, 2016
rfjakob added a commit to rfjakob/go-fuse that referenced this issue Aug 9, 2016
@rfjakob
loopback: re-enable nanoseconds for dates after 1970
ebec275 
For dates before 1970, syscall.NsecToTimespec() incorrectly
returns negative nanoseconds.
Ticket: golang/go#12777

Handle that case by zeroing out Nsec if it is negative,
but otherwise keep the value.

This makes nanoseconds work for the vast majority of use
cases.
@rfjakob rfjakob mentioned this issue Aug 9, 2016
Closed
@quentinmit quentinmit added the NeedsFix The path to resolution is known, but the work has not been done. label Oct 10, 2016
@quentinmit quentinmit self-assigned this Oct 10, 2016
@gopherbot
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CL https://golang.org/cl/30705 mentions this issue.

@quentinmit
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Fixed by 6c517df

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