1657663 - Improve resolution of file times as set/get by nsLocalFile on unix

Status: RESOLVED FIXED

(Core :: XPCOM, enhancement)

Description

[Keefer Rourke]

The current Unix implementation of nsLocalFile::SetLastModifiedTime sets file times with the legacy utime (2) system call, which is limited to a resolution of 1 second. Similarly when accessing these values with nsLocalFile::GetLastModifiedTime, the implementation uses the legacy stat.st_atime and stat.st_mtime members which represent file access/modification times in seconds since epoch.

The current implementation is problematic, since these APIs accept a PRTime value specified in milliseconds since epoch. The caller will have its set/get values silently truncated to the closest second.

We can update the implementations of SetLastModifiedTime and GetLastModifiedTime to use the utimes (2) family of system calls instead, which allow for up to 1 microsecond resolution with the timeval struct.

This change will also bring the unix implementation of nsLocalFile in line with the windows implementation, which does not truncate the file modification times during get/set operations.

Comment 1

[Keefer Rourke]

Attachment: Bug 1657663: Improve timestamp precision for nsLocalFileUnix r?barret!,froydnj

This change updates the unix implementation of nsLocalFile
Set/GetLastModifiedTime methods to improve the precision of file modification
times from a 1 second resolution to a 1 millisecond resolution.

Comment 2

[Pulsebot]

Pushed by [e-mail]:
https://hg.mozilla.org/integration/autoland/rev/60059f7d5c46
Improve timestamp precision for nsLocalFileUnix r=froydnj,barret

Comment 3

[Razvan Maries]

Backed out for perma failures.

Push with failure: https://treeherder.mozilla.org/#/jobs?repo=autoland&selectedTaskRun=ZdEYr27wTrmMnwX0-iI90A.0&resultStatus=pending%2Crunning%2Csuccess%2Ctestfailed%2Cbusted%2Cexception&searchStr=linux%2C18.04%2Cx64%2Cdebug%2Cxpcshell%2Ctests%2Cwith%2Cnetworking%2Con%2Csocket%2Cprocess%2Ctest-linux1804-64%2Fdebug-xpcshell-spi-nw-e10s%2Cx4&revision=60059f7d5c464eb10d7979cefb4d151bf50b5abf

Log: https://treeherder.mozilla.org/logviewer.html#/jobs?job_id=312636569&repo=autoland&lineNumber=3568

Backout: https://hg.mozilla.org/integration/autoland/rev/73e37f6a354cac4e8a522a10ebac59c2f14017c8

Comment 4

[Keefer Rourke]

Attachment: Bug 1657663: Update OS.File.setDates precision and fix failing extension tests r?barret,froydnj

This changes fixes some failing extension tests on unixes. These failures were
caused by a mismatch in time precision used by nsIFile and OS.File's
implementations.

The fixes are as follows:

1. Use IOUtils (the C++ port of OS.File) methods where possible.
2. Update the OS.File.setDates implementation to use a higher time precision
   when setDates is called. This is an intermediate measure until IOUtils
   itself has the ability to update file times.

Depends on D86238

Comment 5

[Pulsebot]

Pushed by [e-mail]:
https://hg.mozilla.org/integration/autoland/rev/f9c823fa14ba
Improve timestamp precision for nsLocalFileUnix r=froydnj,barret
https://hg.mozilla.org/integration/autoland/rev/e3dd5b6b4fbd
Update OS.File.setDates precision and fix failing extension tests r=barret,mixedpuppy

Comment 6

[Razvan Maries]

Backed out for perma failures. See https://bugzilla.mozilla.org/show_bug.cgi?id=1660328#c5

Comment 7

[Pulsebot]

Pushed by [e-mail]:
https://hg.mozilla.org/integration/autoland/rev/724b9714bc47
Improve timestamp precision for nsLocalFileUnix r=froydnj,barret
https://hg.mozilla.org/integration/autoland/rev/f8d98e224ebc
Update OS.File.setDates precision and fix failing extension tests r=barret,mixedpuppy

Comment 8

[Cristina Coroiu [:ccoroiu]]

https://hg.mozilla.org/mozilla-central/rev/724b9714bc47
https://hg.mozilla.org/mozilla-central/rev/f8d98e224ebc