[lkml]   [2015]   [May]   [7]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
Messages in this thread
SubjectRe: [PATCH RFC] vfs: add a O_NOMTIME flag
On Thu, May 7, 2015 at 12:09 PM, Richard Weinberger
<> wrote:
> On Thu, May 7, 2015 at 7:20 PM, Zach Brown <> wrote:
>> On Thu, May 07, 2015 at 10:26:17AM +1000, Dave Chinner wrote:
>>> On Wed, May 06, 2015 at 03:00:12PM -0700, Zach Brown wrote:
>>> > Add the O_NOMTIME flag which prevents mtime from being updated which can
>>> > greatly reduce the IO overhead of writes to allocated and initialized
>>> > regions of files.
>>> Hmmm. How do backup programs now work out if the file has changed
>>> and hence needs copying again? ie. applications using this will
>>> break other critical infrastructure in subtle ways.
>> By using backup infrastructure that doesn't use cmtime. Like btrfs
>> send/recv. Or application level backups that know how to do
>> incrementals from metadata in giant database files, say, without
>> walking, comparing, and copying the entire thing.
> But how can Joey random user know that some of his
> applications are using O_NOMTIME and his KISS backup
> program does no longer function as expected?

Joey random user can't have a working KISS backup anyway, though,
because we screw up mtime updates on mmap writes. I have patches
gathering dust that fix that, though.


 \ /
  Last update: 2015-05-07 22:01    [W:0.195 / U:22.140 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site