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Re: Respecting inherited Windows file permissions on file create

From: Branko Čibej <brane_at_wandisco.com>
Date: Mon, 30 Sep 2013 07:26:04 +0200

On 29.09.2013 23:15, Ivan Zhakov wrote:
> On 29 September 2013 18:49, Branko Čibej <brane_at_wandisco.com> wrote:
>> On 29.09.2013 16:06, Jason Kresowaty wrote:
>> The solution Ivan mentioned of creating a temp file in the same directory as
>> the final file is common.
>> I agree this is something we can look at. There were good reasons to not
>> create temporary files in the target directories, but we can certainly
>> revisit those reasons.
> Brane, do you remember reasons for creating temporary files in
> .svn/tmp instead of target directory? Is it pre-wcng decision?

Ben already answered this question. I'd like to point out that this
/may/ be a regression from 1.6: in the old working copy, the temporary
files were created in the current directory's .svn/tmp, not in the root
of the working copy. So, ACLs set on the parent were most likely
inherited correctly.

There's still a way to create temporary files with the correct security
attributes but without most of the problems that Ben mentioned: create
the empty tempfile in the target directory, then immediately move it to
<wcroot>/.svn/tmp. The final installation remains atomic, and the file
will have the correct ACLs. Unfortunately, there's a short period of
time when the new file is visible, two moves are of course more
expensive than one, and recovery from failure is more complex.

There's another problem with this approach on Windows: unlike on Unix,
you cannot rename an open file. Instead of the current
open/write/close/move sequence, you'd have
create/close/move/open/write/close/move, which is three more system
calls. That's not cheap.

The visibility problem can be easily solved by making the initial
tempfile names predictable (using a common prefix, for example).

-- Brane

Branko Čibej | Director of Subversion
WANdisco // Non-Stop Data
e. brane_at_wandisco.com
Received on 2013-09-30 07:27:47 CEST

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