[erlang-patches] [PATCH] Use share flags for all file operations on Windows

[Filipe David Manana]

On Wed, Oct 24, 2012 at 10:06 AM, Henrik Nord <henrik@REDACTED> wrote:
> Hi
>
> I have added your patch to 'master-pu'.

Thanks Henrik.

>
> If you are able to reproduce this we would love tests for it. We do however
> understand if you are not able to reproduce it consistently as it may be
> dependent on timings and whatnot.

Yes, it's very hard to reproduce it consistently. Basically what I
encountered was
that if an Erlang process is "in the middle of" a filelib:file_size/1
(indirectly uses
efile_fileinfo C function) call (after it opened the file, with share
flags set to 0,
and before it closes the file), other processes attempting to delete, rename or
even open the file for read only mode, fail with eacces error.

I noticed then that passing all the share flags to the CreateFileW
call in efile_fileinfo
was missing, as well as in a few other places other than efile_openfile.

>
> However, there is a vague feeling that this may have been tried before, and
> strange errors with "ghost" files that did not exist, but could not be
> created as the names where taken.

Yep, I think what you're mentioning relates to what is described in
these 2 pages:

http://social.msdn.microsoft.com/Forums/nl-BE/vcgeneral/thread/54bef96f-3ca1-4dd7-a621-da2fa8d8b35b
(reply from Friday, October 28, 2011 12:39 PM)

http://stackoverflow.com/questions/3764072/c-win32-how-to-wait-for-a-pending-delete-to-complete

Seems the solution is to rename a file and then delete it. However
without FILE_SHARE_DELETE, the rename
operation fails (if the file is already open without share delete
flag), as I experienced and is mentioned in Microsoft's
documentation for FILE_SHARE_DELETE:

http://msdn.microsoft.com/en-us/library/windows/desktop/aa363858(v=vs.85).aspx

It fails with ERROR_SHARING_VIOLATION, and then the win_efile module
translates it to EACCES.
Therefore I think this patch helps on that, but ultimately, due to
Windows specific file handling, the
rename + delete seems to be a common practice.

best regards,

>
>
>
>
> On 10/23/2012 07:56 PM, Filipe David Manana wrote:
>>
>>
>> https://github.com/fdmanana/otp/compare/maint...windows_file_share_delete.patch
>> https://github.com/fdmanana/otp/compare/maint...windows_file_share_delete
>>
>> git fetch git://github.com/fdmanana/otp.git windows_file_share_delete
>>
>>
>
> --
> /Henrik Nord Erlang/OTP
>



-- 
Filipe David Manana,

"Reasonable men adapt themselves to the world.
 Unreasonable men adapt the world to themselves.
 That's why all progress depends on unreasonable men."