lkml.org 
[lkml]   [2013]   [Jan]   [18]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
SubjectRe: [PATCH v2 0/8] Add O_DENY* support for VFS and CIFS/NFS
From
2013/1/18 Stephen Rothwell <sfr@canb.auug.org.au>:
> Hi Pavel,
>
> On Thu, 17 Jan 2013 20:52:09 +0400 Pavel Shilovsky <piastry@etersoft.ru> wrote:
>>
>> This patchset adds support of O_DENY* flags for Linux fs layer. These flags can be used by any application that needs share reservations to organize a file access. VFS already has some sort of this capability - now it's done through flock/LOCK_MAND mechanis, but that approach is non-atomic. This patchset build new capabilities on top of the existing one but doesn't bring any changes into the flock call semantic.
>
> This has probably been discussed, but is Linux's leases implementation
> not sufficient? Just wondering.

As I understand it, leases play different role: they allow to cache a
data for the particular open and then flush it when a lease break
comes. But we need to protect opens from being done if their
access/share mode is not suitable for previously done opens. E.g. if
we have already opened a file with O_RDONLY | O_DENYWRITE we can't
open it again with any of O_WRONLY, O_RDWR and O_DENYREAD flags (of
course all these things should only work if O_DENYMAND is specified
for the first and the second opens).

--
Best regards,
Pavel Shilovsky.


\
 
 \ /
  Last update: 2013-01-18 08:21    [W:0.139 / U:1.520 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site