Re: [RFC PATCH 0/4] 9pfs: Add 9pfs support for Windows host

From: Christian Schoenebeck <qemu_oss@crudebyte.com>
To: "Shi, Guohuai" <Guohuai.Shi@windriver.com>
Cc: Mark Cave-Ayland <mark.cave-ayland@ilande.co.uk>,
	qemu-devel@nongnu.org, Bin Meng <bmeng.cn@gmail.com>,
	Greg Kurz <groug@kaod.org>
Subject: Re: [RFC PATCH 0/4] 9pfs: Add 9pfs support for Windows host
Date: Tue, 19 Apr 2022 15:50:25 +0200	[thread overview]
Message-ID: <2766319.qo5tFDDxnU@silver> (raw)
In-Reply-To: <CH2PR11MB44546FDCE43D78D455491310EFF29@CH2PR11MB4454.namprd11.prod.outlook.com>

On Dienstag, 19. April 2022 13:10:40 CEST Shi, Guohuai wrote:
> Hi All,
> 
> I just finished a basic PoC for mapped-file.
> It works! I think I can also support "security_model=map-xattr" by NTFS
> ADS.

Slick!

> However, I got a limitation of MinGW:
> 
> https://github.com/mirror/mingw-w64/blob/master/mingw-w64-crt/misc/dirent.c#
> L290
>  
> MinGW can not handle seekdir() while the directory has changed.
> That means, if run command like "rm -rf *", MinGW may not delete all files.
> "rm -rf *" need to call readdir()(and call seekdir() in 9P) and unlink(),
> and MinGW's seekdir() may seek directory to wrong directory entry index. 
> I am considering to change 9PFS readdir() implement on Windows host, to fix
> this problem.

To avoid history repeating [1]: please do not attempt to address this in 9p.c!
That file is the controller portion of 9p server and must remain fs-agnostic.
Such kind of issue should rather be addressed on fs driver level
(e.g. 9p-local.c, 9p-util-windows.c).

I.e. don't do it like this:
[1] https://lore.kernel.org/all/20211122004913.20052-1-wwcohen@gmail.com/T/#m734f405973768e43ce3ed7550bd21809abb25813

Best regards,
Christian Schoenebeck