linux-kernel - RE: [RFC PATCH 1/2] 9p: retrieve fid from file when file instance exist.

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Message-ID: <HE1PR0802MB25556829FCB3A4171E3BDE9DF4910@HE1PR0802MB2555.eurprd08.prod.outlook.com>
Date:   Sun, 28 Jun 2020 06:51:26 +0000
From:   Jianyong Wu <Jianyong.Wu@....com>
To:     Dominique Martinet <asmadeus@...ewreck.org>
CC:     "ericvh@...il.com" <ericvh@...il.com>,
        "lucho@...kov.net" <lucho@...kov.net>,
        "v9fs-developer@...ts.sourceforge.net" 
        <v9fs-developer@...ts.sourceforge.net>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        Steve Capper <Steve.Capper@....com>,
        Kaly Xin <Kaly.Xin@....com>, Justin He <Justin.He@....com>,
        Wei Chen <Wei.Chen@....com>
Subject: RE: [RFC PATCH 1/2] 9p: retrieve fid from file when file instance
 exist.

Hi Dominique,

> -----Original Message-----
> From: Dominique Martinet <asmadeus@...ewreck.org>
> Sent: Sunday, June 28, 2020 2:28 PM
> To: Jianyong Wu <Jianyong.Wu@....com>
> Cc: ericvh@...il.com; lucho@...kov.net; v9fs-
> developer@...ts.sourceforge.net; linux-kernel@...r.kernel.org; Steve
> Capper <Steve.Capper@....com>; Kaly Xin <Kaly.Xin@....com>; Justin He
> <Justin.He@....com>; Wei Chen <Wei.Chen@....com>
> Subject: Re: [RFC PATCH 1/2] 9p: retrieve fid from file when file instance
> exist.
>
> Jianyong Wu wrote on Sun, Jun 28, 2020:
> > In the current setattr implementation in 9p, fid will always retrieved
> > from dentry no matter file instance exist or not when setattr. There
> > will be some info related to open file instance dropped. so it's
> > better to retrieve fid from file instance if file instance is passed to setattr.
> >
> > for example:
> > fd=open("tmp", O_RDWR);
> > ftruncate(fd, 10);
> >
> > the file context related with fd info will lost as fid will always be
> > retrieved from dentry, then the backend can't get the info of file context.
> > it is against the original intention of user and may lead to bug.
>
> I agree on principle, this makes more sense to use the file's fid.
>
Thanks!

> Just a comment below, but while I'm up in commit message I'll also be
> annoying with it -- please try to fix grammar mistakes for next
> patches/version (mostly missing some 'be' for future passive form; but I don't
> understand why you use future at all and some passive forms could probably
> be made active to simplify... Anyway we're not here to discuss English
> grammar but words missing out is sloppy and that gives a bad impression for
> no good reason)
>
Sorry to my poor English and thanks to point out the grammar mistakes,  I'll fix it.

> >
> > Signed-off-by: Jianyong Wu <jianyong.wu@....com>
> > ---
> >  fs/9p/vfs_inode.c      | 5 ++++-
> >  fs/9p/vfs_inode_dotl.c | 5 ++++-
> >  2 files changed, 8 insertions(+), 2 deletions(-)
> >
> > diff --git a/fs/9p/vfs_inode.c b/fs/9p/vfs_inode.c index
> > c9255d399917..010869389523 100644
> > --- a/fs/9p/vfs_inode.c
> > +++ b/fs/9p/vfs_inode.c
> > @@ -1100,7 +1100,10 @@ static int v9fs_vfs_setattr(struct dentry
> > *dentry, struct iattr *iattr)
> >
> >  retval = -EPERM;
> >  v9ses = v9fs_dentry2v9ses(dentry);
> > -fid = v9fs_fid_lookup(dentry);
> > +if (iattr->ia_valid & ATTR_FILE)
> > +fid = iattr->ia_file->private_data;
>
> hmm, normally setattr cannot happen on a file that hasn't been opened so
> private_data should always be set, but it doesn't cost much to play safe and
> check? e.g. something like this is more conservative:
>
> struct p9_fid *fid = NULL;
> ...
> if (iattr->ia_valid & ATTR_FILE) {
> fid = iattr->ia_file->private_data;
> WARN_ON(!fid);
> }
> if (!fid)
> fid = v9fs_fid_lookup(dentry);
>
>
>
> What do you think?
>
Thanks, I think it's better. I'll take it.

Thanks
Jianyong

> --
> Dominique
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