linux-kernel - Re: [PATCH v5 1/7] fs: introduce kernel_pread

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Date:   Wed, 13 May 2020 08:51:33 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     Scott Branden <scott.branden@...adcom.com>
Cc:     Luis Chamberlain <mcgrof@...nel.org>,
        Mimi Zohar <zohar@...ux.vnet.ibm.com>,
        David Brown <david.brown@...aro.org>,
        Alexander Viro <viro@...iv.linux.org.uk>,
        Shuah Khan <shuah@...nel.org>, bjorn.andersson@...aro.org,
        Shuah Khan <skhan@...uxfoundation.org>,
        Arnd Bergmann <arnd@...db.de>,
        "Rafael J . Wysocki" <rafael@...nel.org>,
        linux-kernel@...r.kernel.org, linux-arm-msm@...r.kernel.org,
        linux-fsdevel@...r.kernel.org,
        BCM Kernel Feedback <bcm-kernel-feedback-list@...adcom.com>,
        Olof Johansson <olof@...om.net>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Dan Carpenter <dan.carpenter@...cle.com>,
        Colin Ian King <colin.king@...onical.com>,
        Kees Cook <keescook@...omium.org>,
        Takashi Iwai <tiwai@...e.de>, linux-kselftest@...r.kernel.org,
        Andy Gross <agross@...nel.org>
Subject: Re: [PATCH v5 1/7] fs: introduce kernel_pread_file* support

On Tue, May 12, 2020 at 11:23:27PM -0700, Scott Branden wrote:
> Hi Luis,
> 
> A few comments inline before I cleanup.
> 
> On 2020-05-12 5:27 p.m., Luis Chamberlain wrote:
> > On Thu, May 07, 2020 at 05:27:33PM -0700, Scott Branden wrote:
> > > diff --git a/fs/exec.c b/fs/exec.c
> > > index 06b4c550af5d..cfab212fab9d 100644
> > > --- a/fs/exec.c
> > > +++ b/fs/exec.c
> > > @@ -896,10 +896,14 @@ struct file *open_exec(const char *name)
> > >   }
> > >   EXPORT_SYMBOL(open_exec);
> > > -int kernel_read_file(struct file *file, void **buf, loff_t *size,
> > > -		     loff_t max_size, enum kernel_read_file_id id)
> > > -{
> > > -	loff_t i_size, pos;
> > > +int kernel_pread_file(struct file *file, void **buf, loff_t *size,
> > > +		      loff_t pos, loff_t max_size, unsigned int flags,
> > You use int flags, but.. these are mutually exclusive operations, and
> > so flags is a misnomer. Just use an enum instead of a define, that way
> > we can use kdoc for documentation.
> OK, flags could be used to expand with additional flag options in the future
> (without change to function prototype, but will change to enum if that is
> what is desired.
> > > +EXPORT_SYMBOL_GPL(kernel_pread_file);
> > > +EXPORT_SYMBOL_GPL(kernel_pread_file_from_path);
> > > +EXPORT_SYMBOL_GPL(kernel_pread_file_from_path_initns);
> > > +EXPORT_SYMBOL_GPL(kernel_pread_file_from_fd);
> > If no one is using these don't export them. I think you only use one of
> > these. In fact just remove the code from the ones which are not used.
> I do not use them but added them to provide consistent api with
> kernel_read_file_* functions.  That way someone can take advantage of the
> _from_path and from_fd variants in the future if desired. But if you want
> them removed it is simple to drop the EXPORT_SYMBOL_GPL and then add that
> back when first driver that calls them needs them in the future.

We do not export symbols when there are no in-kernel users.

> Note: Existing kernel_read_file_from_path_initns is not used in the kernel. 
> Should we delete that as well?

Probably, yes.

thanks,

greg k-h