linux-kernel - RE: [GIT PULL] iomap: new code for 5.13-rc1

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Message-ID: <AM6PR08MB43769965CAF732F1DEA4A37AF75E9@AM6PR08MB4376.eurprd08.prod.outlook.com>
Date:   Fri, 30 Apr 2021 03:17:02 +0000
From:   Justin He <Justin.He@....com>
To:     Linus Torvalds <torvalds@...ux-foundation.org>,
        Rasmus Villemoes <linux@...musvillemoes.dk>
CC:     Christoph Hellwig <hch@....de>,
        "Darrick J. Wong" <djwong@...nel.org>,
        Al Viro <viro@...iv.linux.org.uk>,
        linux-fsdevel <linux-fsdevel@...r.kernel.org>,
        linux-xfs <linux-xfs@...r.kernel.org>,
        Dave Chinner <david@...morbit.com>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Eric Sandeen <sandeen@...deen.net>,
        Andy Shevchenko <andy.shevchenko@...il.com>
Subject: RE: [GIT PULL] iomap: new code for 5.13-rc1

Hi

> -----Original Message-----
> From: Linus Torvalds <torvalds@...ux-foundation.org>
> Sent: Friday, April 30, 2021 12:46 AM
> To: Rasmus Villemoes <linux@...musvillemoes.dk>
> Cc: Christoph Hellwig <hch@....de>; Darrick J. Wong <djwong@...nel.org>;
> Justin He <Justin.He@....com>; Al Viro <viro@...iv.linux.org.uk>; linux-
> fsdevel <linux-fsdevel@...r.kernel.org>; linux-xfs <linux-
> xfs@...r.kernel.org>; Dave Chinner <david@...morbit.com>; Linux Kernel
> Mailing List <linux-kernel@...r.kernel.org>; Eric Sandeen
> <sandeen@...deen.net>; Andy Shevchenko <andy.shevchenko@...il.com>
> Subject: Re: [GIT PULL] iomap: new code for 5.13-rc1
>
> On Wed, Apr 28, 2021 at 11:40 PM Rasmus Villemoes
> <linux@...musvillemoes.dk> wrote:
> >
> > > That also does explain the arguably odd %pD defaults: %pd came first,
> > > and then %pD came afterwards.
> >
> > Eh? 4b6ccca701ef5977d0ffbc2c932430dea88b38b6 added them both at the same
> > time.
>
> Ahh, I looked at "git blame", and saw that file_dentry_name() was
> added later. But that turns out to have been an additional fix on top,
> not actually "later support".
>
> Looking more at that code, I am starting to think that
> "file_dentry_name()" simply shouldn't use "dentry_name()" at all.
> Despite that shared code origin, and despite that similar letter
> choice (lower-vs-upper case), a dentry and a file really are very very
> different from a name standpoint.
>
> And it's not the "a filename is the whale pathname, and a dentry has
> its own private dentry name" issue. It's really that the 'struct file'
> contains a _path_ - which is not just the dentry pointer, but the
> 'struct vfsmount' pointer too.
>
> So '%pD' really *could* get the real path right (because it has all
> the required information) in ways that '%pd' fundamentally cannot.
>
> At the same time, I really don't like printk specifiers to take any
> real locks (ie mount_lock or rename_lock), so I wouldn't want them to
> use the full  d_path() logic.

Is it a good idea to introduce a new d_path_nolock() for file_dentry_name()?
In d_path_nolock(), if it detects that there is conflicts with mount_lock
or rename_lock, then returned NULL as a name of that vfsmount?

Thanks for further suggestion.

--
Cheers,
Justin (Jia He)


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