linux-kernel - Re: [RESEND PATCH v2] kernfs: fix dentry unexpected skip

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Message-ID: <20180529162627.GH1351649@devbig577.frc2.facebook.com>
Date:   Tue, 29 May 2018 09:26:27 -0700
From:   "'tj@...nel.org'" <tj@...nel.org>
To:     "Hatayama, Daisuke" <d.hatayama@...fujitsu.com>
Cc:     "'gregkh@...uxfoundation.org'" <gregkh@...uxfoundation.org>,
        "Okajima, Toshiyuki" <toshi.okajima@...fujitsu.com>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "'ebiederm@...stanetworks.com'" <ebiederm@...stanetworks.com>
Subject: Re: [RESEND PATCH v2] kernfs: fix dentry unexpected skip

Hello,

On Mon, May 28, 2018 at 12:54:03PM +0000, Hatayama, Daisuke wrote:
> diff --git a/fs/kernfs/dir.c b/fs/kernfs/dir.c
> index 89d1dc1..3aeeb7a 100644
> --- a/fs/kernfs/dir.c
> +++ b/fs/kernfs/dir.c
> @@ -1621,8 +1621,10 @@ static int kernfs_dir_fop_release(struct inode *inode, struct file *filp)
>  static struct kernfs_node *kernfs_dir_next_pos(const void *ns,
>  	struct kernfs_node *parent, ino_t ino, struct kernfs_node *pos)
>  {
> +	struct kernfs_node *orig = pos;
> +
>  	pos = kernfs_dir_pos(ns, parent, ino, pos);
> -	if (pos) {
> +	if (pos && kernfs_sd_compare(pos, orig) <= 0) {

Hmm... the code seems a bit unintuitive to me and I wonder whether
it's because there are two identical skipping loops in
kernfs_dir_pos() and kernfs_dir_next_pos() and we're now trying to
selectively disable one of them.  Wouldn't it make more sense to get
rid of it from kernfs_dir_pos() and skip explicitly only when
necessary?

Thanks.

-- 
tejun