Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 2620:137:e000::1:20 as permitted sender) client-ip=2620:137:e000::1:20;
MIME-Version: 1.0
References: <CACGdZYLMW2KHVebfyJZVn9G=15N+Jt4+8oF5gq3wdDTOcXbk9A@mail.gmail.com>
 <20220513174030.1307720-1-khazhy@google.com> <20220517061238.GB4789@lst.de>
In-Reply-To: <20220517061238.GB4789@lst.de>
From:   Khazhy Kumykov <khazhy@google.com>
Date:   Mon, 16 May 2022 23:27:09 -0700
Message-ID: <CACGdZYLJjLyKHSSuTJH3_++NufsjDGjdz4vZwj0GKSiYQEvWpA@mail.gmail.com>
Subject: Re: [RESEND][RFC PATCH] blkcg: rewind seq_file if no stats
To:     Christoph Hellwig <hch@lst.de>
Cc:     Tejun Heo <tj@kernel.org>, Jens Axboe <axboe@kernel.dk>,
        Alexander Viro <viro@zeniv.linux.org.uk>,
        linux-block@vger.kernel.org, linux-fsdevel@vger.kernel.org,
        linux-kernel@vger.kernel.org, cgroups@vger.kernel.org
Content-Type: multipart/signed; protocol="application/pkcs7-signature"; micalg=sha-256;
        boundary="000000000000ab12ee05df2f3b4f"
Precedence: bulk

--000000000000ab12ee05df2f3b4f
Content-Type: text/plain; charset="UTF-8"

On Mon, May 16, 2022 at 11:12 PM Christoph Hellwig <hch@lst.de> wrote:
>
> On Fri, May 13, 2022 at 10:40:30AM -0700, Khazhismel Kumykov wrote:
> > Restores the previous behavior of only displaying devices for which we
> > have statistics (and removes the current, broken, behavior of printing
> > devname with no newline if no statistics)
> >
> > In lieu of get_seq_buf + seq_commit, provide a way to "undo" writes if
> > we use seq_printf
>
> I have to say I much prefer the simpler fix from Wolfgang.  But
Wolfgang's fix still results in a change in behavior, and in my
opinion a worse behavior - we don't need to print out the device names
if there are no stats.

> if we want to go down this route it needs to split into a patch
> for the seq_file infrastruture and a separate one for the blk-cgroup
> code.
Of course - I can spin this into a series if we think it's worthwhile

--000000000000ab12ee05df2f3b4f
Content-Type: application/pkcs7-signature; name="smime.p7s"
Content-Transfer-Encoding: base64
Content-Disposition: attachment; filename="smime.p7s"
Content-Description: S/MIME Cryptographic Signature
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--000000000000ab12ee05df2f3b4f--