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: <20220621084238.1235880-1-zhangshida@kylinos.cn> <YrKdZc0fBBDWGjld@magnolia>
In-Reply-To: <YrKdZc0fBBDWGjld@magnolia>
From:   Stephen Zhang <starzhangzsd@gmail.com>
Date:   Wed, 22 Jun 2022 13:57:31 +0800
Message-ID: <CANubcdXyM2t0M0Ks3=6Hm12_SVm50vGaTBboj5CBF2LygOkUog@mail.gmail.com>
Subject: Re: [PATCH v3] xfs: add check before calling xfs_mod_fdblocks
To:     "Darrick J. Wong" <djwong@kernel.org>
Cc:     dchinner@redhat.com, zhangshida <zhangshida@kylinos.cn>,
        linux-kernel@vger.kernel.org, linux-xfs@vger.kernel.org
Content-Type: text/plain; charset="UTF-8"
Precedence: bulk

> I understand that calling __xfs_ag_resv_init on an AG with a maximally
> sized data structure can result in @hidden_space being zero here, but
> why does that matter enough to change the code?  Are you experiencing
> problems when this happens?  Unnecessary slowdowns at mount time?
> Something else?
>
> This is v3 of a patch and I still can't tell why I should care ...?

After applying this patch, we can avoid to call xfs_mod_fdblocks when
delta equals 0. So we can reduce unnecessary operations here.