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Tue, 28 Apr 2026 02:56:04 -0700 (PDT) From: Abd-Alrhman Masalkhi To: Yu Kuai , song@kernel.org Cc: linux-raid@vger.kernel.org, linux-kernel@vger.kernel.org, yukuai@fnnas.com Subject: Re: [PATCH] md: skip redundant raid_disks update when value is unchanged In-Reply-To: <9748ccf8-7d4f-495f-8083-eb640008f073@fnnas.com> References: <20260425085843.3725-1-abd.masalkhi@gmail.com> <9748ccf8-7d4f-495f-8083-eb640008f073@fnnas.com> Date: Tue, 28 Apr 2026 11:56:02 +0200 Message-ID: Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: quoted-printable On Tue, Apr 28, 2026 at 16:25 +0800, Yu Kuai wrote: > Hi, > > =E5=9C=A8 2026/4/25 16:58, Abd-Alrhman Masalkhi =E5=86=99=E9=81=93: >> Calling update_raid_disks() with the same value as the current one >> can trigger unnecessary work. For example, RAID1 will reallocate >> resources such as the mempool for r1bio. >> >> Signed-off-by: Abd-Alrhman Masalkhi >> --- >> It returns -EINVAL for the same value. If silent success is preferred >> instead, please let me know so I adjust its behavior. >> --- >> drivers/md/md.c | 9 ++++++--- >> 1 file changed, 6 insertions(+), 3 deletions(-) >> >> diff --git a/drivers/md/md.c b/drivers/md/md.c >> index 0e55639211f2..cb66c4ebbafa 100644 >> --- a/drivers/md/md.c >> +++ b/drivers/md/md.c >> @@ -4409,9 +4409,12 @@ raid_disks_store(struct mddev *mddev, const char = *buf, size_t len) >> err =3D mddev_suspend_and_lock(mddev); >> if (err) >> return err; >> - if (mddev->pers) >> - err =3D update_raid_disks(mddev, n); >> - else if (mddev->reshape_position !=3D MaxSector) { >> + if (mddev->pers) { >> + if (n !=3D mddev->raid_disks) >> + err =3D update_raid_disks(mddev, n); >> + else >> + err =3D -EINVAL; > > Changing return value in this case is not expected, especially from > success to failure. > I=E2=80=99ll adjust the behavior to return success instead. >> + } else if (mddev->reshape_position !=3D MaxSector) { >> struct md_rdev *rdev; >> int olddisks =3D mddev->raid_disks - mddev->delta_disks; >>=20=20=20 > > --=20 > Thansk, > Kuai --=20 Best Regards, Abd-Alrhman