From mboxrd@z Thu Jan 1 00:00:00 1970 From: Phil Turmel Subject: Re: mdadm: Patch to restrict --size when shrinking unless forced Date: Mon, 9 Oct 2017 16:04:10 -0400 Message-ID: References: <22997.8664.67459.119616@quad.stoffel.home> <87a81637lq.fsf@notabene.neil.brown.name> <23002.37193.492253.120639@quad.stoffel.home> <87shetz207.fsf@notabene.neil.brown.name> <23002.53075.413063.6948@quad.stoffel.home> <87h8v9yn91.fsf@notabene.neil.brown.name> Mime-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <87h8v9yn91.fsf@notabene.neil.brown.name> Content-Language: en-GB Sender: linux-raid-owner@vger.kernel.org To: NeilBrown , John Stoffel Cc: Eli Ben-Shoshan , Jes.Sorensen@gmail.com, linux-raid@vger.kernel.org List-Id: linux-raid.ids On 10/09/2017 12:10 AM, NeilBrown wrote: > If there is some action that mdadm can currently be told to perform, and > when it tries to perform that action it corrupts the array, then > it is certainly appropriate to teach mdadm not to perform that action. > It shouldn't even perform that action with --force. I agree that > changing mdadm like this is complementary to changing the kernel. Both > are useful. A certain amount of the trouble with all of this is the english meaning of "grow" doesn't really match what mdadm allows. Might it be reasonable to reject "--grow" operations that reduce the final array size, and introduce the complementary "--reduce" operation that rejects array size increases? Both operations would share the current code, just apply a different sanity check before proceeding. mdadm would then at least not violate the rule of least surprise. Phil