From: Eric Sandeen Subject: Re: [PATCH] mm: reject MAP_SHARED_VALIDATE without new flags Date: Wed, 27 Jun 2018 21:17:55 -0500 Message-ID: <1e2ad827-6ff4-4b1e-c4d9-79ca4e432a6c@sandeen.net> References: <60052659-7b37-cb69-bf9f-1683caa46219@redhat.com> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Cc: Christoph Hellwig , Jan Kara , "linux-nvdimm-hn68Rpc1hR1g9hUCZPvPmw@public.gmane.org" , Linux API , zhibli-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org, linux-xfs , linux-mm , linux-fsdevel , linux-ext4-u79uwXL29TY76Z2rM5mHXA@public.gmane.org To: Linus Torvalds , Eric Sandeen Return-path: In-Reply-To: Content-Language: en-US List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: linux-nvdimm-bounces-hn68Rpc1hR1g9hUCZPvPmw@public.gmane.org Sender: "Linux-nvdimm" List-Id: linux-ext4.vger.kernel.org On 6/27/18 9:10 PM, Linus Torvalds wrote: > On Wed, Jun 27, 2018 at 6:45 PM Eric Sandeen wrote: >> >> Thus the invalid flag combination of (MAP_SHARED|MAP_PRIVATE) now >> passes without error, which is a regression. > > It's not a regression, it's just new behavior. > > "regression" doesn't mean "things changed". It means "something broke". > > What broke? My commit log perhaps was not clear enough. What broke is that mmap(MAP_SHARED|MAP_PRIVATE) now succeeds without error, whereas before it rightly returned -EINVAL. What behavior should a user expect from a successful mmap(MAP_SHARED|MAP_PRIVATE)? -Eric > Because if it's some manual page breakage, just fix the manual. That's > what "new behavior" is all about. > > There is nothing that says that "MAP_SHARED_VALIDATE" can't work with > just the legacy flags. > > Because I'd be worried about your patch breaking some actual new user > of MAP_SHARED_VALIDATE. > > Because it's actual *users* of behavior we care about, not some > test-suite or manual pages. > > Linus