From mboxrd@z Thu Jan 1 00:00:00 1970 From: Rik van Riel Subject: Re: [FYI] tux3: Core changes Date: Wed, 20 May 2015 15:53:16 -0400 Message-ID: <555CE62C.5030202@redhat.com> References: <8f886f13-6550-4322-95be-93244ae61045@phunq.net> <55545C2F.8040207@phunq.net> <20150519140045.GA16313@quack.suse.cz> <555B8C79.4090909@phunq.net> <20150520144429.GA17783@quack.suse.cz> <555CB4B6.8050305@phunq.net> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Cc: linux-fsdevel@vger.kernel.org, tux3@tux3.org, linux-kernel@vger.kernel.org, OGAWA Hirofumi To: Daniel Phillips , Jan Kara , David Lang Return-path: In-Reply-To: <555CB4B6.8050305@phunq.net> List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: tux3-bounces@phunq.net Sender: "Tux3" List-Id: linux-fsdevel.vger.kernel.org On 05/20/2015 12:22 PM, Daniel Phillips wrote: > On 05/20/2015 07:44 AM, Jan Kara wrote: >> On Tue 19-05-15 13:33:31, David Lang wrote: >> Yeah, that's what I meant. If you create a function which manipulates >> page cache, you better make it work with other functions manipulating page >> cache. Otherwise it's a landmine waiting to be tripped by some unsuspecting >> developer. Sure you can document all the conditions under which the >> function is safe to use but a function that has several paragraphs in front >> of it explaning when it is safe to use isn't very good API... > > Violent agreement, of course. To put it in concrete terms, each of > the page fork support functions must be examined and determined > sane. They are: > > * cow_replace_page_cache > * cow_delete_from_page_cache > * cow_clone_page > * page_cow_one > * page_cow_file > > Would it be useful to drill down into those, starting from the top > of the list? How do these interact with other page cache functions, like find_get_page() ? How does tux3 prevent a user of find_get_page() from reading from or writing into the pre-COW page, instead of the current page? -- All rights reversed