From mboxrd@z Thu Jan 1 00:00:00 1970 Date: Sat, 31 May 2003 16:48:16 -0700 From: "Paul E. McKenney" Subject: Re: Always passing mm and vma down (was: [RFC][PATCH] Convert do_no_page() to a hook to avoid DFS race) Message-ID: <20030531234816.GB1408@us.ibm.com> Reply-To: paulmck@us.ibm.com References: <20030530164150.A26766@us.ibm.com> <20030531104617.J672@nightmaster.csn.tu-chemnitz.de> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20030531104617.J672@nightmaster.csn.tu-chemnitz.de> Sender: owner-linux-mm@kvack.org Return-Path: To: Ingo Oeser Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org, akpm@digeo.com, hch@infradead.org List-ID: On Sat, May 31, 2003 at 10:46:18AM +0200, Ingo Oeser wrote: > On Fri, May 30, 2003 at 04:41:50PM -0700, Paul E. McKenney wrote: > > -struct page * > > -ia32_install_shared_page (struct vm_area_struct *vma, unsigned long address, int no_share) > > +int > > +ia32_install_shared_page (struct mm_struct *mm, struct vm_area_struct *vma, unsigned long address, int write_access, pmd_t *pmd) > > Why do we always pass mm and vma down, even if vma->vm_mm > contains the mm, where the vma belongs to? Is the connection > between a vma and its mm also protected by the mmap_sem? > > Is this really necessary or an oversight and we waste a lot of > stack in a lot of places? > > If we just need it for accounting: We need current->mm, if we > need it to locate the next vma relatively to this vma, vma->vm_mm > is the one. Interesting point. The original do_no_page() API does this as well: static int do_no_page(struct mm_struct *mm, struct vm_area_struct *vma, unsigned long address, int write_access, pte_t *page_table, pmd_t *pmd) As does do_anonymous_page(). I assumed that there were corner cases where this one-to-one correspondence did not exist, but must confess that I did not go looking for them. Or is this a performance issue, avoiding a dereference and possible cache miss? Thanx, Paul -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: aart@kvack.org