From mboxrd@z Thu Jan 1 00:00:00 1970 Date: Sat, 16 Feb 2008 11:31:09 -0800 (PST) From: Christoph Lameter Subject: Re: [patch 1/6] mmu_notifier: Core code In-Reply-To: <20080216025803.40d8ccbc.akpm@linux-foundation.org> Message-ID: References: <20080215064859.384203497@sgi.com> <20080215064932.371510599@sgi.com> <20080215193719.262c03a1.akpm@linux-foundation.org> <47B6BDDF.90502@inria.fr> <20080216025803.40d8ccbc.akpm@linux-foundation.org> MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Sender: owner-linux-mm@kvack.org Return-Path: To: Andrew Morton Cc: Brice Goglin , Andrea Arcangeli , linux-kernel@vger.kernel.org, linux-mm@kvack.org List-ID: On Sat, 16 Feb 2008, Andrew Morton wrote: > "looks good" maybe. But it's in the details where I fear this will come > unstuck. The likelihood that some callbacks really will want to be able to > block in places where this interface doesn't permit that - either to wait > for IO to complete or to wait for other threads to clear critical regions. We can get the invalidate_range to always be called without spinlocks if we deal with the case of the inode_mmap_lock being held in truncate case. If you always want to be able to sleep then we could drop the invalidate_page() that is called while pte locks held and require the use of a device driver rmap? > >From that POV it doesn't look like a sufficiently general and useful > design. Looks like it was grafted onto the current VM implementation in a > way which just about suits two particular clients if they try hard enough. You missed KVM. We did the best we could being as least invasive as possible. > Which is all perfectly understandable - it would be hard to rework core MM > to be able to make this interface more general. But I do think it's > half-baked and there is a decent risk that future (or present) code which > _could_ use something like this won't be able to use this one, and will > continue to futz with mlock, page-pinning, etc. > > Not that I know what the fix to that is.. You do not see a chance of this being okay if we adopt the two measures that I mentioned above? -- 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: email@kvack.org