From mboxrd@z Thu Jan 1 00:00:00 1970 From: Nick Piggin Subject: Re: [RFC][PATCH] block: Isolate the buffer cache in it's own mappings. Date: Thu, 18 Oct 2007 15:10:48 +1000 References: <200710151028.34407.borntraeger@de.ibm.com> <1192665785.15717.34.camel@think.oraclecorp.com> In-Reply-To: MIME-Version: 1.0 Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: 7bit Content-Disposition: inline Message-Id: <200710181510.48382.nickpiggin@yahoo.com.au> Sender: owner-linux-mm@kvack.org Return-Path: To: "Eric W. Biederman" Cc: Chris Mason , Christian Borntraeger , Andrew Morton , linux-mm@kvack.org, linux-kernel@vger.kernel.org, Martin Schwidefsky , Theodore Ts'o , stable@kernel.org List-ID: On Thursday 18 October 2007 13:59, Eric W. Biederman wrote: > If filesystems care at all they want absolute control over the buffer > cache. Controlling which buffers are dirty and when. Because we > keep the buffer cache in the page cache for the block device we have > not quite been giving filesystems that control leading to really weird > bugs. Mmm. Like I said, when a live filesystem is mounted on a bdev, it isn't like you want userspace to go dancing around on it without knowing exactly what it is doing. The kernel more or less does the right thing here with respect to the *state* of the data[*] (that is, buffer heads and pagecache). It's when you actually start changing the data itself around is when you'll blow up the filesystem. [*] The ramdisk code is simply buggy, right? (and not the buffer cache) The idea of your patch in theory is OK, but Andrew raises valid points about potential coherency problems, I think. -- 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