From mboxrd@z Thu Jan 1 00:00:00 1970 From: David Howells Subject: Re: [PATCH 06/43] FS-Cache: Recruit a couple of page flags for cache management [ver #46] Date: Thu, 02 Apr 2009 15:36:12 +0100 Message-ID: <5198.1238682972@redhat.com> References: <200904030055.26668.nickpiggin@yahoo.com.au> <20090401230321.28177.12010.stgit@warthog.procyon.org.uk> <20090401230352.28177.65878.stgit@warthog.procyon.org.uk> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Cc: dhowells@redhat.com, linux-fsdevel@vger.kernel.org, nfsv4@linux-nfs.org, viro@zeniv.linux.org.uk, linux-kernel@vger.kernel.org To: Nick Piggin Return-path: In-Reply-To: <200904030055.26668.nickpiggin@yahoo.com.au> List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: nfsv4-bounces@linux-nfs.org Errors-To: nfsv4-bounces@linux-nfs.org List-Id: linux-fsdevel.vger.kernel.org Nick Piggin wrote: > 1) PG_mappedtodisk is basically PG_owner_priv_2. Please alias that and > use it? Then at least we're down to 1 extra flag. > 2) Why do you need another PG_private? PG_private for pagecache means > that it should call into the filesystem when it needs to handle fs data > attached to the page, right? So PG_private_2 doesn't really make sense > in that respect. Won't that either break fs/buffer.c and fs/mpage.c or preclude the use of FS-Cache with block-based filesystems that use the standard buffer wangling routines? As I've previously stated, I want to be able to make ISO9660 use FS-Cache. That rules out use of PG_mappedtodisk and PG_private for anything FS-Cache related. We can actually reclaim PG_private, I think. There are patches to do that. At the very least, we can probably reclaim the std buffering code's use of it. If anything, avoiding the need for PG_fscache_write is probably easier - just more memory intensive and slower. I could build a second radix tree for each inode that kept track of which pages from that inode FS-Cache knows about, and use the status bits in that node to keep track of what pages are being written out to the cache. We still need a way of triggering the page invalidation callbacks for in-use pages, however. PG_private, as I've said, is not currently a viable option. David