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Date: Tue, 26 Jun 2007 12:42:27 +1000 From: Nick Piggin <nickpiggin@...oo.com.au> To: Chris Mason <chris.mason@...cle.com> CC: Nick Piggin <npiggin@...e.de>, Linux Kernel Mailing List <linux-kernel@...r.kernel.org>, Linux Memory Management List <linux-mm@...ck.org>, linux-fsdevel@...r.kernel.org Subject: Re: [patch 1/3] add the fsblock layer Chris Mason wrote: > On Sun, Jun 24, 2007 at 03:46:13AM +0200, Nick Piggin wrote: > >>Rewrite the buffer layer. > > > Overall, I like the basic concepts, but it is hard to track the locking > rules. Could you please write them up? Yeah I will do that. Thanks for taking a look. One thing I am thinking about is to get rid of the unmap_underlying_metadata calls from the generic code. I found they were required for minix to prevent corruption, however I don't know exactly what metadata is interfering here (maybe it is indirect blocks or something?). Anyway, I think I will make it a requirement that the filesystem has to already handle this before returning a newly allocated block -- they can probably do it more efficiently and we avoid the extra work on every block allocation. > I like the way you split out the assoc_buffers from the main fsblock > code, but the list setup is still something of a wart. It also provides > poor ordering of blocks for writeback. Yeah, I didn't know how much effort to put in here because I don't know whether modern filesystems are going to need to implement their own management of this stuff or not. I haven't actually instrumented this in something like ext2 to see how much IO comes from the assoc buffers... > I think it makes sense to replace the assoc_buffers list head with a > radix tree sorted by block number. mark_buffer_dirty_inode would up the > reference count and put it into the radix, the various flushing routines > would walk the radix etc. > > If you wanted to be able to drop the reference count once the block was > written you could have a back pointer to the appropriate inode. I was actually thinking about a radix-tree :) One annoyance is that unsigned long != sector_t :P rbtree would probably be OK. -- SUSE Labs, Novell Inc. - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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