From: "Stephen C. Tweedie" <sct@dcs.ed.ac.uk>
To: "Eric W. Biederman" <ebiederm+eric@npwt.net>
Cc: "Stephen C. Tweedie" <sct@dcs.ed.ac.uk>,
Hans Reiser <reiser@ricochet.net>,
Shawn Leas <sleas@ixion.honeywell.com>,
Reiserfs <reiserfs@devlinux.com>,
Ken Tetrick <ktetrick@ixion.honeywell.com>,
linux-mm@kvack.org
Subject: Re: (reiserfs) Re: More on Re: (reiserfs) Reiserfs and ext2fs (was Re: (reiserfs) Sum Benchmarks (these look typical?))
Date: Tue, 30 Jun 1998 17:10:46 +0100 [thread overview]
Message-ID: <199806301610.RAA00957@dax.dcs.ed.ac.uk> (raw)
In-Reply-To: <m1u354dlna.fsf@flinx.npwt.net>
Hi,
On 29 Jun 1998 14:59:37 -0500, ebiederm+eric@npwt.net (Eric
W. Biederman) said:
> There are two problems I see.
> 1) A DMA controller actively access the same memory the CPU is
> accessing could be a problem. Recall video flicker on old video
> cards.
Shouldn't be a problem.
> 2) More importantly the cpu writes to the _cache_, and the DMA
> controller reads from the RAM. I don't see any consistency garnatees
> there. We may be able solve these problems on a per architecture or
> device basis however.
Again, not important. If we ever modify a page which is already being
written out to a device, then we mark that page dirty. On write, we
mark it clean (but locked) _before_ starting the IO, not after. So, if
there is ever an overlap of a filesystem/mmap write with an IO to disk,
we will always schedule another IO later to clean the re-dirtied
buffers.
--Stephen
next prev parent reply other threads:[~1998-06-30 19:09 UTC|newest]
Thread overview: 11+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <Pine.HPP.3.96.980617035608.29950A-100000@ixion.honeywell.com>
[not found] ` <199806221138.MAA00852@dax.dcs.ed.ac.uk>
[not found] ` <358F4FBE.821B333C@ricochet.net>
[not found] ` <m11zsgrvnf.fsf@flinx.npwt.net>
[not found] ` <199806241154.MAA03544@dax.dcs.ed.ac.uk>
[not found] ` <m11zse6ecw.fsf@flinx.npwt.net>
1998-06-25 11:00 ` Stephen C. Tweedie
1998-06-26 15:56 ` Eric W. Biederman
1998-06-29 10:35 ` Stephen C. Tweedie
1998-06-29 19:59 ` Eric W. Biederman
1998-06-30 16:10 ` Stephen C. Tweedie [this message]
1998-07-01 0:17 ` Eric W. Biederman
1998-07-01 9:12 ` Stephen C. Tweedie
1998-07-01 12:45 ` Eric W. Biederman
1998-07-01 13:11 ` Eric W. Biederman
1998-07-01 20:07 ` Stephen C. Tweedie
1998-07-02 15:17 ` Eric W. Biederman
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