linux-kernel - Re: [patch 1/3] add the fsblock layer

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <20070625122906.GB12446@think.oraclecorp.com>
Date:	Mon, 25 Jun 2007 08:29:06 -0400
From:	Chris Mason <chris.mason@...cle.com>
To:	Nick Piggin <nickpiggin@...oo.com.au>
Cc:	Neil Brown <neilb@...e.de>, 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

On Mon, Jun 25, 2007 at 05:41:58PM +1000, Nick Piggin wrote:
> Neil Brown wrote:
> >On Sunday June 24, npiggin@...e.de wrote:
> >
> >>
> >>+#define PG_blocks		20	/* Page has block mappings */
> >>+
> >
> >
> >I've only had a very quick look, but this line looks *very* wrong.
> >You should be using PG_private.
> >
> >There should never be any confusion about whether ->private has
> >buffers or blocks attached as the only routines that ever look in
> >->private are address_space operations  (or should be.  I think 'NULL'
> >is sometimes special cased, as in try_to_release_page.  It would be
> >good to do some preliminary work and tidy all that up).
> 
> There is a lot of confusion, actually :)
> But as you see in the patch, I added a couple more aops APIs, and
> am working toward decoupling it as much as possible. It's pretty
> close after the fsblock patch... however:
> 
> 
> >Why do you think you need PG_blocks?
> 
> Block device pagecache (buffer cache) has to be able to accept
> attachment of either buffers or blocks for filesystem metadata,
> and call into either buffer.c or fsblock.c based on that.
> 
> If the page flag is really important, we can do some awful hack
> like assuming the first long of the private data is flags, and
> those flags will tell us whether the structure is a buffer_head
> or fsblock ;) But for now it is just easier to use a page flag.

The block device pagecache isn't special, and certainly isn't that much
code.  I would suggest keeping it buffer head specific and making a
second variant that does only fsblocks.  This is mostly to keep the
semantics of PagePrivate sane, lets not fuzz the line.

-chris

-
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/