From: Christoph Hellwig <hch@lst.de>
To: Tejun Heo <tj@kernel.org>
Cc: Christoph Hellwig <hch@lst.de>, Ilya Dryomov <idryomov@gmail.com>,
Alexander Viro <viro@zeniv.linux.org.uk>,
linux-fsdevel@vger.kernel.org
Subject: Re: [PATCH] block: detach bdev inode from its wb in __blkdev_put()
Date: Tue, 24 Nov 2015 08:54:57 +0100 [thread overview]
Message-ID: <20151124075457.GC29572@lst.de> (raw)
In-Reply-To: <20151123153552.GA3049@mtj.duckdns.org>
On Mon, Nov 23, 2015 at 10:35:52AM -0500, Tejun Heo wrote:
> Hello, Christoph.
>
> On Sun, Nov 22, 2015 at 04:02:16PM +0100, Christoph Hellwig wrote:
> > The right fix is to never point from the inode to a BDI. I fixed this
> > with a lot of effort, and the BDI writeback series put it back a little
> > later. We need to revert that damage (not neseccarily literally, but the
> > effect).
>
> Can you please explain a bit more why inode pointing to its associated
> bdi_writeback is a bad idea? The only alternative would be recording
> a key and looking up each time. We sure can do that but I don't get
> why we would want to.
Because the writeback context really is a per-super block concept
(except for the magic block device inodes). Having another pointer
pointer in the inode (or address_space back then) lead to all kinds
of confusing bugs and life time issues, nevermind massively bloating the
inode for no reason. But then again bloating the inode has been rather
en vogue lately anyway.
next prev parent reply other threads:[~2015-11-24 7:54 UTC|newest]
Thread overview: 12+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-11-20 21:22 [PATCH] block: detach bdev inode from its wb in __blkdev_put() Ilya Dryomov
2015-11-20 21:23 ` Tejun Heo
2015-11-22 15:02 ` Christoph Hellwig
2015-11-23 15:35 ` Tejun Heo
2015-11-24 7:54 ` Christoph Hellwig [this message]
2015-11-24 14:00 ` Tejun Heo
2015-11-30 7:20 ` Raghavendra K T
2015-11-30 10:54 ` Ilya Dryomov
2015-12-04 14:07 ` Ilya Dryomov
2015-12-04 17:44 ` Jens Axboe
2015-12-04 17:55 ` Ilya Dryomov
2015-12-04 18:02 ` Jens Axboe
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