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From: Christoph Hellwig <hch@lst.de>
To: Peng Tao <bergwolf@gmail.com>
Cc: Christoph Hellwig <hch@lst.de>,
	Trond Myklebust <trond.myklebust@primarydata.com>,
	linuxnfs <linux-nfs@vger.kernel.org>,
	"faibish, sorin" <faibish_sorin@emc.com>
Subject: Re: [PATCH 08/17] pnfs/blocklayout: reject pnfs blocksize larger than page size
Date: Thu, 7 Aug 2014 13:25:37 +0200	[thread overview]
Message-ID: <20140807112537.GA3437@lst.de> (raw)
In-Reply-To: <CA+a=Yy42e46zA+X-VQQj9RAzZ4T+A7dOOrjUMVONsh8Pt8QdcQ@mail.gmail.com>

On Thu, Aug 07, 2014 at 06:43:14PM +0800, Peng Tao wrote:
> So this kills EMC server support.

Given the state the code  claiming support for any server is a large
exaggeration..

> Can you please share what kind of
> badly deadlock you saw with large block size support?

The read-modify write code (which I'll remove later) can lock arbitary
numbers of additional pages from the writeback back code without doing
a trylock, which is required for doing this in page writeback.  Note
that it's not a deadlock, but I can also trivіally corrupt data in
those pages as it doesn't lock against them, you just need a race
window where it's modified after writeback has been started for a large
extents, which isn't too hard to hit with tools like fsstress.


  reply	other threads:[~2014-08-07 11:25 UTC|newest]

Thread overview: 38+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2014-08-07  7:23 pnfs block layout driver fixes Christoph Hellwig
2014-08-07  7:23 ` [PATCH 01/17] nfs: cap request size to fit a kmalloced page array Christoph Hellwig
2014-08-07  7:23 ` [PATCH 02/17] pnfs: do not pass uninitialized lsegs to ->free_lseg Christoph Hellwig
2014-08-07  7:23 ` [PATCH 03/17] pnfs: force a layout commit when encountering busy segments during recall Christoph Hellwig
2014-08-07  7:23 ` [PATCH 04/17] pnfs: don't check sequence on new stateids in layoutget Christoph Hellwig
2014-08-07  7:23 ` [PATCH 05/17] pnfs: add flag to force read-modify-write in ->write_begin Christoph Hellwig
2014-08-07  7:23 ` [PATCH 06/17] pnfs: add return_range method Christoph Hellwig
2014-08-07  7:23 ` [PATCH 07/17] pnfs: allow splicing pre-encoded pages into the layoutcommit args Christoph Hellwig
2014-08-07  7:23 ` [PATCH 08/17] pnfs/blocklayout: reject pnfs blocksize larger than page size Christoph Hellwig
2014-08-07 10:43   ` Peng Tao
2014-08-07 11:25     ` Christoph Hellwig [this message]
2014-08-07 11:51       ` Peng Tao
2014-08-07 12:10         ` Christoph Hellwig
2014-08-07 13:43           ` Peng Tao
2014-08-07 16:20             ` Christoph Hellwig
2014-08-08 10:28               ` Peng Tao
2014-08-07 12:56         ` faibish, sorin
2014-08-07 13:45           ` Peng Tao
2014-08-07 16:10           ` Christoph Hellwig
2014-08-07 16:18             ` faibish, sorin
2014-08-07 13:13       ` Steve Dickson
2014-08-07 13:17         ` Steve Dickson
2014-08-07  7:23 ` [PATCH 09/17] pnfs/blocklayout: improve GETDEVICEINFO error reporting Christoph Hellwig
2014-08-07  7:23 ` [PATCH 10/17] pnfs/blocklayout: plug block queues Christoph Hellwig
2014-08-07  7:23 ` [PATCH 11/17] pnfs/blocklayout: correctly decrement extent length Christoph Hellwig
2014-08-07  7:23 ` [PATCH 12/17] pnfs/blocklayout: remove read-modify-write handling in bl_write_pagelist Christoph Hellwig
2014-08-07  7:23 ` [PATCH 13/17] pnfs/blocklayout: don't set pages uptodate Christoph Hellwig
2014-08-07  7:23 ` [PATCH 14/17] pnfs/blocklayout: rewrite extent tracking Christoph Hellwig
2014-08-07  7:23 ` [PATCH 15/17] pnfs/blocklayout: implement the return_range method Christoph Hellwig
2014-08-07  7:23 ` [PATCH 16/17] pnfs/blocklayout: return layouts on setattr Christoph Hellwig
2014-08-07  7:23 ` [PATCH 17/17] pnfs/blocklayout: allocate separate pages for the layoutcommit payload Christoph Hellwig
2014-08-07 11:05   ` Peng Tao
2014-08-07 11:27     ` Christoph Hellwig
2014-08-07 11:57       ` Peng Tao
2014-08-20 18:43 ` pnfs block layout driver fixes Jeff Layton
2014-08-20 22:14   ` Christoph Hellwig
2014-09-07 15:39 ` Christoph Hellwig
2014-09-07 16:44   ` Trond Myklebust

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