From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail138.messagelabs.com (mail138.messagelabs.com [216.82.249.35]) by kanga.kvack.org (Postfix) with SMTP id 8637D6B008A for ; Tue, 24 Nov 2009 05:46:32 -0500 (EST) Date: Tue, 24 Nov 2009 19:46:25 +0900 (JST) From: KOSAKI Motohiro Subject: Re: [PATCH 4/7] nandsim: Don't use PF_MEMALLOC In-Reply-To: <4B0AEA33.3010306@nokia.com> References: <1258988417.18407.44.camel@localhost> <4B0AEA33.3010306@nokia.com> Message-Id: <20091124194532.AFC2.A69D9226@jp.fujitsu.com> MIME-Version: 1.0 Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: 8bit Sender: owner-linux-mm@kvack.org To: Adrian Hunter Cc: kosaki.motohiro@jp.fujitsu.com, "Bityutskiy Artem (Nokia-D/Helsinki)" , LKML , linux-mm , Andrew Morton , David Woodhouse , "linux-mtd@lists.infradead.org" List-ID: Hi Thank you for this useful comments. > > I vaguely remember Adrian (CCed) did this on purpose. This is for the > > case when nandsim emulates NAND flash on top of a file. So there are 2 > > file-systems involved: one sits on top of nandsim (e.g. UBIFS) and the > > other owns the file which nandsim uses (e.g., ext3). > > > > And I really cannot remember off the top of my head why he needed > > PF_MEMALLOC, but I think Adrian wanted to prevent the direct reclaim > > path to re-enter, say UBIFS, and cause deadlock. But I'd thing that all > > the allocations in vfs_read()/vfs_write() should be GFP_NOFS, so that > > should not be a probelm? > > > > Yes it needs PF_MEMALLOC to prevent deadlock because there can be a > file system on top of nandsim which, in this case, is on top of another > file system. > > I do not see how mempools will help here. > > Please offer an alternative solution. I have few questions. Can you please explain more detail? Another stackable filesystam (e.g. ecryptfs) don't have such problem. Why nandsim have its issue? What lock cause deadlock? -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org