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Date: Tue, 24 Nov 2009 19:46:25 +0900 (JST) From: KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com> To: Adrian Hunter <adrian.hunter@...ia.com> Cc: kosaki.motohiro@...fujitsu.com, "Bityutskiy Artem (Nokia-D/Helsinki)" <Artem.Bityutskiy@...ia.com>, LKML <linux-kernel@...r.kernel.org>, linux-mm <linux-mm@...ck.org>, Andrew Morton <akpm@...ux-foundation.org>, David Woodhouse <David.Woodhouse@...el.com>, "linux-mtd@...ts.infradead.org" <linux-mtd@...ts.infradead.org> Subject: Re: [PATCH 4/7] nandsim: Don't use PF_MEMALLOC 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 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/
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