Messages in this thread | | | Date | Sat, 5 Apr 2008 10:29:25 +0900 | From | "Kyungmin Park" <> | Subject | Re: [PATCH] jffs2 summary allocation |
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On Sat, Apr 5, 2008 at 10:11 AM, Josh Boyer <jwboyer@gmail.com> wrote: > On Fri, 2008-04-04 at 16:58 -0700, David Brownell wrote: > > On Friday 04 April 2008, Josh Boyer wrote: > > > > > > > ... This means specifically that you may _not_ use the > > > > memory/addresses returned from vmalloc() for DMA. ... > > > > > > > > So I'm rather surprised to see *ANY* kernel code trying to do > > > > that. That rule has been in effect for many, many years now. > > > > > > I don't think it was intentional. You're going through several layers > > > here: > > > > > > JFFS2 -> mtd parts -> mtd dataflash -> atmel_spi. > > > > > > Typically MTD drivers aren't doing DMAs to flash and JFFS2 has no idea > > > which particular chip driver is being used because it's abstracted by > > > MTD. > > > > That's true ... although I can imagine using DMA to > > avoid dcache trashing if its setup cost is low enough, > > with either NAND or NOR chips. > > > > Still: in this context vmalloc() is wrong. > > Agreed. One issue is that the summary code allocates a buffer that > equals the eraseblock size of the underlying MTD device. For larger > NAND chips, that may be up to 256KiB. I believe this is within the > allowable kmalloc size for most architectures these days, but the > summary code is 3 years old and was likely expecting a smaller limit. > And there is always the question on whether finding that much contiguous > memory will be an issue.
In MLC chips it goes up to 512KiB. It means it can't allocate the eraseblock size memory with kmalloc(). In ARM environment I can't see the 256KiB or more memory allocation with kmalloc(). So I now changed the kmalloc eraseblock to vmalloc at both jffs2 and mtd-utils.
Thank you, Kyungmin Park
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