Messages in this thread | | | Date | Thu, 31 Oct 2013 22:44:31 +0000 | From | Russell King - ARM Linux <> | Subject | Re: [PATCH] lib/scatterlist.c: don't flush_kernel_dcache_page on slab page |
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On Thu, Oct 31, 2013 at 03:27:45PM -0700, Andrew Morton wrote: > On Tue, 29 Oct 2013 00:20:05 +0800 Ming Lei <ming.lei@canonical.com> wrote: > > > Commit b1adaf65ba03([SCSI] block: add sg buffer copy helper functions) > > introduces two sg buffer copy helpers, and calls flush_kernel_dcache_page() > > on pages in SG list after these pages are written to. > > > > Unfortunately, the commit may introduce a potential bug: > > > > - Before sending some SCSI commands, kmalloc() buffer may be > > passed to block layper, so flush_kernel_dcache_page() can > > see a slab page finally > > > > - According to cachetlb.txt, flush_kernel_dcache_page() is > > only called on "a user page", which surely can't be a slab page. > > > > - ARCH's implementation of flush_kernel_dcache_page() may > > use page mapping information to do optimization so page_mapping() > > will see the slab page, then VM_BUG_ON() is triggered. > > > > Aaro Koskinen reported the bug on ARM/kirkwood when DEBUG_VM is enabled, > > and this patch fixes the bug by adding test of '!PageSlab(miter->page)' > > before calling flush_kernel_dcache_page(). > > We should work out which kernel(s) need this patch. b1adaf65ba03 was > merged in 2008, so presumably some more recent patch has exposed the > problem, but I don't know what one that was. > > Help me out here?
1bc39742aab0 (ARM: 7755/1: handle user space mapped pages in flush_kernel_dcache_page) in June 2013, which according to git describe is:
v3.10-rc4-9-g1bc39742aab0
Presumably that means v3.10+ need it.
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