Subject: + lib-scatterlistc-dont-flush_kernel_dcache_page-on-slab-page.patch added to -mm tree
To: ming.lei@xxxxxxxxxxxxx,JBottomley@xxxxxxxxxxxxx,aaro.koskinen@xxxxxx,axboe@xxxxxxxxx,catalin.marinas@xxxxxxx,fujita.tomonori@xxxxxxxxxxxxx,gmbnomis@xxxxxxxxx,linux@xxxxxxxxxxxxxxxx,stable@xxxxxxxxxxxxxxx,tj@xxxxxxxxxx,will.deacon@xxxxxxx
From: akpm@xxxxxxxxxxxxxxxxxxxx
Date: Thu, 31 Oct 2013 15:27:54 -0700
The patch titled
Subject: lib/scatterlist.c: don't flush_kernel_dcache_page on slab page
has been added to the -mm tree. Its filename is
lib-scatterlistc-dont-flush_kernel_dcache_page-on-slab-page.patch
This patch should soon appear at
http://ozlabs.org/~akpm/mmots/broken-out/lib-scatterlistc-dont-flush_kernel_dcache_page-on-slab-page.patch
and later at
http://ozlabs.org/~akpm/mmotm/broken-out/lib-scatterlistc-dont-flush_kernel_dcache_page-on-slab-page.patch
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------------------------------------------------------
From: Ming Lei <ming.lei@xxxxxxxxxxxxx>
Subject: lib/scatterlist.c: don't flush_kernel_dcache_page on slab page
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().
Signed-off-by: Ming Lei <ming.lei@xxxxxxxxxxxxx>
Reported-by: Aaro Koskinen <aaro.koskinen@xxxxxx>
Tested-by: Simon Baatz <gmbnomis@xxxxxxxxx>
Cc: Russell King - ARM Linux <linux@xxxxxxxxxxxxxxxx>
Cc: Will Deacon <will.deacon@xxxxxxx>
Cc: Aaro Koskinen <aaro.koskinen@xxxxxx>
Acked-by: Catalin Marinas <catalin.marinas@xxxxxxx>
Cc: FUJITA Tomonori <fujita.tomonori@xxxxxxxxxxxxx>
Cc: Tejun Heo <tj@xxxxxxxxxx>
Cc: "James E.J. Bottomley" <JBottomley@xxxxxxxxxxxxx>
Cc: Jens Axboe <axboe@xxxxxxxxx>
Cc: <stable@xxxxxxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
lib/scatterlist.c | 3 ++-
1 file changed, 2 insertions(+), 1 deletion(-)
diff -puN lib/scatterlist.c~lib-scatterlistc-dont-flush_kernel_dcache_page-on-slab-page lib/scatterlist.c
--- a/lib/scatterlist.c~lib-scatterlistc-dont-flush_kernel_dcache_page-on-slab-page
+++ a/lib/scatterlist.c
@@ -577,7 +577,8 @@ void sg_miter_stop(struct sg_mapping_ite
miter->__offset += miter->consumed;
miter->__remaining -= miter->consumed;
- if (miter->__flags & SG_MITER_TO_SG)
+ if ((miter->__flags & SG_MITER_TO_SG) &&
+ !PageSlab(miter->page))
flush_kernel_dcache_page(miter->page);
if (miter->__flags & SG_MITER_ATOMIC) {
_
Patches currently in -mm which might be from ming.lei@xxxxxxxxxxxxx are
lib-scatterlistc-dont-flush_kernel_dcache_page-on-slab-page.patch
linux-next.patch
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