Commit 3d77b50c authored by Ming Lei's avatar Ming Lei Committed by Linus Torvalds

lib/scatterlist.c: don't flush_kernel_dcache_page on slab page

Commit b1adaf65 ("[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

 - 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: default avatarMing Lei <>
Reported-by: default avatarAaro Koskinen <>
Tested-by: default avatarSimon Baatz <>
Cc: Russell King - ARM Linux <>
Cc: Will Deacon <>
Cc: Aaro Koskinen <>
Acked-by: default avatarCatalin Marinas <>
Cc: FUJITA Tomonori <>
Cc: Tejun Heo <>
Cc: "James E.J. Bottomley" <>
Cc: Jens Axboe <>
Cc: <>	[3.2+]
Signed-off-by: default avatarAndrew Morton <>
Signed-off-by: default avatarLinus Torvalds <>
parent 696ac172
......@@ -577,7 +577,8 @@ void sg_miter_stop(struct sg_mapping_iter *miter)
miter->__offset += miter->consumed;
miter->__remaining -= miter->consumed;
if (miter->__flags & SG_MITER_TO_SG)
if ((miter->__flags & SG_MITER_TO_SG) &&
if (miter->__flags & SG_MITER_ATOMIC) {
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