| Message ID | 1423645301-709-1-git-send-email-acourbot@nvidia.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
On Wed, Feb 11, 2015 at 09:01:41AM +0000, Alexandre Courbot wrote: > There doesn't seem to be any valid reason to allocate the pages array > with the same flags as the buffer itself. Doing so can eventually lead > to the following safeguard in mm/slab.c to be hit: > > BUG_ON(flags & GFP_SLAB_BUG_MASK); nit: I can't actually spot this BUG_ON in the kernel. > This happens when buffers are allocated with __GFP_DMA32 or > __GFP_HIGHMEM. > > Fix this by allocating the pages array with GFP_KERNEL to follow what is > done elsewhere in this file. Using GFP_KERNEL in __iommu_alloc_buffer() > is safe because atomic allocations are handled by __iommu_alloc_atomic(). > > Signed-off-by: Alexandre Courbot <acourbot@nvidia.com> > Cc: Arnd Bergmann <arnd@arndb.de> > Cc: Marek Szyprowski <m.szyprowski@samsung.com> > Cc: Russell King <linux@arm.linux.org.uk> > Acked-by: Marek Szyprowski <m.szyprowski@samsung.com> > --- > arch/arm/mm/dma-mapping.c | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > diff --git a/arch/arm/mm/dma-mapping.c b/arch/arm/mm/dma-mapping.c > index 903dba0..170a116 100644 > --- a/arch/arm/mm/dma-mapping.c > +++ b/arch/arm/mm/dma-mapping.c > @@ -1106,7 +1106,7 @@ static struct page **__iommu_alloc_buffer(struct device *dev, size_t size, > int i = 0; > > if (array_size <= PAGE_SIZE) > - pages = kzalloc(array_size, gfp); > + pages = kzalloc(array_size, GFP_KERNEL); > else > pages = vzalloc(array_size); > if (!pages) > -- > 2.3.0 Looks sensible to me: Acked-by: Will Deacon <will.deacon@arm.com> Will
On 02/13/2015 12:32 PM, Will Deacon wrote: > On Wed, Feb 11, 2015 at 09:01:41AM +0000, Alexandre Courbot wrote: >> There doesn't seem to be any valid reason to allocate the pages array >> with the same flags as the buffer itself. Doing so can eventually lead >> to the following safeguard in mm/slab.c to be hit: >> >> BUG_ON(flags & GFP_SLAB_BUG_MASK); > > nit: I can't actually spot this BUG_ON in the kernel. I have been trying to push this patch for so long that the line in question changed in the meantime. :) It is now if (unlikely(flags & GFP_SLAB_BUG_MASK)) { pr_emerg("gfp: %u\n", flags & GFP_SLAB_BUG_MASK); BUG(); } in cache_grow, line 2593 of mm/slab.c. > >> This happens when buffers are allocated with __GFP_DMA32 or >> __GFP_HIGHMEM. >> >> Fix this by allocating the pages array with GFP_KERNEL to follow what is >> done elsewhere in this file. Using GFP_KERNEL in __iommu_alloc_buffer() >> is safe because atomic allocations are handled by __iommu_alloc_atomic(). >> >> Signed-off-by: Alexandre Courbot <acourbot@nvidia.com> >> Cc: Arnd Bergmann <arnd@arndb.de> >> Cc: Marek Szyprowski <m.szyprowski@samsung.com> >> Cc: Russell King <linux@arm.linux.org.uk> >> Acked-by: Marek Szyprowski <m.szyprowski@samsung.com> >> --- >> arch/arm/mm/dma-mapping.c | 2 +- >> 1 file changed, 1 insertion(+), 1 deletion(-) >> >> diff --git a/arch/arm/mm/dma-mapping.c b/arch/arm/mm/dma-mapping.c >> index 903dba0..170a116 100644 >> --- a/arch/arm/mm/dma-mapping.c >> +++ b/arch/arm/mm/dma-mapping.c >> @@ -1106,7 +1106,7 @@ static struct page **__iommu_alloc_buffer(struct device *dev, size_t size, >> int i = 0; >> >> if (array_size <= PAGE_SIZE) >> - pages = kzalloc(array_size, gfp); >> + pages = kzalloc(array_size, GFP_KERNEL); >> else >> pages = vzalloc(array_size); >> if (!pages) >> -- >> 2.3.0 > > Looks sensible to me: > > Acked-by: Will Deacon <will.deacon@arm.com> Thanks! I will amend the commit message and resend.
diff --git a/arch/arm/mm/dma-mapping.c b/arch/arm/mm/dma-mapping.c index 903dba0..170a116 100644 --- a/arch/arm/mm/dma-mapping.c +++ b/arch/arm/mm/dma-mapping.c @@ -1106,7 +1106,7 @@ static struct page **__iommu_alloc_buffer(struct device *dev, size_t size, int i = 0; if (array_size <= PAGE_SIZE) - pages = kzalloc(array_size, gfp); + pages = kzalloc(array_size, GFP_KERNEL); else pages = vzalloc(array_size); if (!pages)