Messages in this thread | | | Date | Thu, 14 May 2015 16:29:44 +1000 | From | Alexey Kardashevskiy <> | Subject | Re: [PATCH kernel v10 05/34] powerpc/iommu: Always release iommu_table in iommu_free_table() |
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On 05/14/2015 12:53 PM, Alex Williamson wrote: > On Thu, 2015-05-14 at 12:34 +1000, Alexey Kardashevskiy wrote: >> On 05/14/2015 09:27 AM, Gavin Shan wrote: >>> On Wed, May 13, 2015 at 02:51:36PM +0200, Thomas Huth wrote: >>>> On Wed, 13 May 2015 16:30:16 +1000 >>>> Alexey Kardashevskiy <aik@ozlabs.ru> wrote: >>>> >>>>> On 05/13/2015 03:33 PM, Gavin Shan wrote: >>>>>> On Tue, May 12, 2015 at 01:38:54AM +1000, Alexey Kardashevskiy wrote: >>>>>>> At the moment iommu_free_table() only releases memory if >>>>>>> the table was initialized for the platform code use, i.e. it had >>>>>>> it_map initialized (which purpose is to track DMA memory space use). >>>>>>> >>>>>>> With dynamic DMA windows, we will need to be able to release >>>>>>> iommu_table even if it was used for VFIO in which case it_map is NULL >>>>>>> so does the patch. >>>>>>> >>>>>>> Signed-off-by: Alexey Kardashevskiy <aik@ozlabs.ru> >>>>>> >>>>>> Reviewed-by: Gavin Shan <gwshan@linux.vnet.ibm.com> >>>>>> >>>>>>> --- >>>>>>> arch/powerpc/kernel/iommu.c | 3 +-- >>>>>>> 1 file changed, 1 insertion(+), 2 deletions(-) >>>>>>> >>>>>>> diff --git a/arch/powerpc/kernel/iommu.c b/arch/powerpc/kernel/iommu.c >>>>>>> index 3d47eb3..2c02d4c 100644 >>>>>>> --- a/arch/powerpc/kernel/iommu.c >>>>>>> +++ b/arch/powerpc/kernel/iommu.c >>>>>>> @@ -714,8 +714,7 @@ void iommu_free_table(struct iommu_table *tbl, const char *node_name) >>>>>>> unsigned int order; >>>>>>> >>>>>>> if (!tbl || !tbl->it_map) { >>>>>>> - printk(KERN_ERR "%s: expected TCE map for %s\n", __func__, >>>>>>> - node_name); >>>>>>> + kfree(tbl); >>>>>> >>>>>> I'm not sure if the "tbl" needs to be checked against NULL as kfree() already >>>>>> has the check. But it looks a bit strange to free NULL "tbl" from the code >>>>>> itself. >>>>> >>>>> Yeah, looks a bit weird, agree, I'll change but in general kfree/vfree/... >>>>> - they all check the passed pointer for NULL. >>>> >>>> But if tbl is NULL, the tbl->it_map check will fail, won't it? So in >>>> this case, I think you have to keep it. >>>> >>> >>> If I understood your question correctly, "tbl->it_map" won't be checked >>> when "tbl" is NULL because the connection ("||") for the two conditions. >>> The code can be changed to something like below if Alexey want: >>> >>> if (!tbl) >>> return; >>> if (!tbl->itmap) >>> kfree(tbl); >> >> To be precise ;) >> >> if (!tbl->itmap) { >> kfree(tbl); >> return; >> } > > I hope that's not your solution, it clearly segfaults with a null > pointer de-ref if !tbl, which is apparently a concern down this path.
I meant the second "if" needs fixing. I need the first one - "if (!tbl)" - anyway. What did I miss?
-- Alexey
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