Messages in this thread | | | Date | Thu, 14 May 2015 09:27:45 +1000 | From | Gavin Shan <> | Subject | Re: [PATCH kernel v10 05/34] powerpc/iommu: Always release iommu_table in iommu_free_table() |
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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);
Thanks, Gavin
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