[v1,00/16] .map_sg() error cleanup

Hi,

This series is spun out and expanded from my work to add P2PDMA support
to DMA map operations[1].

The P2PDMA work requires distinguishing different error conditions in
a map_sg operation. dma_map_sgtable() already allows for returning an
error code (where as dma_map_sg() is only allowed to return zero)
however, it currently only returns -EINVAL when a .map_sg() call returns
zero.

This series cleans up all .map_sg() implementations to return appropriate
error codes. After the cleanup, dma_map_sg() will still return zero,
however dma_map_sgtable() will pass the error code from the .map_sg()
call. Thanks go to Martn Oliveira for doing a lot of the cleanup of the
obscure implementations.

The patch set is based off of v5.14-rc1 and a git repo can be found
here:

  https://github.com/sbates130272/linux-p2pmem map_sg_err_cleanup_v1

Thanks,

Logan

[1] https://lore.kernel.org/linux-block/20210513223203.5542-1-logang@deltatee.com/

--

Logan Gunthorpe (5):
  dma-mapping: Allow map_sg() ops to return negative error codes
  dma-direct: Return appropriate error code from dma_direct_map_sg()
  iommu: Return full error code from iommu_map_sg[_atomic]()
  dma-iommu: Return error code from iommu_dma_map_sg()
  dma-mapping: Disallow .map_sg operations from returning zero on error

Martin Oliveira (11):
  alpha: return error code from alpha_pci_map_sg()
  ARM/dma-mapping: return error code from .map_sg() ops
  ia64/sba_iommu: return error code from sba_map_sg_attrs()
  MIPS/jazzdma: return error code from jazz_dma_map_sg()
  powerpc/iommu: return error code from .map_sg() ops
  s390/pci: return error code from s390_dma_map_sg()
  sparc/iommu: return error codes from .map_sg() ops
  parisc: return error code from .map_sg() ops
  xen: swiotlb: return error code from xen_swiotlb_map_sg()
  x86/amd_gart: return error code from gart_map_sg()
  dma-mapping: return error code from dma_dummy_map_sg()

 arch/alpha/kernel/pci_iommu.c           | 10 +++-
 arch/arm/mm/dma-mapping.c               | 22 +++++---
 arch/ia64/hp/common/sba_iommu.c         |  9 +--
 arch/mips/jazz/jazzdma.c                |  2 +-
 arch/powerpc/kernel/iommu.c             |  4 +-
 arch/powerpc/platforms/ps3/system-bus.c |  2 +-
 arch/powerpc/platforms/pseries/vio.c    |  5 +-
 arch/s390/pci/pci_dma.c                 | 12 ++--
 arch/sparc/kernel/iommu.c               |  4 +-
 arch/sparc/kernel/pci_sun4v.c           |  4 +-
 arch/sparc/mm/iommu.c                   |  2 +-
 arch/x86/kernel/amd_gart_64.c           | 16 +++---
 drivers/iommu/dma-iommu.c               | 20 ++++---
 drivers/iommu/iommu.c                   | 15 +++--
 drivers/parisc/ccio-dma.c               |  2 +-
 drivers/parisc/sba_iommu.c              |  2 +-
 drivers/xen/swiotlb-xen.c               |  2 +-
 include/linux/dma-map-ops.h             |  6 +-
 include/linux/dma-mapping.h             | 35 +++---------
 include/linux/iommu.h                   | 22 ++++----
 kernel/dma/direct.c                     |  2 +-
 kernel/dma/dummy.c                      |  2 +-
 kernel/dma/mapping.c                    | 73 ++++++++++++++++++++++---
 23 files changed, 165 insertions(+), 108 deletions(-)


base-commit: e73f0f0ee7541171d89f2e2491130c7771ba58d3
--
2.20.1

On Thu, Jul 15, 2021 at 10:45:28AM -0600, Logan Gunthorpe wrote:
> Hi,
> 
> This series is spun out and expanded from my work to add P2PDMA support
> to DMA map operations[1].
> 
> The P2PDMA work requires distinguishing different error conditions in
> a map_sg operation. dma_map_sgtable() already allows for returning an
> error code (where as dma_map_sg() is only allowed to return zero)
> however, it currently only returns -EINVAL when a .map_sg() call returns
> zero.
> 
> This series cleans up all .map_sg() implementations to return appropriate
> error codes. After the cleanup, dma_map_sg() will still return zero,
> however dma_map_sgtable() will pass the error code from the .map_sg()
> call. Thanks go to Martn Oliveira for doing a lot of the cleanup of the
> obscure implementations.
> 
> The patch set is based off of v5.14-rc1 and a git repo can be found
> here:

Have all the callers for dma_map_sg() been updated to check for error
codes? If not, isn't that a pre-requisit to this patch set?

From what I see in Linus' current tree, we still have cases today
where the return value of dma_map_sg() is compared with zero to
detect failure, so I think that needs fixing before we start changing
the dma_map_sg() implementation to return negative numbers.

I also notice that there are various places that don't check the
return value - and returning a negative number instead of zero may
well cause random other bits to be set in fields.

So, I think there's a fair amount of work to do in all the drivers
before this change can be considered.

On 2021-07-15 10:53 a.m., Russell King (Oracle) wrote:
> On Thu, Jul 15, 2021 at 10:45:28AM -0600, Logan Gunthorpe wrote:
>> Hi,
>>
>> This series is spun out and expanded from my work to add P2PDMA support
>> to DMA map operations[1].
>>
>> The P2PDMA work requires distinguishing different error conditions in
>> a map_sg operation. dma_map_sgtable() already allows for returning an
>> error code (where as dma_map_sg() is only allowed to return zero)
>> however, it currently only returns -EINVAL when a .map_sg() call returns
>> zero.
>>
>> This series cleans up all .map_sg() implementations to return appropriate
>> error codes. After the cleanup, dma_map_sg() will still return zero,
>> however dma_map_sgtable() will pass the error code from the .map_sg()
>> call. Thanks go to Martn Oliveira for doing a lot of the cleanup of the
>> obscure implementations.
>>
>> The patch set is based off of v5.14-rc1 and a git repo can be found
>> here:
> 
> Have all the callers for dma_map_sg() been updated to check for error
> codes? If not, isn't that a pre-requisit to this patch set?

No. Perhaps I wasn't clear enough: This series is changing only
impelemntations of .map_sg(). It does *not* change the return code of
dma_map_sg(). dma_map_sg() will continue to return zero on error for the
foreseeable future. The dma_map_sgtable() call already allows returning
error codes and it will pass the new error code through. This is what
will be used in the P2PDMA work.

Logan