[PATCH v4] mm: cma: indefinitely retry allocations in cma_alloc

[Chris Goldsworthy]

V1: Introduces a retry loop that attempts a CMA allocation a finite
number of times before giving up:
 
https://lkml.org/lkml/2020/8/5/1097
https://lkml.org/lkml/2020/8/11/893

V2: Introduces an indefinite retry for CMA allocations.  David Hildenbrand
raised a page pinning example which precludes doing this infite-retrying
for all CMA users:

https://lkml.org/lkml/2020/9/17/984

V3: Re-introduce a GFP mask argument for cma_alloc(), that can take in
__GFP_NOFAIL as an argument to indicate that a CMA allocation should be
retried indefinitely. This lets callers of cma_alloc() decide if they want
to perform indefinite retires. Also introduces a config option for
controlling the duration of the sleep between retries:

https://www.spinics.net/lists/linux-mm/msg228778.html

V4: In response to comments by Minchan Kim, we make the sleep interruptable
and remove a defconfig option controlling how long the sleep lasts for (it
is now a fixed 100 ms).

Chris Goldsworthy (1):
  mm: cma: indefinitely retry allocations in cma_alloc

 arch/powerpc/kvm/book3s_hv_builtin.c       |  2 +-
 drivers/dma-buf/heaps/cma_heap.c           |  2 +-
 drivers/s390/char/vmcp.c                   |  2 +-
 drivers/staging/android/ion/ion_cma_heap.c |  2 +-
 include/linux/cma.h                        |  2 +-
 kernel/dma/contiguous.c                    |  4 ++--
 mm/cma.c                                   | 36 +++++++++++++++++++++++++-----
 mm/cma_debug.c                             |  2 +-
 mm/hugetlb.c                               |  4 ++--
 9 files changed, 40 insertions(+), 16 deletions(-)

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