[patch 083/146] include/linux/gfp.h: further document GFP_DMA32

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From: Miles Chen <miles.chen@xxxxxxxxxxxx>
Subject: include/linux/gfp.h: further document GFP_DMA32

kmalloc(..., GFP_DMA32) does not return DMA32 memory because the DMA32
kmalloc cache array is not implemented.  (Reason: there is no such user in
kernel).

Put a short comment about this so people can understand this by reading
the comment.

[1] https://lists.linuxfoundation.org/pipermail/iommu/2018-December/031696.html

Link: https://lkml.kernel.org/r/20211207093610.6406-1-miles.chen@xxxxxxxxxxxx
Signed-off-by: Miles Chen <miles.chen@xxxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---

 include/linux/gfp.h |    4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

--- a/include/linux/gfp.h~gfp-further-document-gfp_dma32
+++ a/include/linux/gfp.h
@@ -302,7 +302,9 @@ struct vm_area_struct;
  * lowest zone as a type of emergency reserve.
  *
  * %GFP_DMA32 is similar to %GFP_DMA except that the caller requires a 32-bit
- * address.
+ * address. Note that kmalloc(..., GFP_DMA32) does not return DMA32 memory
+ * because the DMA32 kmalloc cache array is not implemented.
+ * (Reason: there is no such user in kernel).
  *
  * %GFP_HIGHUSER is for userspace allocations that may be mapped to userspace,
  * do not need to be directly accessible by the kernel but that cannot
_



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