K 10
svn:author
V 3
avg
K 8
svn:date
V 27
2019-10-08T11:27:48.565522Z
K 7
svn:log
V 739
zfs: use atomic_load_64 to read atomic variable in dmu_object_alloc_impl

As long as we support ZFS on 32-bit platforms we should do this for all
64-bit variables that are modified in a lockless fashion using atomic
operations.  Otherwise, there is a risk of a reading a torn value.

Here is a rationale for why I am doing this in dmu_object_alloc_impl:
- it's very recent code
- the code deals with object IDs and a number of objects in a file
  system can overflow 32 bits
- incorrect allocation of an object ID may result in hard to debug
  problems
- fixing all plain reads of 64-bit atomic variables is not a trivial
  undertaking to do in one shot, so I chose to do it incrementally

MFC after:	3 weeks
X-MFC after:	r353301, r353176

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