zfs: unbreak stable/13 clang build on i386 after b0c251b0d

[mm]

Summary

Add missing atomic operations from atomic.c

[mav]

Aaa... While the patch may be OK, I am surprised that my e76373de7b7384bb6e5c6fd5e04f15b54df20fb7 was merged into zfs-2.1-release before fef8bd41fc178d7212957b611c9bc81fe10cb63e. Merge in proper order would not cause this problem in first place. Do you have a clue why it was not done that way?

[mm]

I assume Brian just forgot to merge that commit or intentionally didn't merge that commit and did not inspect your commit for changes in that direction. The i386 build should be broken for Linux as well.

[mav]

Could you ask him to merge the dependency instead of creating unneeded divergence, unless there is a good cause?

[mm]

I am definitely going to do that. But in the meantime we need a buildable stable/13 for i386. The solution I am proposing does (temporarily) place an additional file into cddl/lib/libspl what is outside of sys/contrib/openzfs.

[mav]

Actually my original version was written in assembler to be added into atomic.S without using the compiler atomics: https://people.freebsd.org/~mav/zzz3S.patch . I think it would be more consistent with original code. But since it is hopefully temporary, I am fine with any approach.

[mm]

I am in for the assembler code patch. I will prepare an updated version.

[mm]

atomic.S patch by mav