[PATCH] D39464: Define fs::allocate_file which preallocates disk blocks.

[Kamil Rytarowski via llvm-commits]

On 13.11.2017 18:19, Rafael Avila de Espindola wrote:
> Kamil Rytarowski via Phabricator <reviews at reviews.llvm.org> writes:
> 
>> krytarowski added inline comments.
>>
>>
>> ================
>> Comment at: llvm/lib/Support/Unix/Path.inc:436
>>        return std::error_code(Err, std::generic_category());
>> +    return make_error_code(errc::function_not_supported);
>>    }
>> ----------------
>> NetBSD needs `ftruncate`(2) as a fallback for `posix_fallocate`(2).
>>
>> In the default setup `posix_fallocate`() returns EOPNOTSUPP.
> 
> Will ftruncate allocate space on netbsd? Note that it is OK for
> allocate_file to fail. The user then has to use a buffer and write(2)
> instead of mmap for output.
> 
> Cheers,
> Rafael
> 

ftruncate(2)/NetBSD as an extension extends area and makes it
zero-filled. It's equivalent to lseek(2) + write(2).

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