Is there any reason the drift file should be mode 600?
hmurray at megapathdsl.net
Thu Dec 14 01:46:36 UTC 2017
esr at thyrsus.com said:
> Yes. A Unix write(2) under 512 bytes is atomic, and (when to a local
> filesystem) can't be signal-interrupted either. There's a constant PIPE_BUF
> which is historically 512 but may be larger on modern Unixes - I haven't
> looked in a long time. Technically it pertains to pipe reads, but writes
> that length or below are also atomic on disk filesystems.
Where is that documented? I'd expect some alignment constraints.
I'm interested in the case where the chunk written crosses a disk page and
the system crashes after writing the first page but before writing the next
There may be similar problems on the memory buffer. The second page gets
PIPE_BUF is 4096 on this system.
We are only writing a few bytes.
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