code review 94070044: os: cut limited read to 1 GB

os: cut limited read to 1 GB

If systems actually read that much, using 2GB-1 will
result in misaligned subsequent reads. Use 1GB instead,
which will certainly keep reads aligned and which is
plenty large enough.

Update issue 7812.

[rsc, 2014-05-02 15:43:24]

Hello bradfitz (cc: golang-codereviews@googlegroups.com),

I'd like you to review this change to
https://code.google.com/p/go/

[bradfitz, 2014-05-02 15:52:39]

LGTM

I'd expand the comment a bit more with this rationale but I suppose it'll
be in the linked issue anyway.
 On May 2, 2014 11:43 AM, <rsc@golang.org> wrote:

> Reviewers: bradfitz,
>
> Message:
> Hello bradfitz (cc: golang-codereviews@googlegroups.com),
>
> I'd like you to review this change to
> https://code.google.com/p/go/
>
>
> Description:
> os: cut limited read to 1 GB
>
> If systems actually read that much, using 2GB-1 will
> result in misaligned subsequent reads. Use 1GB instead,
> which will certainly keep reads aligned and which is
> plenty large enough.
>
> Update issue 7812.
>
> Please review this at https://codereview.appspot.com/94070044/
>
> Affected files (+1, -1 lines):
>   M src/pkg/os/file_unix.go
>
>
> Index: src/pkg/os/file_unix.go
> ===================================================================
> --- a/src/pkg/os/file_unix.go
> +++ b/src/pkg/os/file_unix.go
> @@ -176,7 +176,7 @@
>  // even on 64-bit systems. See golang.org/issue/7812.
>  const (
>         needsMaxRW = runtime.GOOS == "darwin" || runtime.GOOS == "freebsd"
> -       maxRW      = 2<<30 - 1
> +       maxRW      = 1 << 30
>  )
>
>  // read reads up to len(b) bytes from the File.
>
>
>

[rsc, 2014-05-02 16:12:21]

expanded comment

[rsc, 2014-05-02 16:12:45]

*** Submitted as https://code.google.com/p/go/source/detail?r=15e9d3c5d705 ***

os: cut limited read to 1 GB

If systems actually read that much, using 2GB-1 will
result in misaligned subsequent reads. Use 1GB instead,
which will certainly keep reads aligned and which is
plenty large enough.

Update issue 7812.

LGTM=bradfitz
R=bradfitz
CC=golang-codereviews
https://codereview.appspot.com/94070044