Date: Wed, 10 Apr 2013 22:01:10 +0300 From: Konstantin Belousov <kostikbel@gmail.com> To: Matthew Rezny <mrezny@hexaneinc.com> Cc: freebsd-standards@FreeBSD.org Subject: Re: standards/177742: conflict of dd's bs= option with use of conv=sparse Message-ID: <20130410190110.GM2930@kib.kiev.ua> In-Reply-To: <201304101410.r3AEA1vH044880@freefall.freebsd.org>
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On Wed, Apr 10, 2013 at 02:10:01PM +0000, Matthew Rezny wrote:
> The following reply was made to PR standards/177742; it has been noted by GNATS.
>
> From: Matthew Rezny <mrezny@hexaneinc.com>
> To: bug-followup@FreeBSD.org
> Cc:
> Subject: Re: standards/177742: conflict of dd's bs= option with use of
> conv=sparse
> Date: Wed, 10 Apr 2013 15:31:08 +0200
>
> The patch I suggested got a little messed up by the web form, and it
> also contained a typo. Further, I had neglected to consider the
> C_BS flag itself should be present after masking off the few allowed
> flags, so the patch should be amended as such follows.
>
> if (ddflags & C_BS) {
> out.dbcnt = in.dbcnt;
> - dd_out(1);
> + dd_out((ddflags & !(C_NOERROR | C_NOTRUNC | C_SYNC)) == C_BS);
> in.dbcnt = 0;
> continue;
> }
>
> This patch has been tested to confirm conv=sparse now works as expected
> with bs= set. No other conversions have been checked with the bs=
> option and from reading the code I don't think they will.
I somehow followed what you wrote.
Still, I think your patch is not correct. Its result is always using the
block coalescing mode there. The issue is that the '!' operator result
is defined to be either 0 or 1, which mask and-ed with ddflags never could
be equal to the C_BS == 4. You probably mean '~' ?
In fact, the test in the containing if () means that C_BS is guaranteed
to be set there.
So my question is, do you want to explicitely check that no other flags
are set, except noerror, notrunc, sync and bs ? Or is it yet another bug ?
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