linux-kernel - Re: [PATCH v5] fs/9p: remove writeback fid and fix per-file modes

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Date:   Tue, 25 Apr 2023 20:13:27 +0900
From:   asmadeus@...ewreck.org
To:     Christophe JAILLET <christophe.jaillet@...adoo.fr>
Cc:     Eric Van Hensbergen <ericvh@...nel.org>,
        v9fs-developer@...ts.sourceforge.net,
        linux-fsdevel@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux_oss@...debyte.com
Subject: Re: [PATCH v5] fs/9p: remove writeback fid and fix per-file modes

Christophe JAILLET wrote on Tue, Apr 25, 2023 at 09:11:01AM +0200:
> This code looks strange.
> P9_OWRITE is 0x01, so !P9_OWRITE is 0.
> So the code is equivalent to "p9_omode = P9_ORDWR;"
> 
> Is it what is expexted?
> 
> Maybe
> 	p9_omode = (p9_omode & ~P9_OWRITE) | P9_ORDWR;
> ?

Since we're discussing tooling, sparse caught this one:
fs/9p/vfs_inode.c:826:38: warning: dubious: x & !y
fs/9p/vfs_inode_dotl.c:291:38: warning: dubious: x & !y

(runing with make `M=fs/9p W=1 C=2` ; unfortunately error code doesn't
reflect a problem so that'll require inspecting output to automate...)


I've tried running scan-build in a very old-fashioned way (getting the
gcc lines from make V=1 and re-running with scan-build) and it had some
arguable warnings (setting `ret = 0` before it is overwritten again is
considered a dead store), but it had some real problems as well so it
might be worth fixing these just to reduce the clutter and run it all
the time.
I'll post a couple of patches tomorrow (unrelated to this)

-- 
Dominique