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Date: Sun, 18 Dec 2016 03:26:12 +0000
From: Al Viro <viro@ZenIV.linux.org.uk>
To: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
        linux-fsdevel <linux-fsdevel@vger.kernel.org>,
        "Darrick J. Wong" <darrick.wong@oracle.com>
Subject: Re: [git pull] vfs.git pile 2
Message-ID: <20161218032605.GW1555@ZenIV.linux.org.uk>
References: <20161216221218.GT1555@ZenIV.linux.org.uk>
 <CA+55aFwdh+VBdNY_gHc+CKMDznBwft+THQE9jBwfSojqOf72BQ@mail.gmail.com>
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[Darrick Cc'd]
On Sat, Dec 17, 2016 at 06:49:55PM -0800, Linus Torvalds wrote:
> On Fri, Dec 16, 2016 at 2:12 PM, Al Viro <viro@zeniv.linux.org.uk> wrote:
> > In this pile:
> >         * autofs-namespace series
> >         * dedupe stuff
> >         * more struct path constification
> 
> When looking at the conflict, I looked at that part of
> vfs_clone_file_prep_inodes(), and reacted to the insanity.
> 
> WTF?
> 
>         /* Zero length dedupe exits immediately; reflink goes to EOF. */
>         if (*len == 0) {
>                 if (is_dedupe) {
>                         *len = 0;
>                         return 0;
>                 }
>                 *len = isize - pos_in;
>         }
> 
> I'll just leave you to read through that part a bit more. Because
> there are two completely insane things going on in that code sequence.

One, AFAICS - pointless *len = 0 in case of is_dedupe.  That's a counterpart of
	/* Zero length dedupe exits immediately; reflink goes to EOF. */
	if (len == 0) {
		if (is_dedupe) {
			ret = 0;
			goto out_unlock;
		}
		len = isize - pos_in;
	}
in mainline xfs_reflink_remap_range().  What else am I missing there?
I'm not thrilled with the calling conventions they'd used, and that
*len = 0; shouldn't have been slapped there (at a guess, by inertia from
the conversion of the chunk right before that one -
	/* Are we going all the way to the end? */
	isize = i_size_read(inode_in);
	if (isize == 0) {
		ret = 0;
		goto out_unlock;
	}
in mainline, needing *len = 0; after conversion), but I don't see what else
are you refering to in that snippet...