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Message-ID: <289825.1617959345@warthog.procyon.org.uk>
Date: Fri, 09 Apr 2021 10:09:05 +0100
From: David Howells <dhowells@...hat.com>
To: Al Viro <viro@...iv.linux.org.uk>
Cc: dhowells@...hat.com, linux-fsdevel@...r.kernel.org,
"Matthew Wilcox (Oracle)" <willy@...radead.org>,
Christoph Hellwig <hch@....de>, linux-mm@...ck.org,
linux-cachefs@...hat.com, linux-afs@...ts.infradead.org,
linux-nfs@...r.kernel.org, linux-cifs@...r.kernel.org,
ceph-devel@...r.kernel.org, v9fs-developer@...ts.sourceforge.net,
Trond Myklebust <trond.myklebust@...merspace.com>,
Anna Schumaker <anna.schumaker@...app.com>,
Steve French <sfrench@...ba.org>,
Dominique Martinet <asmadeus@...ewreck.org>,
Jeff Layton <jlayton@...hat.com>,
David Wysochanski <dwysocha@...hat.com>,
linux-kernel@...r.kernel.org
Subject: Re: [PATCH v6 01/30] iov_iter: Add ITER_XARRAY
Al Viro <viro@...iv.linux.org.uk> wrote:
> > +#define iterate_all_kinds(i, n, v, I, B, K, X) { \
>
> Do you have any users that would pass different B and X?
>
> > @@ -1440,7 +1665,7 @@ ssize_t iov_iter_get_pages_alloc(struct iov_iter *i,
> > return v.bv_len;
> > }),({
> > return -EFAULT;
> > - })
> > + }), 0
>
> Correction - users that might get that flavour. This one explicitly checks
> for xarray and doesn't get to iterate_... in that case.
This is the case for iterate_all_kinds(), but not for iterate_and_advance().
See _copy_mc_to_iter() for example: that can return directly out of the middle
of the loop, so the X variant must drop the rcu_read_lock(), but the B variant
doesn't need to. You also can't just use break to get out as the X variant
has a loop within a loop to handle iteration over the subelements of a THP.
But with iterate_all_kinds(), I could just drop the X parameter and use the B
parameter for both, I think.
David
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