linux-kernel - Re: [PATCH 7/7] iov_iter: remove iov_iter_is

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Message-ID: <aJDAx1Ns9Fg7F6iK@kbusch-mbp>
Date: Mon, 4 Aug 2025 08:16:39 -0600
From: Keith Busch <kbusch@...nel.org>
To: Mike Snitzer <snitzer@...nel.org>
Cc: Keith Busch <kbusch@...a.com>, linux-block@...r.kernel.org,
	linux-fsdevel@...r.kernel.org, linux-kernel@...r.kernel.org,
	axboe@...nel.dk, dw@...idwei.uk, brauner@...nel.org,
	Chuck Lever <chuck.lever@...cle.com>, linux-nfs@...r.kernel.org
Subject: Re: [PATCH 7/7] iov_iter: remove iov_iter_is_aligned

On Fri, Aug 01, 2025 at 10:02:49PM -0400, Mike Snitzer wrote:
> On Fri, Aug 01, 2025 at 04:47:36PM -0700, Keith Busch wrote:
> > From: Keith Busch <kbusch@...nel.org>
> > 
> > No more callers.
> > 
> > Signed-off-by: Keith Busch <kbusch@...nel.org>
> 
> You had me up until this last patch.
> 
> I'm actually making use of iov_iter_is_aligned() in a series of
> changes for both NFS and NFSD.  Chuck has included some of the
> NFSD changes in his nfsd-testing branch, see:
> https://git.kernel.org/pub/scm/linux/kernel/git/cel/linux.git/commit/?h=nfsd-testing&id=5d78ac1e674b45f9c9e3769b48efb27c44f4e4d3
> 
> And the balance of my work that is pending review/inclusion is:
> https://lore.kernel.org/linux-nfs/20250731230633.89983-1-snitzer@kernel.org/
> https://lore.kernel.org/linux-nfs/20250801171049.94235-1-snitzer@kernel.org/
> 
> I only need iov_iter_aligned_bvec, but recall I want to relax its
> checking with this patch:
> https://lore.kernel.org/linux-nfs/20250708160619.64800-5-snitzer@kernel.org/
> 
> Should I just add iov_iter_aligned_bvec() to fs/nfs_common/ so that
> both NFS and NFSD can use it?

If at all possible, I recommend finding a place that already walks the
vectors and do an opprotunistic check for the alignments there. This
will save CPU cycles. For example, nfsd_iter_read already iterates the
bvec while setting each page. Could you check the alignment while doing
that instead of iterating a second time immediately after?