From: David Howells <dhowells@redhat.com>
To: Al Viro <viro@zeniv.linux.org.uk>
Cc: dhowells@redhat.com, linux-fsdevel@vger.kernel.org,
Dave Wysochanski <dwysocha@redhat.com>,
Marc Dionne <marc.dionne@auristor.com>,
"Matthew Wilcox (Oracle)" <willy@infradead.org>,
Christoph Hellwig <hch@lst.de>,
linux-mm@kvack.org, linux-cachefs@redhat.com,
linux-afs@lists.infradead.org, linux-nfs@vger.kernel.org,
linux-cifs@vger.kernel.org, ceph-devel@vger.kernel.org,
v9fs-developer@lists.sourceforge.net,
Trond Myklebust <trond.myklebust@hammerspace.com>,
Anna Schumaker <anna.schumaker@netapp.com>,
Steve French <sfrench@samba.org>,
Dominique Martinet <asmadeus@codewreck.org>,
Jeff Layton <jlayton@redhat.com>,
linux-kernel@vger.kernel.org
Subject: Re: [PATCH v7 01/31] iov_iter: Add ITER_XARRAY
Date: Sun, 25 Apr 2021 14:58:02 +0100 [thread overview]
Message-ID: <3388475.1619359082@warthog.procyon.org.uk> (raw)
In-Reply-To: <YIVrJT8GwLI0Wlgx@zeniv-ca.linux.org.uk>
Al Viro <viro@zeniv.linux.org.uk> wrote:
> > +struct address_space;
> > struct pipe_inode_info;
> >
> > struct kvec {
>
> What is that chunk for?
Ah, that can go. It used to be ITER_MAPPING.
> > + }),
> > + ({
> > + rem = copy_mc_to_page(v.bv_page, v.bv_offset,
> > + (from += v.bv_len) - v.bv_len, v.bv_len);
> > + if (rem) {
> > + curr_addr = (unsigned long) from;
> > + bytes = curr_addr - s_addr - rem;
> > + rcu_read_unlock();
> > + return bytes;
> > + }
>
> That's broken, same way as kvec and bvec cases are in the same primitive.
> Iterator not advanced on failure halfway through.
Okay. I just copied what ITER_BVEC does. Should this be handled in
iterate_and_advance() rather than in the code snippets it takes as parameters?
But for the moment, I guess I should just add:
i->iov_offset += bytes;
to all three (kvec, bvec and xarray)?
> > @@ -1246,7 +1349,8 @@ unsigned long iov_iter_alignment(const struct iov_iter *i)
> > iterate_all_kinds(i, size, v,
> > (res |= (unsigned long)v.iov_base | v.iov_len, 0),
> > res |= v.bv_offset | v.bv_len,
> > - res |= (unsigned long)v.iov_base | v.iov_len
> > + res |= (unsigned long)v.iov_base | v.iov_len,
> > + res |= v.bv_offset | v.bv_len
> > )
> > return res;
> > }
>
> Hmm... That looks like a really bad overkill - do you need anything beyond
> count and iov_offset in that case + perhaps "do we have the very last page"?
> IOW, do you need to iterate anything at all here? What am I missing here?
Good point. I wonder, even, if the alignment could just be set to 1. There's
no kdoc description on the function that says what the result is meant to
represent.
> > @@ -1268,7 +1372,9 @@ unsigned long iov_iter_gap_alignment(const struct iov_iter *i)
> > ...
> Very limited use; it shouldn't be called for anything other than IOV_ITER case.
Should that just be cut down, then?
> > @@ -1849,7 +2111,12 @@ int iov_iter_for_each_range(struct iov_iter *i, size_t bytes,
> > ...
>
> Would be easier to have that sucker removed first...
I could do that. I'd rather not do that here since it hasn't sat in
linux-next, but since nothing uses it, but Linus might permit it.
David
next prev parent reply other threads:[~2021-04-25 13:58 UTC|newest]
Thread overview: 53+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-04-23 13:27 [PATCH v7 00/31] Network fs helper library & fscache kiocb API David Howells
2021-04-23 13:28 ` [PATCH v7 01/31] iov_iter: Add ITER_XARRAY David Howells
2021-04-23 14:06 ` Matthew Wilcox
2021-04-23 14:33 ` David Howells
2021-04-25 13:14 ` Al Viro
2021-04-25 13:58 ` David Howells [this message]
2021-04-25 14:16 ` Al Viro
2021-04-26 18:54 ` Al Viro
2021-04-26 19:15 ` Jeff Layton
2021-04-26 19:23 ` David Howells
2021-04-26 19:52 ` Al Viro
2021-04-23 13:28 ` [PATCH v7 02/31] mm: Add set/end/wait functions for PG_private_2 David Howells
2021-04-23 13:28 ` [PATCH v7 03/31] mm/filemap: Pass the file_ra_state in the ractl David Howells
2021-04-23 13:28 ` [PATCH v7 04/31] fs: Document file_ra_state David Howells
2021-04-23 13:28 ` [PATCH v7 05/31] mm/readahead: Handle ractl nr_pages being modified David Howells
2021-04-23 13:29 ` [PATCH v7 06/31] mm: Implement readahead_control pageset expansion David Howells
2021-04-23 13:29 ` [PATCH v7 07/31] netfs: Make a netfs helper module David Howells
2021-04-29 8:04 ` Geert Uytterhoeven
2021-04-29 8:41 ` David Howells
2021-04-29 8:43 ` Dominique Martinet
2021-04-23 13:29 ` [PATCH v7 08/31] netfs: Documentation for helper library David Howells
2021-04-23 13:29 ` [PATCH v7 09/31] netfs, mm: Move PG_fscache helper funcs to linux/netfs.h David Howells
2021-04-23 13:29 ` [PATCH v7 10/31] netfs, mm: Add set/end/wait_on_page_fscache() aliases David Howells
2021-04-23 13:30 ` [PATCH v7 11/31] netfs: Provide readahead and readpage netfs helpers David Howells
2021-04-23 13:30 ` [PATCH v7 12/31] netfs: Add tracepoints David Howells
2021-04-23 13:30 ` [PATCH v7 13/31] netfs: Gather stats David Howells
2021-04-23 13:30 ` [PATCH v7 14/31] netfs: Add write_begin helper David Howells
2021-04-23 13:31 ` [PATCH v7 15/31] netfs: Define an interface to talk to a cache David Howells
2021-04-23 13:31 ` [PATCH v7 16/31] netfs: Add a tracepoint to log failures that would be otherwise unseen David Howells
2021-04-23 13:31 ` [PATCH v7 17/31] fscache, cachefiles: Add alternate API to use kiocb for read/write to cache David Howells
2021-04-23 13:32 ` [PATCH v7 18/31] afs: Disable use of the fscache I/O routines David Howells
2021-04-23 13:32 ` [PATCH v7 19/31] afs: Pass page into dirty region helpers to provide THP size David Howells
2021-04-23 13:32 ` [PATCH v7 20/31] afs: Print the operation debug_id when logging an unexpected data version David Howells
2021-04-23 13:32 ` [PATCH v7 21/31] afs: Move key to afs_read struct David Howells
2021-04-23 13:33 ` [PATCH v7 22/31] afs: Don't truncate iter during data fetch David Howells
2021-04-23 13:33 ` [PATCH v7 23/31] afs: Log remote unmarshalling errors David Howells
2021-04-23 13:33 ` [PATCH v7 24/31] afs: Set up the iov_iter before calling afs_extract_data() David Howells
2021-04-23 13:33 ` [PATCH v7 25/31] afs: Use ITER_XARRAY for writing David Howells
2021-04-23 13:33 ` [PATCH v7 26/31] afs: Wait on PG_fscache before modifying/releasing a page David Howells
2021-04-23 13:34 ` [PATCH v7 27/31] afs: Extract writeback extension into its own function David Howells
2021-04-23 13:34 ` [PATCH v7 28/31] afs: Prepare for use of THPs David Howells
2021-04-23 13:34 ` [PATCH v7 29/31] afs: Use the fs operation ops to handle FetchData completion David Howells
2021-04-23 13:34 ` [PATCH v7 30/31] afs: Use new netfs lib read helper API David Howells
2021-04-23 13:34 ` [PATCH v7 31/31] afs: Use the netfs_write_begin() helper David Howells
2021-04-25 23:14 ` [PATCH] iov_iter: Four fixes for ITER_XARRAY David Howells
2021-04-26 17:14 ` Al Viro
2021-04-26 19:02 ` Jeff Layton
2021-04-26 21:38 ` David Wysochanski
2021-04-26 21:06 ` [PATCH] netfs: Miscellaneous fixes David Howells
2021-04-26 21:09 ` Matthew Wilcox
2021-04-26 21:20 ` [PATCH v2] " David Howells
2021-04-26 22:06 ` Matthew Wilcox
2021-04-26 22:17 ` Jeff Layton
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