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From: David Wysochanski <dwysocha@redhat.com>
To: Matthew Wilcox <willy@infradead.org>
Cc: David Howells <dhowells@redhat.com>,
	Trond Myklebust <trondmy@hammerspace.com>,
	Anna Schumaker <anna.schumaker@netapp.com>,
	Steve French <sfrench@samba.org>,
	Dominique Martinet <asmadeus@codewreck.org>,
	Jeff Layton <jlayton@redhat.com>,
	Alexander Viro <viro@zeniv.linux.org.uk>,
	linux-cachefs@redhat.com, linux-afs@lists.infradead.org,
	linux-nfs <linux-nfs@vger.kernel.org>,
	linux-cifs <linux-cifs@vger.kernel.org>,
	ceph-devel@vger.kernel.org, v9fs-developer@lists.sourceforge.net,
	linux-fsdevel <linux-fsdevel@vger.kernel.org>,
	Linux Kernel Mailing List <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH 32/32] NFS: Convert readpage to readahead and use netfs_readahead for fscache
Date: Tue, 26 Jan 2021 13:25:59 -0500
Message-ID: <CALF+zO=4kyvR+9T48ZF6Cu-izLkbs-1m3S_ebDNWv-zuC5GSRA@mail.gmail.com> (raw)
In-Reply-To: <20210126013611.GI308988@casper.infradead.org>

On Mon, Jan 25, 2021 at 8:37 PM Matthew Wilcox <willy@infradead.org> wrote:
>
>
> For Subject: s/readpage/readpages/
>
Fixed

> On Mon, Jan 25, 2021 at 09:37:29PM +0000, David Howells wrote:
> > +int __nfs_readahead_from_fscache(struct nfs_readdesc *desc,
> > +                              struct readahead_control *rac)
>
> I thought you wanted it called ractl instead of rac?  That's what I've
> been using in new code.
>
Fixed

> > -     dfprintk(FSCACHE, "NFS: nfs_getpages_from_fscache (0x%p/%u/0x%p)\n",
> > -              nfs_i_fscache(inode), npages, inode);
> > +     dfprintk(FSCACHE, "NFS: nfs_readahead_from_fscache (0x%p/0x%p)\n",
> > +              nfs_i_fscache(inode), inode);
>
> We do have readahead_count() if this is useful information to be logging.
>
Right, I used it elsewhere so I'll add here as well.

> > +static inline int nfs_readahead_from_fscache(struct nfs_readdesc *desc,
> > +                                          struct readahead_control *rac)
> >  {
> > -     if (NFS_I(inode)->fscache)
> > -             return __nfs_readpages_from_fscache(ctx, inode, mapping, pages,
> > -                                                 nr_pages);
> > +     if (NFS_I(rac->mapping->host)->fscache)
> > +             return __nfs_readahead_from_fscache(desc, rac);
> >       return -ENOBUFS;
> >  }
>
> Not entirely sure that it's worth having the two functions separated any more.
>
Yeah it's questionable so I'll collapse.  I'll also do that with
nfs_readpage_from_fscache().

> >       /* attempt to read as many of the pages as possible from the cache
> >        * - this returns -ENOBUFS immediately if the cookie is negative
> >        */
> > -     ret = nfs_readpages_from_fscache(desc.ctx, inode, mapping,
> > -                                      pages, &nr_pages);
> > +     ret = nfs_readahead_from_fscache(&desc, rac);
> >       if (ret == 0)
> >               goto read_complete; /* all pages were read */
> >
> >       nfs_pageio_init_read(&desc.pgio, inode, false,
> >                            &nfs_async_read_completion_ops);
> >
> > -     ret = read_cache_pages(mapping, pages, readpage_async_filler, &desc);
> > +     while ((page = readahead_page(rac))) {
> > +             ret = readpage_async_filler(&desc, page);
> > +             put_page(page);
> > +     }
>
> I thought with the new API we didn't need to do this kind of thing
> any more?  ie no matter whether fscache is configured in or not, it'll
> submit the I/Os.
>

We don't. This patchset was only intended as a stepping stone to get the
netfs API accepted with minimal invasiveness in NFS.

I have another patch which will unconditionally call netfs API but I
didn't post it. Since I'm not an NFS maintainer, and maintainer's didn't
weigh in on the approach, I opted to go with the least invasive approach.

There's an NFS "remote bakeathon" coming up at the end of Feb.
That would probably be a good time to get further testing on NFS
unconditionally calling the netfs API, and we should be able to
cover things like any performance concerns, etc.


      parent reply index

Thread overview: 41+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-01-25 21:30 [PATCH 00/32] Network fs helper library & fscache kiocb API [ver #2] David Howells
2021-01-25 21:31 ` [PATCH 01/32] iov_iter: Add ITER_XARRAY David Howells
2021-01-25 21:31 ` [PATCH 02/32] vm: Add wait/unlock functions for PG_fscache David Howells
2021-01-25 21:31 ` [PATCH 03/32] mm: Implement readahead_control pageset expansion David Howells
2021-01-25 21:31 ` [PATCH 04/32] vfs: Export rw_verify_area() for use by cachefiles David Howells
2021-01-25 21:31 ` [PATCH 05/32] netfs: Make a netfs helper module David Howells
2021-01-25 21:32 ` [PATCH 06/32] netfs: Provide readahead and readpage netfs helpers David Howells
2021-01-25 21:32 ` [PATCH 07/32] netfs: Add tracepoints David Howells
2021-01-25 21:32 ` [PATCH 08/32] netfs: Gather stats David Howells
2021-01-25 21:32 ` [PATCH 09/32] netfs: Add write_begin helper David Howells
2021-01-25 21:32 ` [PATCH 10/32] netfs: Define an interface to talk to a cache David Howells
2021-01-25 21:32 ` [PATCH 11/32] fscache, cachefiles: Add alternate API to use kiocb for read/write to cache David Howells
2021-01-25 21:33 ` [PATCH 12/32] afs: Disable use of the fscache I/O routines David Howells
2021-01-25 21:33 ` [PATCH 13/32] afs: Pass page into dirty region helpers to provide THP size David Howells
2021-01-25 21:33 ` [PATCH 14/32] afs: Print the operation debug_id when logging an unexpected data version David Howells
2021-01-25 21:33 ` [PATCH 15/32] afs: Move key to afs_read struct David Howells
2021-01-25 21:34 ` [PATCH 16/32] afs: Don't truncate iter during data fetch David Howells
2021-01-25 21:34 ` [PATCH 17/32] afs: Log remote unmarshalling errors David Howells
2021-01-25 21:34 ` [PATCH 18/32] afs: Set up the iov_iter before calling afs_extract_data() David Howells
2021-01-25 21:34 ` [PATCH 19/32] afs: Use ITER_XARRAY for writing David Howells
2021-01-25 21:34 ` [PATCH 20/32] afs: Wait on PG_fscache before modifying/releasing a page David Howells
2021-01-25 21:35 ` [PATCH 21/32] afs: Extract writeback extension into its own function David Howells
2021-01-25 21:35 ` [PATCH 22/32] afs: Prepare for use of THPs David Howells
2021-01-25 21:35 ` [PATCH 23/32] afs: Use the fs operation ops to handle FetchData completion David Howells
2021-01-25 21:35 ` [PATCH 24/32] afs: Use new fscache read helper API David Howells
2021-01-25 21:35 ` [PATCH 25/32] NFS: Clean up nfs_readpage() and nfs_readpages() David Howells
2021-01-26  3:59   ` Matthew Wilcox
2021-01-26 15:33     ` David Wysochanski
2021-01-25 21:36 ` [PATCH 26/32] NFS: In nfs_readpage() only increment NFSIOS_READPAGES when read succeeds David Howells
2021-01-25 21:36 ` [PATCH 27/32] NFS: Refactor nfs_readpage() and nfs_readpage_async() to use nfs_readdesc David Howells
2021-01-26  4:05   ` Matthew Wilcox
2021-01-26 15:24     ` David Wysochanski
2021-01-25 21:36 ` [PATCH 28/32] NFS: Call readpage_async_filler() from nfs_readpage_async() David Howells
2021-01-25 21:36 ` [PATCH 29/32] NFS: Add nfs_pageio_complete_read() and remove nfs_readpage_async() David Howells
2021-01-25 21:37 ` [PATCH 30/32] NFS: Allow internal use of read structs and functions David Howells
2021-01-25 21:37 ` [PATCH 31/32] NFS: Convert to the netfs API and nfs_readpage to use netfs_readpage David Howells
2021-01-25 21:37 ` [PATCH 32/32] NFS: Convert readpage to readahead and use netfs_readahead for fscache David Howells
2021-01-26  1:36   ` Matthew Wilcox
2021-01-26 15:24     ` Chuck Lever
2021-01-26 19:10       ` David Wysochanski
2021-01-26 18:25     ` David Wysochanski [this message]

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