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From: Andreas Gruenbacher <agruenba@redhat.com>
To: Matthew Wilcox <willy@infradead.org>
Cc: "Andreas Grünbacher" <andreas.gruenbacher@gmail.com>,
	"Andrew Morton" <akpm@linux-foundation.org>,
	linux-xfs <linux-xfs@vger.kernel.org>,
	"Junxiao Bi" <junxiao.bi@oracle.com>,
	"William Kucharski" <william.kucharski@oracle.com>,
	"Joseph Qi" <joseph.qi@linux.alibaba.com>,
	"John Hubbard" <jhubbard@nvidia.com>,
	LKML <linux-kernel@vger.kernel.org>,
	linux-f2fs-devel@lists.sourceforge.net,
	cluster-devel <cluster-devel@redhat.com>,
	Linux-MM <linux-mm@kvack.org>,
	ocfs2-devel@oss.oracle.com,
	linux-fsdevel <linux-fsdevel@vger.kernel.org>,
	linux-ext4 <linux-ext4@vger.kernel.org>,
	linux-erofs@lists.ozlabs.org, "Christoph Hellwig" <hch@lst.de>,
	linux-btrfs@vger.kernel.org,
	"Steven Whitehouse" <swhiteho@redhat.com>,
	"Bob Peterson" <rpeterso@redhat.com>
Subject: Re: [Cluster-devel] [PATCH v11 16/25] fs: Convert mpage_readpages to mpage_readahead
Date: Thu, 18 Jun 2020 18:40:15 +0200
Message-ID: <CAHc6FU6TYTiQ0a0GkN1dhh3VeQKVKrL+eALvuYzZ8nq5jvNHjg@mail.gmail.com> (raw)
In-Reply-To: <20200618150309.GP8681@bombadil.infradead.org>

On Thu, Jun 18, 2020 at 5:03 PM Matthew Wilcox <willy@infradead.org> wrote:
>
> On Thu, Jun 18, 2020 at 02:46:03PM +0200, Andreas Gruenbacher wrote:
> > On Wed, Jun 17, 2020 at 4:22 AM Matthew Wilcox <willy@infradead.org> wrote:
> > > On Wed, Jun 17, 2020 at 02:57:14AM +0200, Andreas Grünbacher wrote:
> > > > Right, the approach from the following thread might fix this:
> > > >
> > > > https://lore.kernel.org/linux-fsdevel/20191122235324.17245-1-agruenba@redhat.com/T/#t
> > >
> > > In general, I think this is a sound approach.
> > >
> > > Specifically, I think FAULT_FLAG_CACHED can go away.  map_pages()
> > > will bring in the pages which are in the page cache, so when we get to
> > > gfs2_fault(), we know there's a reason to acquire the glock.
> >
> > We'd still be grabbing a glock while holding a dependent page lock.
> > Another process could be holding the glock and could try to grab the
> > same page lock (i.e., a concurrent writer), leading to the same kind
> > of deadlock.
>
> What I'm saying is that gfs2_fault should just be:
>
> +static vm_fault_t gfs2_fault(struct vm_fault *vmf)
> +{
> +       struct inode *inode = file_inode(vmf->vma->vm_file);
> +       struct gfs2_inode *ip = GFS2_I(inode);
> +       struct gfs2_holder gh;
> +       vm_fault_t ret;
> +       int err;
> +
> +       gfs2_holder_init(ip->i_gl, LM_ST_SHARED, 0, &gh);
> +       err = gfs2_glock_nq(&gh);
> +       if (err) {
> +               ret = block_page_mkwrite_return(err);
> +               goto out_uninit;
> +       }
> +       ret = filemap_fault(vmf);
> +       gfs2_glock_dq(&gh);
> +out_uninit:
> +       gfs2_holder_uninit(&gh);
> +       return ret;
> +}
>
> because by the time gfs2_fault() is called, map_pages() has already been
> called and has failed to insert the necessary page, so we should just
> acquire the glock now instead of trying again to look for the page in
> the page cache.

Okay, that's great.

Thanks,
Andreas


  reply index

Thread overview: 47+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-04-14 15:02 [PATCH v11 00/25] Change readahead API Matthew Wilcox
2020-04-14 15:02 ` [PATCH v11 01/25] mm: Move readahead prototypes from mm.h Matthew Wilcox
2020-04-15  9:10   ` Johannes Thumshirn
2020-04-14 15:02 ` [PATCH v11 02/25] mm: Return void from various readahead functions Matthew Wilcox
2020-04-14 15:02 ` [PATCH v11 03/25] mm: Ignore return value of ->readpages Matthew Wilcox
2020-04-15  9:17   ` Johannes Thumshirn
2020-04-14 15:02 ` [PATCH v11 04/25] mm: Move readahead nr_pages check into read_pages Matthew Wilcox
2020-04-15  9:19   ` Johannes Thumshirn
2020-04-14 15:02 ` [PATCH v11 05/25] mm: Add new readahead_control API Matthew Wilcox
2020-04-15  1:17   ` Andrew Morton
2020-04-15  2:18     ` Matthew Wilcox
2020-04-15  4:56       ` Andrew Morton
2020-04-15 11:22         ` Matthew Wilcox
2020-04-14 15:02 ` [PATCH v11 06/25] mm: Use readahead_control to pass arguments Matthew Wilcox
2020-04-15  9:30   ` Johannes Thumshirn
2020-04-14 15:02 ` [PATCH v11 07/25] mm: Rename various 'offset' parameters to 'index' Matthew Wilcox
2020-04-14 15:02 ` [PATCH v11 08/25] mm: rename readahead loop variable to 'i' Matthew Wilcox
2020-04-15  9:31   ` Johannes Thumshirn
2020-04-14 15:02 ` [PATCH v11 09/25] mm: Remove 'page_offset' from readahead loop Matthew Wilcox
2020-04-14 15:02 ` [PATCH v11 10/25] mm: Put readahead pages in cache earlier Matthew Wilcox
2020-04-14 15:02 ` [PATCH v11 11/25] mm: Add readahead address space operation Matthew Wilcox
2020-04-14 15:02 ` [PATCH v11 12/25] mm: Move end_index check out of readahead loop Matthew Wilcox
2020-04-14 15:02 ` [PATCH v11 13/25] mm: Add page_cache_readahead_unbounded Matthew Wilcox
2020-04-14 15:02 ` [PATCH v11 14/25] mm: Document why we don't set PageReadahead Matthew Wilcox
2020-04-14 15:02 ` [PATCH v11 15/25] mm: Use memalloc_nofs_save in readahead path Matthew Wilcox
2020-04-14 15:02 ` [PATCH v11 16/25] fs: Convert mpage_readpages to mpage_readahead Matthew Wilcox
2020-06-16 22:36   ` [Cluster-devel] " Andreas Gruenbacher
2020-06-17  0:32     ` Matthew Wilcox
2020-06-17  0:57       ` Andreas Grünbacher
2020-06-17  2:21         ` Matthew Wilcox
2020-06-18 12:46           ` Andreas Gruenbacher
2020-06-18 15:03             ` Matthew Wilcox
2020-06-18 16:40               ` Andreas Gruenbacher [this message]
2020-04-14 15:02 ` [PATCH v11 17/25] btrfs: Convert from readpages to readahead Matthew Wilcox
2020-04-14 15:02 ` [PATCH v11 18/25] erofs: Convert uncompressed files " Matthew Wilcox
2020-04-14 15:02 ` [PATCH v11 19/25] erofs: Convert compressed " Matthew Wilcox
2020-04-21  5:42   ` Andrew Morton
2020-04-21  7:28     ` Gao Xiang
2020-04-14 15:02 ` [PATCH v11 20/25] ext4: Convert " Matthew Wilcox
2020-04-14 15:02 ` [PATCH v11 21/25] ext4: Pass the inode to ext4_mpage_readpages Matthew Wilcox
2020-04-14 15:02 ` [PATCH v11 22/25] f2fs: Convert from readpages to readahead Matthew Wilcox
2020-04-14 15:02 ` [PATCH v11 23/25] f2fs: Pass the inode to f2fs_mpage_readpages Matthew Wilcox
2020-04-14 15:02 ` [PATCH v11 24/25] fuse: Convert from readpages to readahead Matthew Wilcox
2020-04-20 11:14   ` Miklos Szeredi
2020-04-20 11:43     ` Matthew Wilcox
2020-04-20 11:54       ` Miklos Szeredi
2020-04-14 15:02 ` [PATCH v11 25/25] iomap: " Matthew Wilcox

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