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Date:   Thu, 22 Aug 2019 08:59:27 -0400
From:   Vivek Goyal <vgoyal@redhat.com>
To:     Liu Bo <bo.liu@linux.alibaba.com>
Cc:     linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org,
        linux-nvdimm@lists.01.org, virtio-fs@redhat.com, miklos@szeredi.hu,
        stefanha@redhat.com, dgilbert@redhat.com,
        Miklos Szeredi <mszeredi@redhat.com>,
        Peng Tao <tao.peng@linux.alibaba.com>
Subject: Re: [PATCH 11/19] fuse, dax: Implement dax read/write operations
Message-ID: <20190822125927.GA8999@redhat.com>
References: <20190821175720.25901-1-vgoyal@redhat.com>
 <20190821175720.25901-12-vgoyal@redhat.com>
 <20190821194934.rqswgc52juisunl2@US-160370MP2.local>
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On Wed, Aug 21, 2019 at 12:49:34PM -0700, Liu Bo wrote:

[..]
> > +static int iomap_begin_upgrade_mapping(struct inode *inode, loff_t pos,
> > +					 loff_t length, unsigned flags,
> > +					 struct iomap *iomap)
> > +{
> > +	struct fuse_inode *fi = get_fuse_inode(inode);
> > +	struct fuse_dax_mapping *dmap;
> > +	int ret;
> > +
> > +	/*
> > +	 * Take exclusive lock so that only one caller can try to setup
> > +	 * mapping and others wait.
> > +	 */
> > +	down_write(&fi->i_dmap_sem);
> > +	dmap = fuse_dax_interval_tree_iter_first(&fi->dmap_tree, pos, pos);
> > +
> > +	/* We are holding either inode lock or i_mmap_sem, and that should
> > +	 * ensure that dmap can't reclaimed or truncated and it should still
> > +	 * be there in tree despite the fact we dropped and re-acquired the
> > +	 * lock.
> > +	 */
> > +	ret = -EIO;
> > +	if (WARN_ON(!dmap))
> > +		goto out_err;
> > +
> > +	/* Maybe another thread already upgraded mapping while we were not
> > +	 * holding lock.
> > +	 */
> > +	if (dmap->writable)
> > +		goto out_fill_iomap;
> 
> @ret needs to be reset here.
> 

Good catch. Will fix it.

Vivek