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