Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752528AbcCUFDH (ORCPT ); Mon, 21 Mar 2016 01:03:07 -0400 Received: from imap.thunk.org ([74.207.234.97]:40026 "EHLO imap.thunk.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751435AbcCUFC4 (ORCPT ); Mon, 21 Mar 2016 01:02:56 -0400 Date: Mon, 21 Mar 2016 01:02:15 -0400 From: "Theodore Ts'o" To: Miklos Szeredi Cc: linux-kernel@vger.kernel.org, linux-fsdevel@vger.kernel.org, dhowells@redhat.com, viro@zeniv.linux.org.uk, Goldwyn Rodrigues , Trond Myklebust , stable@vger.kernel.org, Daniel Axtens Subject: Re: [PATCH 1/4] vfs: add file_dentry() Message-ID: <20160321050215.GD3331@thunk.org> Mail-Followup-To: Theodore Ts'o , Miklos Szeredi , linux-kernel@vger.kernel.org, linux-fsdevel@vger.kernel.org, dhowells@redhat.com, viro@zeniv.linux.org.uk, Goldwyn Rodrigues , Trond Myklebust , stable@vger.kernel.org, Daniel Axtens References: <1458205323-25685-1-git-send-email-miklos@szeredi.hu> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1458205323-25685-1-git-send-email-miklos@szeredi.hu> User-Agent: Mutt/1.5.24 (2015-08-30) X-SA-Exim-Connect-IP: X-SA-Exim-Mail-From: tytso@thunk.org X-SA-Exim-Scanned: No (on imap.thunk.org); SAEximRunCond expanded to false Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 4597 Lines: 132 On Thu, Mar 17, 2016 at 10:02:00AM +0100, Miklos Szeredi wrote: > From: Miklos Szeredi > > This series fixes bugs in nfs and ext4 due to 4bacc9c9234c ("overlayfs: Make > f_path always point to the overlay and f_inode to the underlay"). > > Regular files opened on overlayfs will result in the file being opened on > the underlying filesystem, while f_path points to the overlayfs > mount/dentry. > > This confuses filesystems which get the dentry from struct file and assume > it's theirs. > > Add a new helper, file_dentry() [*], to get the filesystem's own dentry > from the file. This simply compares file_inode(file->f_path.dentry) to > file_inode(file) and if they are equal returns file->f_path.dentry (this is > the common, non-overlayfs case). > > In the uncommon case (regular file on overlayfs) it will call into > overlayfs's ->d_native_dentry() to get the underlying dentry matching > file_inode(file). > > [*] If possible, it's better simply to use file_inode() instead. > > Signed-off-by: Miklos Szeredi > Tested-by: Goldwyn Rodrigues > Reviewed-by: Trond Myklebust > Cc: # v4.2 > Cc: David Howells > Cc: Al Viro > Cc: Theodore Ts'o > Cc: Daniel Axtens > --- > fs/open.c | 11 +++++++++++ > fs/overlayfs/super.c | 16 ++++++++++++++++ > include/linux/dcache.h | 1 + > include/linux/fs.h | 2 ++ > 4 files changed, 30 insertions(+) I have this patch in the ext4.git tree, but I'd like to get an Acked-by from Al before I send a pull request to Linus. Al? Any objections to my sending in this change via the ext4 tree? - Ted > > diff --git a/fs/open.c b/fs/open.c > index 55bdc75e2172..6326c11eda78 100644 > --- a/fs/open.c > +++ b/fs/open.c > @@ -831,6 +831,17 @@ char *file_path(struct file *filp, char *buf, int buflen) > } > EXPORT_SYMBOL(file_path); > > +struct dentry *file_dentry(const struct file *file) > +{ > + struct dentry *dentry = file->f_path.dentry; > + > + if (likely(d_inode(dentry) == file_inode(file))) > + return dentry; > + else > + return dentry->d_op->d_native_dentry(dentry, file_inode(file)); > +} > +EXPORT_SYMBOL(file_dentry); > + > /** > * vfs_open - open the file at the given path > * @path: path to open > diff --git a/fs/overlayfs/super.c b/fs/overlayfs/super.c > index 619ad4b016d2..5142aa2034c4 100644 > --- a/fs/overlayfs/super.c > +++ b/fs/overlayfs/super.c > @@ -336,14 +336,30 @@ static int ovl_dentry_weak_revalidate(struct dentry *dentry, unsigned int flags) > return ret; > } > > +static struct dentry *ovl_d_native_dentry(struct dentry *dentry, > + struct inode *inode) > +{ > + struct ovl_entry *oe = dentry->d_fsdata; > + struct dentry *realentry = ovl_upperdentry_dereference(oe); > + > + if (realentry && inode == d_inode(realentry)) > + return realentry; > + realentry = __ovl_dentry_lower(oe); > + if (realentry && inode == d_inode(realentry)) > + return realentry; > + BUG(); > +} > + > static const struct dentry_operations ovl_dentry_operations = { > .d_release = ovl_dentry_release, > .d_select_inode = ovl_d_select_inode, > + .d_native_dentry = ovl_d_native_dentry, > }; > > static const struct dentry_operations ovl_reval_dentry_operations = { > .d_release = ovl_dentry_release, > .d_select_inode = ovl_d_select_inode, > + .d_native_dentry = ovl_d_native_dentry, > .d_revalidate = ovl_dentry_revalidate, > .d_weak_revalidate = ovl_dentry_weak_revalidate, > }; > diff --git a/include/linux/dcache.h b/include/linux/dcache.h > index c4b5f4b3f8f8..99ecb6de636c 100644 > --- a/include/linux/dcache.h > +++ b/include/linux/dcache.h > @@ -161,6 +161,7 @@ struct dentry_operations { > struct vfsmount *(*d_automount)(struct path *); > int (*d_manage)(struct dentry *, bool); > struct inode *(*d_select_inode)(struct dentry *, unsigned); > + struct dentry *(*d_native_dentry)(struct dentry *, struct inode *); > } ____cacheline_aligned; > > /* > diff --git a/include/linux/fs.h b/include/linux/fs.h > index ae681002100a..1091d9f43271 100644 > --- a/include/linux/fs.h > +++ b/include/linux/fs.h > @@ -1234,6 +1234,8 @@ static inline struct inode *file_inode(const struct file *f) > return f->f_inode; > } > > +extern struct dentry *file_dentry(const struct file *file); > + > static inline int locks_lock_file_wait(struct file *filp, struct file_lock *fl) > { > return locks_lock_inode_wait(file_inode(filp), fl); > -- > 2.1.4 >