From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mx2.suse.de ([195.135.220.15]:35784 "EHLO mx1.suse.de" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1725886AbeGaWxO (ORCPT ); Tue, 31 Jul 2018 18:53:14 -0400 From: Mark Fasheh To: Al Viro , linux-fsdevel@vger.kernel.org Cc: linux-btrfs@vger.kernel.org, Andrew Morton , Amir Goldstein , linux-unionfs@vger.kernel.org, Jeff Mahoney , linux-nfs@vger.kernel.org, Mark Fasheh Subject: [PATCH 1/4] vfs: introduce function to map unique ino/dev pairs Date: Tue, 31 Jul 2018 14:10:42 -0700 Message-Id: <20180731211045.5671-2-mfasheh@suse.de> In-Reply-To: <20180731211045.5671-1-mfasheh@suse.de> References: <20180731211045.5671-1-mfasheh@suse.de> Sender: linux-fsdevel-owner@vger.kernel.org List-ID: There are places in the VFS where we export an ino/dev pair to userspace. /proc/PID/maps is a good example - we directly expose inode->i_ino and inode->i_sb->s_dev to userspace there. Many filesystems don't put a unique value in inode->i_ino and instead rely on ->getattr to provide the real inode number to userspace. super->s_dev is similar - some filesystems expose a difference device from what's put in super->s_dev when queried via stat/statx. Ultimately this makes it impossible for a user (or software) to match one of those reported pairs to the right inode. We can fix this by adding a helper function, vfs_map_unique_ino_dev(), which will query the owning filesystem (via ->getattr) to get the correct ino/dev pair. Later patches will update those places which simply dump inode->i_ino and super->s_dev to use the helper. Signed-off-by: Mark Fasheh --- fs/stat.c | 23 +++++++++++++++++++++++ include/linux/fs.h | 2 ++ 2 files changed, 25 insertions(+) diff --git a/fs/stat.c b/fs/stat.c index f8e6fb2c3657..80ea42505219 100644 --- a/fs/stat.c +++ b/fs/stat.c @@ -84,6 +84,29 @@ int vfs_getattr_nosec(const struct path *path, struct kstat *stat, } EXPORT_SYMBOL(vfs_getattr_nosec); +void vfs_map_unique_ino_dev(struct dentry *dentry, u64 *ino, dev_t *dev) +{ + int ret; + struct path path; + struct kstat stat; + + path.mnt = NULL; + path.dentry = dentry; + /* ->dev is always returned, so we only need to specify ino here */ + ret = vfs_getattr_nosec(&path, &stat, STATX_INO, 0); + if (ret) { + struct inode *inode = d_inode(dentry); + /* Fallback to old behavior in case of getattr error */ + *ino = inode->i_ino; + *dev = inode->i_sb->s_dev; + return ret; + } + *ino = stat.ino; + *dev = stat.dev; + return 0; +} +EXPORT_SYMBOL(vfs_map_unique_ino_dev); + /* * vfs_getattr - Get the enhanced basic attributes of a file * @path: The file of interest diff --git a/include/linux/fs.h b/include/linux/fs.h index d78d146a98da..b80789472438 100644 --- a/include/linux/fs.h +++ b/include/linux/fs.h @@ -3077,6 +3077,8 @@ extern void kfree_link(void *); extern void generic_fillattr(struct inode *, struct kstat *); extern int vfs_getattr_nosec(const struct path *, struct kstat *, u32, unsigned int); extern int vfs_getattr(const struct path *, struct kstat *, u32, unsigned int); +extern void vfs_map_unique_ino_dev(struct dentry *dentry, u64 *ino, dev_t *dev); + void __inode_add_bytes(struct inode *inode, loff_t bytes); void inode_add_bytes(struct inode *inode, loff_t bytes); void __inode_sub_bytes(struct inode *inode, loff_t bytes); -- 2.15.1