diff options
| -rw-r--r-- | fs/overlayfs/inode.c | 39 |
1 files changed, 38 insertions, 1 deletions
diff --git a/fs/overlayfs/inode.c b/fs/overlayfs/inode.c index 17b8418358ed..3dc693a78de2 100644 --- a/fs/overlayfs/inode.c +++ b/fs/overlayfs/inode.c @@ -61,14 +61,51 @@ static int ovl_getattr(const struct path *path, struct kstat *stat, u32 request_mask, unsigned int flags) { struct dentry *dentry = path->dentry; + enum ovl_path_type type; struct path realpath; const struct cred *old_cred; int err; - ovl_path_real(dentry, &realpath); + type = ovl_path_real(dentry, &realpath); old_cred = ovl_override_creds(dentry->d_sb); err = vfs_getattr(&realpath, stat, request_mask, flags); + if (err) + goto out; + + /* + * When all layers are on the same fs, all real inode number are + * unique, so we use the overlay st_dev, which is friendly to du -x. + * + * We also use st_ino of the copy up origin, if we know it. + * This guaranties constant st_dev/st_ino across copy up. + * + * If filesystem supports NFS export ops, this also guaranties + * persistent st_ino across mount cycle. + */ + if (ovl_same_sb(dentry->d_sb)) { + if (OVL_TYPE_ORIGIN(type)) { + struct kstat lowerstat; + + ovl_path_lower(dentry, &realpath); + err = vfs_getattr(&realpath, &lowerstat, + STATX_INO | STATX_NLINK, flags); + if (err) + goto out; + + WARN_ON_ONCE(stat->dev != lowerstat.dev); + /* + * Lower hardlinks are broken on copy up to different + * upper files, so we cannot use the lower origin st_ino + * for those different files, even for the same fs case. + */ + if (lowerstat.nlink == 1) + stat->ino = lowerstat.ino; + } + stat->dev = dentry->d_sb->s_dev; + } +out: revert_creds(old_cred); + return err; } |