diff options
author | Amir Goldstein <amir73il@gmail.com> | 2017-04-24 00:25:49 +0300 |
---|---|---|
committer | Miklos Szeredi <mszeredi@redhat.com> | 2017-05-05 11:38:58 +0200 |
commit | 72b608f08528458334218a809d66ea94d924c378 (patch) | |
tree | 759ba4c56e36ceaa58e23d5e63bf461f20c868a3 /fs/overlayfs/inode.c | |
parent | b7a807dc2010334e62e0afd89d6f7a8913eb14ff (diff) |
ovl: constant st_ino/st_dev across copy up
When all layers are on the same underlying filesystem, let stat(2) return
st_dev/st_ino values of the copy up origin inode if it is known.
This results in constant st_ino/st_dev representation of files in an
overlay mount before and after copy up.
When the underlying filesystem support NFS exportfs, the result is also
persistent st_ino/st_dev representation before and after mount cycle.
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.
When all overlay layers are on the same fs, use overlay st_dev for non-dirs
to get the correct result from du -x.
Signed-off-by: Amir Goldstein <amir73il@gmail.com>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
Diffstat (limited to 'fs/overlayfs/inode.c')
-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; } |