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authorAmir Goldstein <amir73il@gmail.com>2017-04-24 00:25:49 +0300
committerMiklos Szeredi <mszeredi@redhat.com>2017-05-05 11:38:58 +0200
commit72b608f08528458334218a809d66ea94d924c378 (patch)
tree759ba4c56e36ceaa58e23d5e63bf461f20c868a3 /fs/overlayfs/inode.c
parentb7a807dc2010334e62e0afd89d6f7a8913eb14ff (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.c39
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;
}